掺杂对庞磁电阻材料本征性质的影响
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摘要
钙钛矿锰氧化物由于在居里温度Tc附近表现出庞磁电阻效应(CMR),具有100 %自旋极化率及存在着复杂的电子、晶格、自旋等相互作用而成为凝聚态物理、材料物理等领域的主要研究对象之一。双交换作用是解释钙钛矿锰氧化物电输运行为和磁性质的重要理论,但是,掺杂怎样影响双交换作用以及异性离子间是否有铁磁作用一直是一个未解决的问题。本论文主要以钙钛矿锰氧化物La_(2/3)Ca_(1/3)MnO_3、La_(2/3)Sr_(1/3)MnO_3为研究对象,通过在其A位和B位进行特殊形式的掺杂,对掺杂体系的电输运和磁性质进行研究,从而为掺杂如何影响双交换作用、异性离子间是否有铁磁作用以及提高室温处的磁电阻效应提供实验和理论研究基础。主要研究内容包括如下几方面:
1.介绍了磁电子学的相关内容,对最具应用前景的磁电子材料——钙钛矿锰氧化物的结构、电输运行为与磁性质进行了较全面的概括,综述了钙钛矿锰氧化物中掺杂对双交换和本征磁电阻的影响,在此基础上提出了论文的选题依据和研究意义。
2.在A位掺杂研究中,通过改变A位平均离子半径以及固定改变失配因子σ2,研究了掺杂对双交换作用的影响以及样品的居里温度和CMR的变化规律。实验发现随着的减小,或者固定时随着σ2的增加,Mn-O-Mn键键角小于180o,双交换作用被削弱。因此,样品的Tc降低而CMR增大。
3. Cr~(3+)具有和Mn~(4+)相同的电子组态,因此Cr~(3+)与Mn~(3+)间是否具有双交换作用是一个未解决的问题。通过保持[Mn~(3+)]/([Mn~(4+)]+[Cr~(3+)])之比为择优比例2:1,采用特殊形式的B位Cr掺杂,制备了样品La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3,并和采用通常的掺杂方式样品La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3进行了电输运和磁性质的比较研究。实验发现Cr的掺杂对样品的Tc和绝缘体-金属转变温度Tp的下降影响较小;在低掺杂量时,La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3的电阻-温度曲线有“双峰”现象,而La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3的电阻-温度曲线没有“双峰”现象。同时,与La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3比较,La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3的磁化强度和导电性在低温区域增强。我们提出在Tc附近的高温区域,Mn~(3+)与Cr~(3+)之间存在着非常弱的双交换作用。但是当温度降低,这种铁磁作用导致Mn~(3+)与Cr~(3+)平行排列,因此Mn~(3+)与Cr~(3+)之间存在着的弱的双交换作用增强;所以在Mn~(3+)与Cr~(3+)间就有可能的电子传输,这将增强样品的电导。Mn~(3+)-O-Cr~(3+)间的作用类似于Mn~(3+)-O-Mn~(4+)间的双交换作用但比后者要弱一些。
4.同样,当掺杂量y≤0.1时,La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3的电阻-温度曲线有“双峰”现象,而La_(2/3+y)Sr_(1/3-y)Mn_(1-y)Cr_yO_3的电阻-温度曲线没有双峰现象。与La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3比较,La_(2/3+y)Sr_(1/3-y)Mn_(1-y)Cr_yO_3的导电性在低温区域增强,而且其室温附近的CMR比采用通常掺杂方式的样品有较大幅度的提高。这可能是因为Mn~(3+)与Cr~(3+)之间存在着的弱的双交换作用随温度降低和磁场的作用增强引起的CMR的提高。
5.保持Mn~(3+)与Mn~(4+)的比例为2:1,采用La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3的形式掺杂,并和采用通常掺杂方式的样品La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3进行了比较研究。实验发现Cu在La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3中有助熔作用,但是在La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3中则没有。由于助熔作用,La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3的Tp几乎不下降,且磁电阻没有明显的增强;La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3电阻率及其峰值随着掺杂量的增加而增加,而且Tp也随之下降,磁电阻在较宽的温度范围内均得到了增强。
6. Cu对La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3和La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3都没有明显的助熔作用。随掺杂量y增加,样品Tp降低,电阻率升高。La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3磁电阻值比La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3有较大幅度的提高,在室温附近有较大的磁电阻效应。
7. La_((2+4y)/3)(Ca,Sr)_((1-4y)/3)Mn_(1-y)Cu_yO_3的Tc和Tp都低于样品La_(2/3)(Ca,Sr)_(1/3)Mn_(1-y)Cu_yO_3的值,可见保持Mn~(3+)与Mn~(4+)的比例为2:1并没有使La_((2+4y)/3)(Ca,Sr)_((1-4y)/3)Mn_(1-y)Cu_yO_3具有较好的铁磁性。这说明A位上两种元素的比例变化导致的容忍因子t、和σ~2的改变也是影响双交换的重要因素。
总之,以钙钛矿锰氧化物为基体,通过特殊设计的A位和B位掺杂方式,在一定程度上能阐明A位变化对双交换作用的影响及B位异性离子间是否有铁磁作用。这一方法为研究钙钛矿锰氧化物中的双交换理论提供了一个全新的思路,也能为寻求室温磁电阻材料提供参考。
Peroveskite Manganites are the subject of intense study for the fields of condensed physics and materials physics in recent years due to the discovery of colossal Magnetoresistance (CMR) effect near Curie Temperature Tc and 100% spin polarization, as well as the complex interaction between electrons,lattices and spins in these compounds. Double Exchange (DE) is an important theory in interpretation of the electrical transport and magnetic properties of manganites. However, the effect of doping on DE and the possibility of DE hetero-ionic coupling between Mn and other ions has not yet been conclusive, and remains an open question. In this thesis, we base on the polycrystalline manganese oxides of La_(2/3)Ca_(1/3)MnO_3 and La_(2/3)Sr_(1/3)MnO_3, introduce the foreign elements to A- and B-sites by a special method. The electrical transport and magnetic properties of the doped manganites have been investigated, which provides experimental and theoretic basis for the enhancement of CMR at room temperature and whether or not DE coupling between hetero-ionic. The main investigations are shown as followed:
1. An introduction of spintronics has been presented. More attentions have been paid on the structure, electrical transport behavior, and magnetic properties of perovskite manganites, which are considered as the most promising magneto electronics materials. On the basis of the effect to DE and CMR by substituting in perovskite manganites, the basic thinking of subject selection and investigation significance is put forward.
2. A series of samples have been prepared by decreasing the value of and by fixing and increasingσ~2, in order to study the effect to DE and CMR by substituting at A-sites. It is found that the angle of Mn-O-Mn bond deviates 180o and the DE is weaken with the decreasing and increasingσ~2, which results in the decrease of T_c and an enhancement of CMR.
3. Cr~(3+) has the same electronic configuration as Mn~(4+), so whether or not DE coupling between them remains an open question. A special formula of La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3 with [Mn~(3+)]/([Mn~(4+)]+[Cr~(3+)]) ratio fixed at optimal proportion 2:1 is designed and a comparison of the magnetic and electrical transport properties with La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3. It is found that the substituting Cr for Mn in manganites shows inefficiency in lowering Tc and Tp. At lower doping level, there are two peaks in the resistivity versus temperature curve for La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3 and the additional peak disappears for La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3. Compared with La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3, the magnetization and conductivity are enhanced in La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3 in the low temperature range. we suggest that there exists the poor DE between Mn~(3+) and Cr~(3+) coupling at high temperature so that Cr~(3+) cannot play the role of Mn~(4+) in the Mn~(3+)-O-Cr~(3+) interaction. With the decrease in temperature, Cr~(3+) partially plays the role of Mn~(4+) in the Mn~(3+)-O-Cr~(3+) interaction, Mn~(3+) and Cr~(3+) ions turn to be favor of ferromagnetically ordering, probability of the electron transfer between Mn~(3+) and Cr~(3+) ions increases, which would promote the conductivity. The DE interaction between Mn~(3+) and Cr~(3+) is similar to the DE interaction between Mn~(3+) and Mn~(4+) but the former is weaker than that for the latter.
4. Similarly, at y≤0.1, the resistivity versus temperature curve for La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3 displays double peaks, however, there has an intrinsic characteristic peak in the curve of La_(2/3+y)Sr_(1/3-y)Mn_(1-y)Cr_yO_3. Compared with La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3, the conductivity is enhanced in La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3 in the low temperature range. Furthermore, there is a visible enhancement of CMR around room temperature, which corresponds with the enhancement of the DE interaction between Mn~(3+) and Cr~(3+) with a decreasing in temperature.
5. A series of double-doping samples of La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3 with the Mn~(3+)/Mn~(4+) ratio fixed at 2:1 have been prepared and compared to La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3 by the measurement of the structural, magnetic and electrical transport properties. It is found that Cu doping acts the role of fluxing action in La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3 but cannot act it in La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3. The Tp of La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3 maintains around the Tp of La_(2/3)Ca_(1/3)MnO_3, but the Tp of La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3 shifts towards lower temperature with the increasing of the doping content, meanwhile, the magnetoresistance of La_((2+4y)/3)Ca _((1-4y)/3)Mn_(1-y)Cu_yO_3 is enhanced at a wide temperature window.
6. In the samples La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3 and La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3, Cu doping cannot act the role of fluxing action in those manganites. The Tp of all samples shift towards lower temperature region with the increasing of doping content and the resistivity increase. Compared to La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3, the CMR effect is enhanced in La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3 especially at the room temperature region.
7. The Tc and Tp of La_((2+4y)/3)(Ca,Sr)_((1-4y)/3)Mn_(1-y)Cu_yO_3 are lower than that of La_(2/3)(Ca,Sr)_(1/3)Mn_(1-y)Cu_yO_3, which implies that the ratio of Mn~(3+)/Mn~(4+) maintained at 2:1 except for Cu2+ cannot make samples a good ferromagnetism. The influence of tolerance factor, andσ2 by altering the ratio of A-sites elements on magnetic properties and DE may be the main factor for the double-doping manganites.
As a conclusion, the special doping method on A- and B-sites in manganites is a distinct technique to clarify the influence on DE and experimentally test the possibility of DE hetero-ionic coupling between Mn and other ions in a certain extent. Such a process presents a new way to study DE in manganites, which would be beneficial to search out the room temperature magnetoresistance materials also.
1.介绍了磁电子学的相关内容,对最具应用前景的磁电子材料——钙钛矿锰氧化物的结构、电输运行为与磁性质进行了较全面的概括,综述了钙钛矿锰氧化物中掺杂对双交换和本征磁电阻的影响,在此基础上提出了论文的选题依据和研究意义。
2.在A位掺杂研究中,通过改变A位平均离子半径
3. Cr~(3+)具有和Mn~(4+)相同的电子组态,因此Cr~(3+)与Mn~(3+)间是否具有双交换作用是一个未解决的问题。通过保持[Mn~(3+)]/([Mn~(4+)]+[Cr~(3+)])之比为择优比例2:1,采用特殊形式的B位Cr掺杂,制备了样品La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3,并和采用通常的掺杂方式样品La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3进行了电输运和磁性质的比较研究。实验发现Cr的掺杂对样品的Tc和绝缘体-金属转变温度Tp的下降影响较小;在低掺杂量时,La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3的电阻-温度曲线有“双峰”现象,而La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3的电阻-温度曲线没有“双峰”现象。同时,与La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3比较,La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3的磁化强度和导电性在低温区域增强。我们提出在Tc附近的高温区域,Mn~(3+)与Cr~(3+)之间存在着非常弱的双交换作用。但是当温度降低,这种铁磁作用导致Mn~(3+)与Cr~(3+)平行排列,因此Mn~(3+)与Cr~(3+)之间存在着的弱的双交换作用增强;所以在Mn~(3+)与Cr~(3+)间就有可能的电子传输,这将增强样品的电导。Mn~(3+)-O-Cr~(3+)间的作用类似于Mn~(3+)-O-Mn~(4+)间的双交换作用但比后者要弱一些。
4.同样,当掺杂量y≤0.1时,La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3的电阻-温度曲线有“双峰”现象,而La_(2/3+y)Sr_(1/3-y)Mn_(1-y)Cr_yO_3的电阻-温度曲线没有双峰现象。与La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3比较,La_(2/3+y)Sr_(1/3-y)Mn_(1-y)Cr_yO_3的导电性在低温区域增强,而且其室温附近的CMR比采用通常掺杂方式的样品有较大幅度的提高。这可能是因为Mn~(3+)与Cr~(3+)之间存在着的弱的双交换作用随温度降低和磁场的作用增强引起的CMR的提高。
5.保持Mn~(3+)与Mn~(4+)的比例为2:1,采用La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3的形式掺杂,并和采用通常掺杂方式的样品La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3进行了比较研究。实验发现Cu在La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3中有助熔作用,但是在La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3中则没有。由于助熔作用,La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3的Tp几乎不下降,且磁电阻没有明显的增强;La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3电阻率及其峰值随着掺杂量的增加而增加,而且Tp也随之下降,磁电阻在较宽的温度范围内均得到了增强。
6. Cu对La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3和La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3都没有明显的助熔作用。随掺杂量y增加,样品Tp降低,电阻率升高。La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3磁电阻值比La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3有较大幅度的提高,在室温附近有较大的磁电阻效应。
7. La_((2+4y)/3)(Ca,Sr)_((1-4y)/3)Mn_(1-y)Cu_yO_3的Tc和Tp都低于样品La_(2/3)(Ca,Sr)_(1/3)Mn_(1-y)Cu_yO_3的值,可见保持Mn~(3+)与Mn~(4+)的比例为2:1并没有使La_((2+4y)/3)(Ca,Sr)_((1-4y)/3)Mn_(1-y)Cu_yO_3具有较好的铁磁性。这说明A位上两种元素的比例变化导致的容忍因子t、
总之,以钙钛矿锰氧化物为基体,通过特殊设计的A位和B位掺杂方式,在一定程度上能阐明A位变化对双交换作用的影响及B位异性离子间是否有铁磁作用。这一方法为研究钙钛矿锰氧化物中的双交换理论提供了一个全新的思路,也能为寻求室温磁电阻材料提供参考。
Peroveskite Manganites are the subject of intense study for the fields of condensed physics and materials physics in recent years due to the discovery of colossal Magnetoresistance (CMR) effect near Curie Temperature Tc and 100% spin polarization, as well as the complex interaction between electrons,lattices and spins in these compounds. Double Exchange (DE) is an important theory in interpretation of the electrical transport and magnetic properties of manganites. However, the effect of doping on DE and the possibility of DE hetero-ionic coupling between Mn and other ions has not yet been conclusive, and remains an open question. In this thesis, we base on the polycrystalline manganese oxides of La_(2/3)Ca_(1/3)MnO_3 and La_(2/3)Sr_(1/3)MnO_3, introduce the foreign elements to A- and B-sites by a special method. The electrical transport and magnetic properties of the doped manganites have been investigated, which provides experimental and theoretic basis for the enhancement of CMR at room temperature and whether or not DE coupling between hetero-ionic. The main investigations are shown as followed:
1. An introduction of spintronics has been presented. More attentions have been paid on the structure, electrical transport behavior, and magnetic properties of perovskite manganites, which are considered as the most promising magneto electronics materials. On the basis of the effect to DE and CMR by substituting in perovskite manganites, the basic thinking of subject selection and investigation significance is put forward.
2. A series of samples have been prepared by decreasing the value of
3. Cr~(3+) has the same electronic configuration as Mn~(4+), so whether or not DE coupling between them remains an open question. A special formula of La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3 with [Mn~(3+)]/([Mn~(4+)]+[Cr~(3+)]) ratio fixed at optimal proportion 2:1 is designed and a comparison of the magnetic and electrical transport properties with La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3. It is found that the substituting Cr for Mn in manganites shows inefficiency in lowering Tc and Tp. At lower doping level, there are two peaks in the resistivity versus temperature curve for La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3 and the additional peak disappears for La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3. Compared with La_(2/3)Ca_(1/3)Mn_(1-y)Cr_yO_3, the magnetization and conductivity are enhanced in La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3 in the low temperature range. we suggest that there exists the poor DE between Mn~(3+) and Cr~(3+) coupling at high temperature so that Cr~(3+) cannot play the role of Mn~(4+) in the Mn~(3+)-O-Cr~(3+) interaction. With the decrease in temperature, Cr~(3+) partially plays the role of Mn~(4+) in the Mn~(3+)-O-Cr~(3+) interaction, Mn~(3+) and Cr~(3+) ions turn to be favor of ferromagnetically ordering, probability of the electron transfer between Mn~(3+) and Cr~(3+) ions increases, which would promote the conductivity. The DE interaction between Mn~(3+) and Cr~(3+) is similar to the DE interaction between Mn~(3+) and Mn~(4+) but the former is weaker than that for the latter.
4. Similarly, at y≤0.1, the resistivity versus temperature curve for La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3 displays double peaks, however, there has an intrinsic characteristic peak in the curve of La_(2/3+y)Sr_(1/3-y)Mn_(1-y)Cr_yO_3. Compared with La_(2/3)Sr_(1/3)Mn_(1-y)Cr_yO_3, the conductivity is enhanced in La_(2/3+y)Ca_(1/3-y)Mn_(1-y)Cr_yO_3 in the low temperature range. Furthermore, there is a visible enhancement of CMR around room temperature, which corresponds with the enhancement of the DE interaction between Mn~(3+) and Cr~(3+) with a decreasing in temperature.
5. A series of double-doping samples of La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3 with the Mn~(3+)/Mn~(4+) ratio fixed at 2:1 have been prepared and compared to La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3 by the measurement of the structural, magnetic and electrical transport properties. It is found that Cu doping acts the role of fluxing action in La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3 but cannot act it in La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3. The Tp of La_(2/3)Ca_(1/3)Mn_(1-y)Cu_yO_3 maintains around the Tp of La_(2/3)Ca_(1/3)MnO_3, but the Tp of La_((2+4y)/3)Ca_((1-4y)/3)Mn_(1-y)Cu_yO_3 shifts towards lower temperature with the increasing of the doping content, meanwhile, the magnetoresistance of La_((2+4y)/3)Ca _((1-4y)/3)Mn_(1-y)Cu_yO_3 is enhanced at a wide temperature window.
6. In the samples La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3 and La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3, Cu doping cannot act the role of fluxing action in those manganites. The Tp of all samples shift towards lower temperature region with the increasing of doping content and the resistivity increase. Compared to La_(2/3)Sr_(1/3)Mn_(1-y)Cu_yO_3, the CMR effect is enhanced in La(2+4y)/3Sr(1-4y)/3Mn_(1-y)Cu_yO_3 especially at the room temperature region.
7. The Tc and Tp of La_((2+4y)/3)(Ca,Sr)_((1-4y)/3)Mn_(1-y)Cu_yO_3 are lower than that of La_(2/3)(Ca,Sr)_(1/3)Mn_(1-y)Cu_yO_3, which implies that the ratio of Mn~(3+)/Mn~(4+) maintained at 2:1 except for Cu2+ cannot make samples a good ferromagnetism. The influence of tolerance factor,
As a conclusion, the special doping method on A- and B-sites in manganites is a distinct technique to clarify the influence on DE and experimentally test the possibility of DE hetero-ionic coupling between Mn and other ions in a certain extent. Such a process presents a new way to study DE in manganites, which would be beneficial to search out the room temperature magnetoresistance materials also.
引文
[1]蔡建旺,赵见高,詹文山等.磁电子学中的若干问题.物理学进展, 1997, 17 (2) : 119-141.
[2] Gary A. Prinz. Magnetoelectronics. Science, 1998, 282 (27) : 1660-1663.
[3] Wolf S A, Awschalom D D, Buhrman R A, et al. Spintronics: A spin-based electronics vision for the future. Science, 2001, 294 (16) : 1488-1495.
[4] Park J H, Vescovo E, Kim H J, et al. Direct evidence for a half-metallic ferromagnet. Nature, 1998, 392 (23) : 794-796.
[5] Hwang H Y, Cheong S W, Ong N P, et al. Spin-polarized intergrain tunneling in La2/3Sr1/3MnO3. Phys. Rev. Lett . 1996 , 77 (10) : 2041-2044.
[6] von Helmolt R, Wecker J, Holzapfel B, et al. Giant negative magnetoresistance in perovskite like La2/3Ba1/3MnO3 ferromagnetic films. Phys. Rev. Lett., 1993, 71 (14) : 2331-2333.
[7] Jin S, Tiefel T H, McCormack M, et al. Thousandfold change in resistivity in magnetoresistive La-Ca-Mn-O films. Science, 1994, 264 (5157) : 413-415.
[8] Booth C H, Bridges F, Kwei G H, et al. Direct relationship between magnetism and MnO6 distortions in La1-xCaxMnO3. Phys. Rev. Lett., 1998, 80 (4) : 853-856.
[9] Uhlenbruck S, Teipen R, Klingeler R,et al. Interplay between charge order, magnetism, and structure in La0.875Sr0.125MnO3. Phys. Rev. Lett., 1998, 82: 185-187.
[10] Li X W, Gupta A, Xiao G, et al. Low-field magnetoresistive properties of polycrystalline and epitaxial perovskite manganite films. Appl. Phys. Lett., 1997, 71 (8) : 1124-1126.
[11] Schiffer P, Ramirez A P, Bao W, et al. Low field magnetoresistance and the magnetic phase-diagram of La1-xCaxMnO3. Phys. Rev. Lett., 1995, 75 (18) : 3336-3339.
[12] Zhang N, Ding W P, Zhong W, et al. Tunnel-type giant magntoresistance in the granular perovskite La0.85Sr0.15MnO3. Phys. Rev. B, 1997, 56 (13) : 8138-8142.
[13] Gupta A, Gong G Q, Xiao G, et al. Grain-boundary effects on the magnetoresistance properties of perovskite manganite films. Phys. Rev. B, 1996, 54 (22) : R15629-R15632.
[14] Yakel H L. On the structure of some compounds of the perovskite type. Acta Crystallogr, 1955, 8 (7) : 394-398.
[15] Goodenough J B, Longon J M, Tabellen B L. New Series, GroupⅢ(4), Pt, a Springer, Berlin,1970.
[16] Goodenough J B. Colossal magnetoresistance in Ln1-xAxMnO3 perovskite. Aust. J. Phys., 1999, 52 (2) : 155-186.
[17] Goodenough J B. Electronic structure of CMR manganites. J. Appl. Phys., 1997, 81 (8) : 5330-5335.
[18] Haghiri-Gosnet A M, Renard J P, CMR manganites: physics, thin films and devices. J. Phys. D: Appl. Phys., 2003, 36 : R127-150.
[19] Millis A. J, Littlewood P B, Shraiman B I. Double exchange alone doesnot explain the resistivity of La1-xSrxMnO3. Phys. Rev. Lett., 1995, 74 (25) : 5144–5147.
[20] Goodenough J B. In magnetism and the chemical bond, Interscience, New York, 1963, Chap. 3.
[21] Argyriou D N, Mitchell J F, Patter C D, et al. Lattice effects and magnetic order in the canted ferromagnetic insulator La0.875Sr0.125MnO3. Phys. Rev. Lett., 1996, 76 (20) : 3826-3829.
[22] Pickett W E, Singh J. Electronic structure and half-metallic transport in the La1-xCaxMnO3 system. Phys. Rev. B, 1996, 53 (3) : 1146-1160.
[23] Cheong S W, Hwang H Y. Contribution to colossal magnetoresistance oxides. In: Tokura, Monographs in Condensed Matter Science Gordon & Breach, London 1999.
[24] Anderson P W, Hasegawa H. Considerations on double exchange. Phys. Rev., 1955, 100 (2) : 675-681.
[25] Jonker G H, Van Santen J H. Low temperature magnetoresistance and the magneticphase diagram of La1-xCaxMnO3. Physica, 1950, 16 (3) : 337-383.
[26] de Gennes P G. Effects of double exchange in magnetic crystals. Phys. Rev. 1960, 118 (1) : 141-154.
[27] Wu G R. Inoue M, Sasaki M, et al. Carrier generation/reombination processes and polaron effect in pervoskite manganite thin film. Physics B, 2000, 284 (2) : 1912-1913.
[28] Mott N F, Davis E A. Electronic Processes in Non Crystalline Material. Oxford: Oxford University Press, 1979, 52-56.
[29] Jia Y X, Lu L. Pr-doping of high-magnetoresistance perovskite Nd2/3Sr1/3MnO3. Solid State Communnication, 1995, 94 (11) : 917-921.
[30] Guo Z B, Zhang J R, Zhang N, et al. Electrical properties of La0.7-xPrxSr0.3MnO3 pervoskites. Appl. Phys. Lett., 1997, 70 (14) : 1897-1899.
[31] Gong G Q, Canedy C, Xiao G. Colossal magnetoresistance of 1000000 fold magnitude achieved in the antiferromagnetic phase of La1-xCaxMnO3, Appl. Phys. Lett., 1995, 67:1783-1785.
[32] Hwang H Y, Cheong S W, Ong N P, et al. Lattice effects on the magnetoresistance in doped LaMnO3. Phys. Rev. Lett., 1995, 75:914-919.
[33] Dagotto E, Hotta T, Moreo A. Colossal magnetoresistant materials: The key role of phase separation. Phys. Rep. 2001, 344 (1-3) : 1-153.
[34] Moreo A,Seiji Y, Elbio D. Phase separation secenario for manganese oxidex and related materials. Science, 1999, 283 (26) : 2034-2040.
[35] Wollan E O, Koehler W C. Neutron diffraction study of the magnetic properties of the series of perovskite-type compounds [(1-x) La, xCa]MnO3. Phys. Rev., 1955, 100 (2) : 545-563.
[36] Liu K, Wu X W, Ahn K H, et al. Charge ordering and magnetoresistance in Nd1-xCaxMnO3 due to reduced double exchange. Phys. Rev. B, 1996, 54:3007-3010
[37] Tokura Y, Tomioka Y. Origins of colossal magnetoresistance in perovskite-typemanganese oxides. J. Appl. Phys., 1996, 79:5288-5291.
[38] Gong G Q, Canedy C L, Xiao G. Colossal magnetoresistance in the antiferromagnetic La0.5Ca0.5MnO3 system. J. Appl. Phys. 1996, 79: 4538-4540.
[39] Radaelli P G, Cox D E, Marezio M, et al. Simultaneous structure, magnetic, and eletronictransitions in La1-xCaxMnO3 with x = 0.25 and 0.5. Phys. Rev. Lett., 1995, 75(24): 4488-4491.
[40] Balagurov A M, Pomjakushin V Yu, Sheptyakov D V, et al. Long-scale phase separation versus homogeneous magnetic state in (La1-yPry)0.7Ca0.3MnO3: A neutron diffraction study. Phys. Rev. B, 2001, 64(2):024420/1-10.
[41] Yuan S L, Liu J, Xia Z C, et al. Correction to the metal-insulator transition due to cation size and strain effect for colossal magnetoresistance perovskites. Chin. Phys. Lett, 2002, 19:1675-1678.
[42] F?th M, Freisem S, Menovsky A A, et al. Spatially inhomogeneous metal-insulator transition in doped manganites. Science, 1999, 285 (5433) :1540-1542.
[43] Rodriguez-Martinez L M, Attfield J P. Cation disorder and the metal-insulator transition temperature in manganese oxide perovskites . Phys. Rev. B, 1998, 58(5):2426-2431.
[44] Rodriguez-Martinez L M, Attfield J P. Disorder-induced orbital ordering in L0.7M0.3MnO3 perovskites. Phys. Rev. B, 2000, 63(2): 024424-024430.
[45] Meskine H, K?nig H, Satpathy S. Orbital ordering and exchange interaction in the manganites. Phys. Rev. B, 2001, 64(9): 094433/1-13.
[46] Zhou J S, Goodenough J B. Dynamic Jahn-Teller distortions and thermal conductivity in La1-xSrxMnO3 crystals. Phys. Rev .B, 2001, 64(2):024421-024424.
[47] Rivadulla F, López-Quintela M A, Mira J, et al. Jahn-Teller vibrational anisotropy determines the magnetic structure in orthomanganites. Phys. Rev .B, 1998, 64(5):052403-052407.
[48] Rodriguez-Martinez L M, Attfield J P. Cation disorder and size effects in magnetoresistive manganese oxide perovskites. Phys.Rev.B. 1996, 54: 15622-15625.
[49] Mathieu R, Akahoshi D, Asamitsu A, et al. Colossal magnetoresistance without phase separtation: disorder-induced spin glass state and nanometer scale orbital-charge correlation in half doped manganites. Phys.Rev.Lett., 2004, 93:227202-227206.
[50] Zener C. Interaction between the d-shell in the transition metal. II. ferromagnetic compounds of manganese with pervoskite structure. Phys. Rev. 1951, 82 : 403-405.
[51] Anderson P W, Hasegawa H. Considerations on double exchange. Phys. Rev., 1955, 100 (2) : 675-681.
[52] Searle C W, Wang S T. Magnetic properties in La0.69Pb0.31MnO3. J. Phys., 1970, 48 (17) : 2023-2031.
[53] Calderon M J, Verges J A , Brey L. Conductance as a function of temperature in the double-exchange model. Phys. Rev. B, 1999, 59(6): 4170-4175.
[54] Ishizaka S, Ishihara S. Temperature dependence of the resistivity in the double-exchange model. Phys. Rev. B, 1999, 59(13): 8375-8378.
[55] Snyder G J, Hiskes R, Dicarolis S, et al. Intrinsic electrical transport and magnetocproperties of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 MOCVD thin films and bulk material. Phys. Rev. B, 1996, 53 (21) : 14434-14444.
[56] Jaime M, Lin P, Salamon M B, et al. Low-temperature electrical transport and double exchange in La0.67(Pb,Ca)0.33MnO3. Phys. Rev. B, 1998, 58: R5901-5904.
[57] Alonso J L, Fernandez L A, Guinea F, et al. Discontinuous transitions in double-exchange materials. Phys. Rev. B, 2001, 63:064416/1-7.
[58] Millis A J, Shraiman B I, Mueller R. Dynamic Jahn-Teller Effect and Colossal Magnetoresistance in La1-xSrxMnO3. Phys. Rev. Lett.,1996, 77 :175-178.
[59] Millis A J, Mueller R, Shraiman B I. Fermi-liquid-to-polaron crossover. I. General results. Phys. Rev. B 1996 54: 5389-5393.
[60] Millis A J, Mueller R, Shraiman B I. Fermi-liquid-to-polaron crossover. II. Double exchange and the physics of colossal magnetoresistance. Phys. Rev. B, 1996, 54: 5405-5409.
[61] Coey J M D, Viret M, von Molnar S. Mixed-valence manganites. Adv. Phys. 1999, 48 (2) : 167-256.
[62] McCormack M, Jin S, Tiefel T H, et al. Very large magnetoresistance in perovskite-like La-Ca-Mn-O thin films. Appl. Phys. Lett., 1994, 64 (22) : 3045-3047.
[63] Jin S, Obryan H M, Tiefel T H, et al. Large magnetoresistance in ploycrystalline La-Ca-Mn-O, Appl. Phys. Lett., 1995, 66 (3) : 382-384.
[64] Tokura Y, Urushibara A, Moritomo Y, et al. Giant magnetotransport phenomena in filling-controlled kondo lattice system: La1-xSrxMnO3. J. Phys. Soc. Japan, 1994, 63 (11) : 3931-3938.
[65] Urushibara A, Moritomo Y, Arima T, et al. Insulator-metal transition and giant magnetoresistance in La1-xCaxMnO3. Phys. Rev. B, 1995, 51 (20) : 14103-14109.
[66] Fontcuberta J, Martnez B, Seffar A, et al. Colossal magnetoresistance of ferromagnetic manganites: structure tuning and mechanisms. Phys. Rev. Lett., 1996, 76 (7) : 1122-1125.
[67] O'Donnell J, Onellion M, Rzchowski M S, et al. magnetoresistance scalling in MBE-grown La0.7Ca0.3MnO3 thin films. Phys. Rev. B, 1996, 54 (10) : R6841-R6844.
[68] Tomioka Y, Asamitsu A, Tokura Y. Magnetotransport properties and magnetostructure phenomenon in single crystals of La0.7(Ca1-ySry)0.3MnO3. Phys. Rev. B, 2001 63 (2) : 024421/1-6.
[69] Yuan S L, Tang J, Xia Z C, et al. Low-field colossal constant magnetoresistance for wide temperature ranges in the sol-gel prepared La2/3Ca1/3Mn0.96Cu0.04O3. Solid State Comm., 2003, 127 : 743-747.
[70] Nunez-Regueiro J E, Kadin A M. Phenomenological Model for Giant Magnetoresistance in Lanthanum Manganite. Applied Physics Letters, 1996, 68 (19) : 2747 -2749.
[71] Coey J M D, Viret M, Ranno L. Electron localization in mixed-valence manganites. Phy. Rev. Lett., 1995, 75 (21) : 3910-3913.
[72] Viret M, Ranno L, Coey J M D. Magnetic localization in mixed-valence manganites. Physical Review B, 1997, 55 (13) : 8067-8070.
[73] Zhang S F. Electrical conductivity in ferromagnetic perovskita structures. J. Appl. Phys., 1996, 79 (8) : 4542- 4544.
[74] Millis A J. Lattice effects in magnetoresistive manganese perovskites. Nature, 1998, 392 (12) : 147-150.
[75] Mott N F. Conduction in non-crystalline materials, Oxford University Press, New York, 1993, 1-285.
[76] Ziese M, Srinitiwarawong C. Polaronic effects on the resistivity of manganite thin films. Phys. Rev. B,1998, 58 :11519-11525.
[77] Jaime M, Salamon M B, Rubinstein M, et al. High-temperature thermopower in La2/3Ca1/3MnO3 films: Evidence for polaronic transport. Phys. Rev. B,1996, 54:11914-11918.
[78] Palstra T T M, Ramirez A P, Cheong S W, et al. Transport mechanisms in doped LaMnO3: Evidence for polaron formation. Phys. Rev. B, 1997, 56 :5104-5107.
[79] Jaime M, Hardner H T, Salamon M B, et al. Hall-Effect Sign Anomaly and Small-Polaron Conduction in (La1-xGdx)0.67Ca0.33MnO3. Phys. Rev. Lett. 1997, 78: 951-954.
[80] Wang L, Yin J, Huang S, et al. Thermally activated drift mobility and small polaron conduction in La0.75Sr0.11Ca0.14MnO3 thin films investigated by the traveling wave method. Phys. Rev. B,1999, 60: R6976-6980.
[81] Adams C P, Lynn J W, Mukovskii Y M, et al. Charge Ordering and Polaron Formation in the Magnetoresistive Oxide La0.7Ca0.3MnO3. Phys. Rev. Lett., 2000, 85, 3954-3957.
[82] Zhang J, Dai P, Fernandez-Baca J A, et al. Jahn-Teller Phonon Anomaly and Dynamic Phase Fluctuations in La0.7Ca0.3MnO3. Phys. Rev. Lett. 2001, 86: 3823-3826.
[83] Kapusta C, Riedi P C, Kocemba W, et al. A 55Mn nuclear magnetic resonance study of mixed-valence manganites. J. Phys.:Condens. Matter,1999,11:4079-4086.
[84] Sheng L, Xing D Y, Sheng D N, et al. Theory of colossal magnetoresistance in R1-xAxMnO3. Phy. Rev. Lett., 1997, 79 (9) : 1710-1713.
[85] Wagner P, Gordon I, Trappeniers L, et al. Spin dependent hopping and colossal negative magnetoresistance in epitaxial Na0.52Sr0.48MnO3 films in fields up to 50 T. Phys. Rev. Lett., 1998, 81 (18) : 3980-3983.
[86] Roy M, Mitchell J F, Potashnik S J, et al. Field dependent specific-heat of rare earth manganites. J. Magn. Magn. Mater. 2000, 218 : 191-197.
[87] Yuan S L, Tu F, Yang Y P, et al. Phase separation and transport behavior in La0.5Ca0.5-xBaxMnO3. Phys. Status Solid (a) 2001, 185, 391-399.
[88] Wang X L, Dou S X, Liu H K, et al. Large low-field magnetoresistance over a wide temperature range induced by weak-link grain boundaries in La0.7Ca0.3MnO3. Appl. Phys. Lett., 1998, 73 (3) : 396-398.
[89] Hueso L E, Rivas J, Rivadulla F, et al. Tuning of colossal magnetoresistance via grain size change in LaCaMnO. J. Appl. Phys. 1999, 86 (7) : 3881-3884.
[90] Balcells L, Carrillo A E, Martínez B, et al. Enhanced field sensitivity close to percolation in magnetoresiative La2/3Sr1/3MnO3/CeO2 composites. Appl. Phys. Lett. 1999, 74 (26) : 4014-4016.
[91] Petrov D K, Krusin-Eibaum L, Sun J Z, et al. Enhanced magnetoresistance in sintered granular manganite/insulator systems. Appl. Phys. Lett. 1999, 75 (7) : 995-997.
[92] Huang Y H, Chen X, Wang Z M, et al. Enahnced magnetoresistance in granular La2/3Ca1/3MnO3/polymer composites. J. Appl. Phys., 2002, 91(10) : 7733-7735.
[93] Das D, Saha A, Russek S E, et al. Large magnetoresistance in (La1-xCaxMnO3)1-y: ZrO2 composites. J. Appl. Phys., 2003, 93 (10) : 8301-8303.
[94] Liu J M, Yuan G L, Sang H, et al. Low-field magnetoresistance in nanosizedLa0.7Sr0.3MnO3/Pr0.5Sr0.5MnO3 composites. Appl. Phys. Lett., 2001, 78 (8) : 1110-1112.
[95] Yan C H, Xu Z G, Zhu T, et al. A large low field colossal magnetoresistance in the La0.7Sr0.3MnO3 and CoFe2O4 combined system. J. Appl. Phys., 2000, 87 (9) : 5588-5590.
[96] Xia Z C, Yuan S L, Zhang G H, et al. Effect of low Fe3O4 doping in La0.67Ca0.33MnO3. J. Phys. D: Appl. Phys., 2003, 36 : 217-222.
[97] Yuan S L, Zhang G Q, Peng G, et al. Electrical transport and low-field magnetoresistance in the series of mixed polycrystals (1-m)La2/3Ca1/3MnO3 + mLa2/3Sr1/3MnO3. J. Phys.: Condens. Matter., 2001, 13 : 5691-5697.
[98] Hong C S, Kim W S, Hur N H. Wide colossal magnetoresistance around room temperature in La0.7Ca0.3MnO3/La0.7Sr0.3MnO3 composites. Solid State Commu., 2002, 121 : 657-660.
[99] Huang Y H, Yan C H, Luo F, et al. Large enhancement in room-temperature magnetoresistance and dramatic decrease in resisticity in La0.7Ca0.3MnO3-Ag composites. Appl. Phys. Lett., 2002, 81 (1) : 76-78.
[100] Tang T, Zhang S Y, Huang R S, et al. Giant magnetoresistance of bulk polycrystalline La0.833Na0.167MnO3 with Ag2O addition. J. Alloys Commp., 2003, 353 : 91-94.
[101] Yuan X B, Liu Y H, Huang B X, et al. Large enhancement of room temperature magnetoresistance in Ag-added La0.67(Ca0.65Ba0.35)0.33MnO3. Solid State Commu., 2005, 135 : 170-173.
[102] Hong K M, Giordano N. New effects in ferromagnetic nanostructures. J. Magn. Magn. Mater., 1995, 151 (3) : 396-402
[103] Ravelosona D, Cebollada A, Briones F, et al. Domain-wall scattering in epitaxial FePd ordered alloy films with perpendicular magnetic anisotropy. Phys. Rev. B, 1999, 59 (6) : 4322-4326.
[104] Kent A D, Rudiger U, Yu J, et al. Magnetoresistance, micromagnetism, and domainwall effects in epitaxial Fe and Co structures with stripe domains. J. Appl. Phys., 1999, 85 (8) : 5243-5248.
[105] Wolfman J, Haghiri-Gosnet A M, Raveau B, et al. Large domain wall magnetoresistance up to room temperature in La0.7Sr0.3MnO3 bridges with nanoconstrictions. J. Appl. Phys., 2001, 89 (11) : 6955-6957.
[106] Blasco J, Garcia J, de Teresa J M, et al. Structure, magnetic, and transport properties of the giant magnetoresistive perovskites La2/3Ca1/3Mn1-xAlxO3. Phys .Rev. B, 1997, 55: 8905-8910.
[107] Righi L, Gorria P, Gutierrez J, et al. Influence of Fe in giant magnetoresistance ratio and magnetic properties of La0.7Ca0.3Mn1-xFexO3 perovskite type compounds. J. Appl. Phys. 1997, 81 : 5767-5769.
[108] Pissas M, Kallias G, Devlin E, et al. M?ssbauer study of La0.75Ca0.25Mn0.98Fe0.02O3 compound. J. Appl. Phys. 1997, 81: 5770-5772.
[109] Cai J W, Wong C, Shen B, et al. Colossal magnetoresistance of spin-glass perovskite La0.7Ca0.3Mn0.9Fe0.1O3. Appl. Phys. Lett., 1997, 71 :1727-1729.
[110] Gayathri N, Raychaudhuri A K, Tiwary S K, et al. Electric transport, magnetism, and magnetoresistance in ferromagnetic oxides with mixed exchange interactions:A study of the La0.7Ca0.3Mn1-xCoxO3 system. Phys .Rev. B,1997, 56: 1345.
[111] Rubinstein M, Gillespie D J, Snyder J E, et al. Effects of Gd, Co, and Ni doping in La2/3Ca1/3MnO3: Resistivity, thermopower, and paramagnetic resonance. Phys .Rev. B,1997, 56: 5412-5423.
[112] Ghosh K, Ogale S B, Ramesh R, et al. Transition-element doping effects in La0.7Ca0.3MnO3. Phys. Rev. B, 1999, 59(1):533-537.
[113] Wu B M, Li B, Zhen W H, et al. Spin-cluster effect and lattice-deformation-induced Kondo effect, spin-glass freezing, and strong phonon scattering in La0.7Ca0.3Mn1–xCrxO3. J. Appl. Phys.,2005, 97(10):103908-103913.
[114] Hong C S, Hur N H, Choi Y N. Magnetic exchange interactions induced byCr-doping in perovskite manganites. Solid State Commum.,2005, 133(8):531-536.
[115] Roy S, Dubenko I S, Ignatov A Y, et al. Study of the colossal magnetoresistance properties of the compound La1-xSrxAyMn1-yO3 (A=Cr, Re). J. Phys.: Condens. Matter., 2000,12 (45): 9465-9479.
[116] Sun Y, Xu X, Zhang Y. Effects of Cr doping in La0.67Ca0.33MnO3: Magnetization, resistivity, and thermopower. Phys. Rev. B, 2001, 63(5):054404-054408.
[117] Sun Y, Tong W, Xu X J, et al. Possible double-exchange interaction between manganese and chromium in LaMn1-xCrxO3. Phys. Rev. B, 2001, 63(17):174438-174442.
[118] Morales L, Allub R, Alascio B, et al. Structural and magnetotransport properties of LaMn1–xCrxO3.00 (0≤x≤0.15): Evidence of Mn3+-O-Cr3+ double-exchange interaction. Phys. Rev. B,2005, 72(13):132413/1-4.
[119] Qu Z, Pi L, Tan S, et al. Interplay between Cr and Mn probed by comparing the magnetic properties of La1–xSrxMn0.98Cr0.02O3 and La1–ySryMn0.98Ga0.02O3. Phys. Rev. B, 2006, 73:184407-184412.
[120] Cabeza O, Long M, Severac C, et al. Magnetization and resistivity in chromium doped manganites. J. Phys.: Condens. Matter., 1999, 11(12):2569-2578.
[121] Kimura T, Kumai R, Okimoto Y, et al. Variation of charge-orbital correlation with Cr doping in manganites. Phys. Rev. B,2000, 62 (22) :15021-15025.
[122] Soltanian S, Wang X L, Liu H K, et al. Effects of Cr doping on the structure, charge ordering, transport and spin ordering state in Nd0.5Sr0.5Mn1-xCrxO3. Physica C, 2001, 364-365:343-346.
[123] Deisenhofer J, Paraskevopoulos M, von Nidda H-A K, et al. Interplay of superexchange and orbital degeneracy in Cr-doped LaMnO3. Phys. Rev. B,2002, 66 (5): 054414-054420.
[124] Yuan S L, Li Z Y, Zeng X Y, et al. Effect of Cu doping at the Mn site on the transport and magnetic behaviors of La0.7Ca0.3MnO3. Eur. Phys. J. B, 2001,20:177-181.
[125] Yuan S L, Li Z Y, Zhang G. Q, et al. Magnetic behavior in the Cu doped samples of La0.7Ca0.3Mn1-xCuxO3(0≤x≤0.2). Solid State Commun., 2001,117:661-666.
[126] Sergeenkov S A, Bougrine H, Ausloose M, et al. A sharp decrease of resistivity in La0.7Ca0.3Mn0.96Cu0.04O3. JETP Lett., 1999, 69:858-862.
[127] Tovstolytkin A I, Pogorilyi A N, Shypil E V, et al. An Abnormal effect of level doping on the magnetism and coductivity of La2/3Ca1/3MnO3-δ. Phys. Metal. Metallography. 2001, 91 : S214-S218.
[128] Steenbeck K, Eick T, Kirsch K, et al. Influence of a 36.8 degrees grain boundary on the magnetoresistance of La0.8Sr0.2MnO3-delta single crystal films. Appl. Phys. Lett., 1997, 71 (7) : 968-970.
[129] Cooke M D, Hatton H J, Wang L C, et al. Influence of interfaces on magnetostrictive granular films. Phys. Rev. B, 2002, 65 (17) : 174418-174424.
[130] Bides M, Balcells L, Fontcuberta J, et al. Surface-induced phase separation in manganites: A microscopic origin for powder magnetoresistance. Appl. Phys. Lett., 2003, 82 (6) : 928-930.
[131] Yuan S L, Peng G, Xia Z C, et. al., Cation Size and Strain Effects in La2/3(Ca1-x’Srx’-x’’Bax’’)1/3MnO3. Solid State Commun., 2002, 121:501-504.
[132] Salamon M B. Griffiths singularities and magnetoresistive manganites. Phys. Rev. B, 2003, 68:014411/1-8.
[133] Gu J Y, Bader S D, Zheng H, et al. Heat capacity of naturally layered SrO(La1–xSrxMnO3)2 single crystals. Phys. Rev. B, 2004,70:054418-054425.
[134] Shannon R D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides. Acta Cryst. A 32 :(1976) 751-766.
[135] Rozenberg E, Auslender M, Felner I, et al. Low-temperature resistivity minimum in ceramic manganites. J. Appl. Phys., 2000, 88 (5) : 2578-2582.
[136] Rao G H, Sun J R, Sun Y Z, et al. Magnetoresistance behaviour of La1-xCaxMnO3 compounds. J. Phys.: Condens. Mater.,1996, 8 (29):5393-5400.
[137] Sun J R, Rao G H, Shen B G, et al. Doping effects arising from Fe and Ge for Mn in La0.7Ca0.3MnO3. Appl. Phys. Lett., 1998, 73(20):2998-3000.
[138] Song H, Kim W, Kwon S J, et al. Magnetic and electronic properties of transition-metal-substituted perovskite manganites-La0.7Ca0.3Mn0.95X0.05O3 (X=Fe,Co,Ni). J. Appl. Phys., 2001, 89 (6):3398-3402.
[139] Cao D, Bridges F, Anderson M, et al. Local distortions in La0.7Ca0.3Mn1-bAbO3 (A=Ti and Ga) colossal magnetoresistance samples: Correlations with magnetization and evidence for cluster formation. Phys. Rev. B, 2001,64 (18) :184409/1-14.
[140] Qin H, Hu J, Chen J, et al. Room temperature magnetoresistance in La0.67Sr0.33Mn1?xAlxO3 manganites (x≤0.25). J. Magn. Magn. Mater., 2003, 263 (3): 249-252.
[141] Sugantha M, Singh R S, Rao C N R, et al. Effect of substitution of Mn3+ by other trivalent cations on the colossal magnetoresistance and related properties of the manganates : La0.7A0.3Mn1-xMxO3 (A=Ca, Sr, Pb; M=Al, Cr, Fe, Co). Mater. Res. Bull. 1998, 33 (7) :1129-1134.
[142] Kim M S, Yang J B, Cai Q, et al. Structure, magnetic, and transport properties of Ti-substituted La0.7Sr0.3MnO3. Phy. Rev. B, 2005, 71:014433/1-8.
[143] Feng J W, Ye C, Hwang L P. Ferromagnetic cluster behaviors and magnetoresistance in Ni-doped LaSrMnO3 systems. Appl. Phys. Lett. 1999, 75(11): 1592-1594.
[144] Hu J, Qin H, Chen J. Room temperature magnetoresistance in La0.67Sr0.33 Mn1-xCrxO3. Solid State Commum., 2002,124 :437-439.
[145] Kallel N, Dhahri J, Zemni S, et al. Effect of Cr doping in La0.7Sr0.3Mn1-x CrxO3 with 0≤x≤0.5. Phys. Stat. Sol. a, 2001, 184 (2) :319-325.
[146] Yuan S L, Zhang L J, Xia Z C, et al. Effect of sintering temperature on electronic transport and low-field colossal magnetoresistance in sol-gel prepared polycrystals of nominal La2/3Ca1/3Mn0.96Cu0.04O3. Phys. Rev. B, 2003, 68 (17) : 172408/1-4.
[147] Yuan S L, Tang J, Xia Z C, et al. A comparative study of low-fieldmagnetoresistance for La2/3Ca1/3Mn1-xCuxO3 (x=0% and 4%) synthesized at different temperatures. J. Phys. D: Appl. Phys., 2003, 36 : 1446-1450.
[148] Sun Y, Xu X J, Tong W, et al. Heat capacity of naturally layered SrO(La1–xSrxMnO3)2 single crystals. Appl. Phys. Lett. 2000, 77:(17) 2734-2736.
[2] Gary A. Prinz. Magnetoelectronics. Science, 1998, 282 (27) : 1660-1663.
[3] Wolf S A, Awschalom D D, Buhrman R A, et al. Spintronics: A spin-based electronics vision for the future. Science, 2001, 294 (16) : 1488-1495.
[4] Park J H, Vescovo E, Kim H J, et al. Direct evidence for a half-metallic ferromagnet. Nature, 1998, 392 (23) : 794-796.
[5] Hwang H Y, Cheong S W, Ong N P, et al. Spin-polarized intergrain tunneling in La2/3Sr1/3MnO3. Phys. Rev. Lett . 1996 , 77 (10) : 2041-2044.
[6] von Helmolt R, Wecker J, Holzapfel B, et al. Giant negative magnetoresistance in perovskite like La2/3Ba1/3MnO3 ferromagnetic films. Phys. Rev. Lett., 1993, 71 (14) : 2331-2333.
[7] Jin S, Tiefel T H, McCormack M, et al. Thousandfold change in resistivity in magnetoresistive La-Ca-Mn-O films. Science, 1994, 264 (5157) : 413-415.
[8] Booth C H, Bridges F, Kwei G H, et al. Direct relationship between magnetism and MnO6 distortions in La1-xCaxMnO3. Phys. Rev. Lett., 1998, 80 (4) : 853-856.
[9] Uhlenbruck S, Teipen R, Klingeler R,et al. Interplay between charge order, magnetism, and structure in La0.875Sr0.125MnO3. Phys. Rev. Lett., 1998, 82: 185-187.
[10] Li X W, Gupta A, Xiao G, et al. Low-field magnetoresistive properties of polycrystalline and epitaxial perovskite manganite films. Appl. Phys. Lett., 1997, 71 (8) : 1124-1126.
[11] Schiffer P, Ramirez A P, Bao W, et al. Low field magnetoresistance and the magnetic phase-diagram of La1-xCaxMnO3. Phys. Rev. Lett., 1995, 75 (18) : 3336-3339.
[12] Zhang N, Ding W P, Zhong W, et al. Tunnel-type giant magntoresistance in the granular perovskite La0.85Sr0.15MnO3. Phys. Rev. B, 1997, 56 (13) : 8138-8142.
[13] Gupta A, Gong G Q, Xiao G, et al. Grain-boundary effects on the magnetoresistance properties of perovskite manganite films. Phys. Rev. B, 1996, 54 (22) : R15629-R15632.
[14] Yakel H L. On the structure of some compounds of the perovskite type. Acta Crystallogr, 1955, 8 (7) : 394-398.
[15] Goodenough J B, Longon J M, Tabellen B L. New Series, GroupⅢ(4), Pt, a Springer, Berlin,1970.
[16] Goodenough J B. Colossal magnetoresistance in Ln1-xAxMnO3 perovskite. Aust. J. Phys., 1999, 52 (2) : 155-186.
[17] Goodenough J B. Electronic structure of CMR manganites. J. Appl. Phys., 1997, 81 (8) : 5330-5335.
[18] Haghiri-Gosnet A M, Renard J P, CMR manganites: physics, thin films and devices. J. Phys. D: Appl. Phys., 2003, 36 : R127-150.
[19] Millis A. J, Littlewood P B, Shraiman B I. Double exchange alone doesnot explain the resistivity of La1-xSrxMnO3. Phys. Rev. Lett., 1995, 74 (25) : 5144–5147.
[20] Goodenough J B. In magnetism and the chemical bond, Interscience, New York, 1963, Chap. 3.
[21] Argyriou D N, Mitchell J F, Patter C D, et al. Lattice effects and magnetic order in the canted ferromagnetic insulator La0.875Sr0.125MnO3. Phys. Rev. Lett., 1996, 76 (20) : 3826-3829.
[22] Pickett W E, Singh J. Electronic structure and half-metallic transport in the La1-xCaxMnO3 system. Phys. Rev. B, 1996, 53 (3) : 1146-1160.
[23] Cheong S W, Hwang H Y. Contribution to colossal magnetoresistance oxides. In: Tokura, Monographs in Condensed Matter Science Gordon & Breach, London 1999.
[24] Anderson P W, Hasegawa H. Considerations on double exchange. Phys. Rev., 1955, 100 (2) : 675-681.
[25] Jonker G H, Van Santen J H. Low temperature magnetoresistance and the magneticphase diagram of La1-xCaxMnO3. Physica, 1950, 16 (3) : 337-383.
[26] de Gennes P G. Effects of double exchange in magnetic crystals. Phys. Rev. 1960, 118 (1) : 141-154.
[27] Wu G R. Inoue M, Sasaki M, et al. Carrier generation/reombination processes and polaron effect in pervoskite manganite thin film. Physics B, 2000, 284 (2) : 1912-1913.
[28] Mott N F, Davis E A. Electronic Processes in Non Crystalline Material. Oxford: Oxford University Press, 1979, 52-56.
[29] Jia Y X, Lu L. Pr-doping of high-magnetoresistance perovskite Nd2/3Sr1/3MnO3. Solid State Communnication, 1995, 94 (11) : 917-921.
[30] Guo Z B, Zhang J R, Zhang N, et al. Electrical properties of La0.7-xPrxSr0.3MnO3 pervoskites. Appl. Phys. Lett., 1997, 70 (14) : 1897-1899.
[31] Gong G Q, Canedy C, Xiao G. Colossal magnetoresistance of 1000000 fold magnitude achieved in the antiferromagnetic phase of La1-xCaxMnO3, Appl. Phys. Lett., 1995, 67:1783-1785.
[32] Hwang H Y, Cheong S W, Ong N P, et al. Lattice effects on the magnetoresistance in doped LaMnO3. Phys. Rev. Lett., 1995, 75:914-919.
[33] Dagotto E, Hotta T, Moreo A. Colossal magnetoresistant materials: The key role of phase separation. Phys. Rep. 2001, 344 (1-3) : 1-153.
[34] Moreo A,Seiji Y, Elbio D. Phase separation secenario for manganese oxidex and related materials. Science, 1999, 283 (26) : 2034-2040.
[35] Wollan E O, Koehler W C. Neutron diffraction study of the magnetic properties of the series of perovskite-type compounds [(1-x) La, xCa]MnO3. Phys. Rev., 1955, 100 (2) : 545-563.
[36] Liu K, Wu X W, Ahn K H, et al. Charge ordering and magnetoresistance in Nd1-xCaxMnO3 due to reduced double exchange. Phys. Rev. B, 1996, 54:3007-3010
[37] Tokura Y, Tomioka Y. Origins of colossal magnetoresistance in perovskite-typemanganese oxides. J. Appl. Phys., 1996, 79:5288-5291.
[38] Gong G Q, Canedy C L, Xiao G. Colossal magnetoresistance in the antiferromagnetic La0.5Ca0.5MnO3 system. J. Appl. Phys. 1996, 79: 4538-4540.
[39] Radaelli P G, Cox D E, Marezio M, et al. Simultaneous structure, magnetic, and eletronictransitions in La1-xCaxMnO3 with x = 0.25 and 0.5. Phys. Rev. Lett., 1995, 75(24): 4488-4491.
[40] Balagurov A M, Pomjakushin V Yu, Sheptyakov D V, et al. Long-scale phase separation versus homogeneous magnetic state in (La1-yPry)0.7Ca0.3MnO3: A neutron diffraction study. Phys. Rev. B, 2001, 64(2):024420/1-10.
[41] Yuan S L, Liu J, Xia Z C, et al. Correction to the metal-insulator transition due to cation size and strain effect for colossal magnetoresistance perovskites. Chin. Phys. Lett, 2002, 19:1675-1678.
[42] F?th M, Freisem S, Menovsky A A, et al. Spatially inhomogeneous metal-insulator transition in doped manganites. Science, 1999, 285 (5433) :1540-1542.
[43] Rodriguez-Martinez L M, Attfield J P. Cation disorder and the metal-insulator transition temperature in manganese oxide perovskites . Phys. Rev. B, 1998, 58(5):2426-2431.
[44] Rodriguez-Martinez L M, Attfield J P. Disorder-induced orbital ordering in L0.7M0.3MnO3 perovskites. Phys. Rev. B, 2000, 63(2): 024424-024430.
[45] Meskine H, K?nig H, Satpathy S. Orbital ordering and exchange interaction in the manganites. Phys. Rev. B, 2001, 64(9): 094433/1-13.
[46] Zhou J S, Goodenough J B. Dynamic Jahn-Teller distortions and thermal conductivity in La1-xSrxMnO3 crystals. Phys. Rev .B, 2001, 64(2):024421-024424.
[47] Rivadulla F, López-Quintela M A, Mira J, et al. Jahn-Teller vibrational anisotropy determines the magnetic structure in orthomanganites. Phys. Rev .B, 1998, 64(5):052403-052407.
[48] Rodriguez-Martinez L M, Attfield J P. Cation disorder and size effects in magnetoresistive manganese oxide perovskites. Phys.Rev.B. 1996, 54: 15622-15625.
[49] Mathieu R, Akahoshi D, Asamitsu A, et al. Colossal magnetoresistance without phase separtation: disorder-induced spin glass state and nanometer scale orbital-charge correlation in half doped manganites. Phys.Rev.Lett., 2004, 93:227202-227206.
[50] Zener C. Interaction between the d-shell in the transition metal. II. ferromagnetic compounds of manganese with pervoskite structure. Phys. Rev. 1951, 82 : 403-405.
[51] Anderson P W, Hasegawa H. Considerations on double exchange. Phys. Rev., 1955, 100 (2) : 675-681.
[52] Searle C W, Wang S T. Magnetic properties in La0.69Pb0.31MnO3. J. Phys., 1970, 48 (17) : 2023-2031.
[53] Calderon M J, Verges J A , Brey L. Conductance as a function of temperature in the double-exchange model. Phys. Rev. B, 1999, 59(6): 4170-4175.
[54] Ishizaka S, Ishihara S. Temperature dependence of the resistivity in the double-exchange model. Phys. Rev. B, 1999, 59(13): 8375-8378.
[55] Snyder G J, Hiskes R, Dicarolis S, et al. Intrinsic electrical transport and magnetocproperties of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 MOCVD thin films and bulk material. Phys. Rev. B, 1996, 53 (21) : 14434-14444.
[56] Jaime M, Lin P, Salamon M B, et al. Low-temperature electrical transport and double exchange in La0.67(Pb,Ca)0.33MnO3. Phys. Rev. B, 1998, 58: R5901-5904.
[57] Alonso J L, Fernandez L A, Guinea F, et al. Discontinuous transitions in double-exchange materials. Phys. Rev. B, 2001, 63:064416/1-7.
[58] Millis A J, Shraiman B I, Mueller R. Dynamic Jahn-Teller Effect and Colossal Magnetoresistance in La1-xSrxMnO3. Phys. Rev. Lett.,1996, 77 :175-178.
[59] Millis A J, Mueller R, Shraiman B I. Fermi-liquid-to-polaron crossover. I. General results. Phys. Rev. B 1996 54: 5389-5393.
[60] Millis A J, Mueller R, Shraiman B I. Fermi-liquid-to-polaron crossover. II. Double exchange and the physics of colossal magnetoresistance. Phys. Rev. B, 1996, 54: 5405-5409.
[61] Coey J M D, Viret M, von Molnar S. Mixed-valence manganites. Adv. Phys. 1999, 48 (2) : 167-256.
[62] McCormack M, Jin S, Tiefel T H, et al. Very large magnetoresistance in perovskite-like La-Ca-Mn-O thin films. Appl. Phys. Lett., 1994, 64 (22) : 3045-3047.
[63] Jin S, Obryan H M, Tiefel T H, et al. Large magnetoresistance in ploycrystalline La-Ca-Mn-O, Appl. Phys. Lett., 1995, 66 (3) : 382-384.
[64] Tokura Y, Urushibara A, Moritomo Y, et al. Giant magnetotransport phenomena in filling-controlled kondo lattice system: La1-xSrxMnO3. J. Phys. Soc. Japan, 1994, 63 (11) : 3931-3938.
[65] Urushibara A, Moritomo Y, Arima T, et al. Insulator-metal transition and giant magnetoresistance in La1-xCaxMnO3. Phys. Rev. B, 1995, 51 (20) : 14103-14109.
[66] Fontcuberta J, Martnez B, Seffar A, et al. Colossal magnetoresistance of ferromagnetic manganites: structure tuning and mechanisms. Phys. Rev. Lett., 1996, 76 (7) : 1122-1125.
[67] O'Donnell J, Onellion M, Rzchowski M S, et al. magnetoresistance scalling in MBE-grown La0.7Ca0.3MnO3 thin films. Phys. Rev. B, 1996, 54 (10) : R6841-R6844.
[68] Tomioka Y, Asamitsu A, Tokura Y. Magnetotransport properties and magnetostructure phenomenon in single crystals of La0.7(Ca1-ySry)0.3MnO3. Phys. Rev. B, 2001 63 (2) : 024421/1-6.
[69] Yuan S L, Tang J, Xia Z C, et al. Low-field colossal constant magnetoresistance for wide temperature ranges in the sol-gel prepared La2/3Ca1/3Mn0.96Cu0.04O3. Solid State Comm., 2003, 127 : 743-747.
[70] Nunez-Regueiro J E, Kadin A M. Phenomenological Model for Giant Magnetoresistance in Lanthanum Manganite. Applied Physics Letters, 1996, 68 (19) : 2747 -2749.
[71] Coey J M D, Viret M, Ranno L. Electron localization in mixed-valence manganites. Phy. Rev. Lett., 1995, 75 (21) : 3910-3913.
[72] Viret M, Ranno L, Coey J M D. Magnetic localization in mixed-valence manganites. Physical Review B, 1997, 55 (13) : 8067-8070.
[73] Zhang S F. Electrical conductivity in ferromagnetic perovskita structures. J. Appl. Phys., 1996, 79 (8) : 4542- 4544.
[74] Millis A J. Lattice effects in magnetoresistive manganese perovskites. Nature, 1998, 392 (12) : 147-150.
[75] Mott N F. Conduction in non-crystalline materials, Oxford University Press, New York, 1993, 1-285.
[76] Ziese M, Srinitiwarawong C. Polaronic effects on the resistivity of manganite thin films. Phys. Rev. B,1998, 58 :11519-11525.
[77] Jaime M, Salamon M B, Rubinstein M, et al. High-temperature thermopower in La2/3Ca1/3MnO3 films: Evidence for polaronic transport. Phys. Rev. B,1996, 54:11914-11918.
[78] Palstra T T M, Ramirez A P, Cheong S W, et al. Transport mechanisms in doped LaMnO3: Evidence for polaron formation. Phys. Rev. B, 1997, 56 :5104-5107.
[79] Jaime M, Hardner H T, Salamon M B, et al. Hall-Effect Sign Anomaly and Small-Polaron Conduction in (La1-xGdx)0.67Ca0.33MnO3. Phys. Rev. Lett. 1997, 78: 951-954.
[80] Wang L, Yin J, Huang S, et al. Thermally activated drift mobility and small polaron conduction in La0.75Sr0.11Ca0.14MnO3 thin films investigated by the traveling wave method. Phys. Rev. B,1999, 60: R6976-6980.
[81] Adams C P, Lynn J W, Mukovskii Y M, et al. Charge Ordering and Polaron Formation in the Magnetoresistive Oxide La0.7Ca0.3MnO3. Phys. Rev. Lett., 2000, 85, 3954-3957.
[82] Zhang J, Dai P, Fernandez-Baca J A, et al. Jahn-Teller Phonon Anomaly and Dynamic Phase Fluctuations in La0.7Ca0.3MnO3. Phys. Rev. Lett. 2001, 86: 3823-3826.
[83] Kapusta C, Riedi P C, Kocemba W, et al. A 55Mn nuclear magnetic resonance study of mixed-valence manganites. J. Phys.:Condens. Matter,1999,11:4079-4086.
[84] Sheng L, Xing D Y, Sheng D N, et al. Theory of colossal magnetoresistance in R1-xAxMnO3. Phy. Rev. Lett., 1997, 79 (9) : 1710-1713.
[85] Wagner P, Gordon I, Trappeniers L, et al. Spin dependent hopping and colossal negative magnetoresistance in epitaxial Na0.52Sr0.48MnO3 films in fields up to 50 T. Phys. Rev. Lett., 1998, 81 (18) : 3980-3983.
[86] Roy M, Mitchell J F, Potashnik S J, et al. Field dependent specific-heat of rare earth manganites. J. Magn. Magn. Mater. 2000, 218 : 191-197.
[87] Yuan S L, Tu F, Yang Y P, et al. Phase separation and transport behavior in La0.5Ca0.5-xBaxMnO3. Phys. Status Solid (a) 2001, 185, 391-399.
[88] Wang X L, Dou S X, Liu H K, et al. Large low-field magnetoresistance over a wide temperature range induced by weak-link grain boundaries in La0.7Ca0.3MnO3. Appl. Phys. Lett., 1998, 73 (3) : 396-398.
[89] Hueso L E, Rivas J, Rivadulla F, et al. Tuning of colossal magnetoresistance via grain size change in LaCaMnO. J. Appl. Phys. 1999, 86 (7) : 3881-3884.
[90] Balcells L, Carrillo A E, Martínez B, et al. Enhanced field sensitivity close to percolation in magnetoresiative La2/3Sr1/3MnO3/CeO2 composites. Appl. Phys. Lett. 1999, 74 (26) : 4014-4016.
[91] Petrov D K, Krusin-Eibaum L, Sun J Z, et al. Enhanced magnetoresistance in sintered granular manganite/insulator systems. Appl. Phys. Lett. 1999, 75 (7) : 995-997.
[92] Huang Y H, Chen X, Wang Z M, et al. Enahnced magnetoresistance in granular La2/3Ca1/3MnO3/polymer composites. J. Appl. Phys., 2002, 91(10) : 7733-7735.
[93] Das D, Saha A, Russek S E, et al. Large magnetoresistance in (La1-xCaxMnO3)1-y: ZrO2 composites. J. Appl. Phys., 2003, 93 (10) : 8301-8303.
[94] Liu J M, Yuan G L, Sang H, et al. Low-field magnetoresistance in nanosizedLa0.7Sr0.3MnO3/Pr0.5Sr0.5MnO3 composites. Appl. Phys. Lett., 2001, 78 (8) : 1110-1112.
[95] Yan C H, Xu Z G, Zhu T, et al. A large low field colossal magnetoresistance in the La0.7Sr0.3MnO3 and CoFe2O4 combined system. J. Appl. Phys., 2000, 87 (9) : 5588-5590.
[96] Xia Z C, Yuan S L, Zhang G H, et al. Effect of low Fe3O4 doping in La0.67Ca0.33MnO3. J. Phys. D: Appl. Phys., 2003, 36 : 217-222.
[97] Yuan S L, Zhang G Q, Peng G, et al. Electrical transport and low-field magnetoresistance in the series of mixed polycrystals (1-m)La2/3Ca1/3MnO3 + mLa2/3Sr1/3MnO3. J. Phys.: Condens. Matter., 2001, 13 : 5691-5697.
[98] Hong C S, Kim W S, Hur N H. Wide colossal magnetoresistance around room temperature in La0.7Ca0.3MnO3/La0.7Sr0.3MnO3 composites. Solid State Commu., 2002, 121 : 657-660.
[99] Huang Y H, Yan C H, Luo F, et al. Large enhancement in room-temperature magnetoresistance and dramatic decrease in resisticity in La0.7Ca0.3MnO3-Ag composites. Appl. Phys. Lett., 2002, 81 (1) : 76-78.
[100] Tang T, Zhang S Y, Huang R S, et al. Giant magnetoresistance of bulk polycrystalline La0.833Na0.167MnO3 with Ag2O addition. J. Alloys Commp., 2003, 353 : 91-94.
[101] Yuan X B, Liu Y H, Huang B X, et al. Large enhancement of room temperature magnetoresistance in Ag-added La0.67(Ca0.65Ba0.35)0.33MnO3. Solid State Commu., 2005, 135 : 170-173.
[102] Hong K M, Giordano N. New effects in ferromagnetic nanostructures. J. Magn. Magn. Mater., 1995, 151 (3) : 396-402
[103] Ravelosona D, Cebollada A, Briones F, et al. Domain-wall scattering in epitaxial FePd ordered alloy films with perpendicular magnetic anisotropy. Phys. Rev. B, 1999, 59 (6) : 4322-4326.
[104] Kent A D, Rudiger U, Yu J, et al. Magnetoresistance, micromagnetism, and domainwall effects in epitaxial Fe and Co structures with stripe domains. J. Appl. Phys., 1999, 85 (8) : 5243-5248.
[105] Wolfman J, Haghiri-Gosnet A M, Raveau B, et al. Large domain wall magnetoresistance up to room temperature in La0.7Sr0.3MnO3 bridges with nanoconstrictions. J. Appl. Phys., 2001, 89 (11) : 6955-6957.
[106] Blasco J, Garcia J, de Teresa J M, et al. Structure, magnetic, and transport properties of the giant magnetoresistive perovskites La2/3Ca1/3Mn1-xAlxO3. Phys .Rev. B, 1997, 55: 8905-8910.
[107] Righi L, Gorria P, Gutierrez J, et al. Influence of Fe in giant magnetoresistance ratio and magnetic properties of La0.7Ca0.3Mn1-xFexO3 perovskite type compounds. J. Appl. Phys. 1997, 81 : 5767-5769.
[108] Pissas M, Kallias G, Devlin E, et al. M?ssbauer study of La0.75Ca0.25Mn0.98Fe0.02O3 compound. J. Appl. Phys. 1997, 81: 5770-5772.
[109] Cai J W, Wong C, Shen B, et al. Colossal magnetoresistance of spin-glass perovskite La0.7Ca0.3Mn0.9Fe0.1O3. Appl. Phys. Lett., 1997, 71 :1727-1729.
[110] Gayathri N, Raychaudhuri A K, Tiwary S K, et al. Electric transport, magnetism, and magnetoresistance in ferromagnetic oxides with mixed exchange interactions:A study of the La0.7Ca0.3Mn1-xCoxO3 system. Phys .Rev. B,1997, 56: 1345.
[111] Rubinstein M, Gillespie D J, Snyder J E, et al. Effects of Gd, Co, and Ni doping in La2/3Ca1/3MnO3: Resistivity, thermopower, and paramagnetic resonance. Phys .Rev. B,1997, 56: 5412-5423.
[112] Ghosh K, Ogale S B, Ramesh R, et al. Transition-element doping effects in La0.7Ca0.3MnO3. Phys. Rev. B, 1999, 59(1):533-537.
[113] Wu B M, Li B, Zhen W H, et al. Spin-cluster effect and lattice-deformation-induced Kondo effect, spin-glass freezing, and strong phonon scattering in La0.7Ca0.3Mn1–xCrxO3. J. Appl. Phys.,2005, 97(10):103908-103913.
[114] Hong C S, Hur N H, Choi Y N. Magnetic exchange interactions induced byCr-doping in perovskite manganites. Solid State Commum.,2005, 133(8):531-536.
[115] Roy S, Dubenko I S, Ignatov A Y, et al. Study of the colossal magnetoresistance properties of the compound La1-xSrxAyMn1-yO3 (A=Cr, Re). J. Phys.: Condens. Matter., 2000,12 (45): 9465-9479.
[116] Sun Y, Xu X, Zhang Y. Effects of Cr doping in La0.67Ca0.33MnO3: Magnetization, resistivity, and thermopower. Phys. Rev. B, 2001, 63(5):054404-054408.
[117] Sun Y, Tong W, Xu X J, et al. Possible double-exchange interaction between manganese and chromium in LaMn1-xCrxO3. Phys. Rev. B, 2001, 63(17):174438-174442.
[118] Morales L, Allub R, Alascio B, et al. Structural and magnetotransport properties of LaMn1–xCrxO3.00 (0≤x≤0.15): Evidence of Mn3+-O-Cr3+ double-exchange interaction. Phys. Rev. B,2005, 72(13):132413/1-4.
[119] Qu Z, Pi L, Tan S, et al. Interplay between Cr and Mn probed by comparing the magnetic properties of La1–xSrxMn0.98Cr0.02O3 and La1–ySryMn0.98Ga0.02O3. Phys. Rev. B, 2006, 73:184407-184412.
[120] Cabeza O, Long M, Severac C, et al. Magnetization and resistivity in chromium doped manganites. J. Phys.: Condens. Matter., 1999, 11(12):2569-2578.
[121] Kimura T, Kumai R, Okimoto Y, et al. Variation of charge-orbital correlation with Cr doping in manganites. Phys. Rev. B,2000, 62 (22) :15021-15025.
[122] Soltanian S, Wang X L, Liu H K, et al. Effects of Cr doping on the structure, charge ordering, transport and spin ordering state in Nd0.5Sr0.5Mn1-xCrxO3. Physica C, 2001, 364-365:343-346.
[123] Deisenhofer J, Paraskevopoulos M, von Nidda H-A K, et al. Interplay of superexchange and orbital degeneracy in Cr-doped LaMnO3. Phys. Rev. B,2002, 66 (5): 054414-054420.
[124] Yuan S L, Li Z Y, Zeng X Y, et al. Effect of Cu doping at the Mn site on the transport and magnetic behaviors of La0.7Ca0.3MnO3. Eur. Phys. J. B, 2001,20:177-181.
[125] Yuan S L, Li Z Y, Zhang G. Q, et al. Magnetic behavior in the Cu doped samples of La0.7Ca0.3Mn1-xCuxO3(0≤x≤0.2). Solid State Commun., 2001,117:661-666.
[126] Sergeenkov S A, Bougrine H, Ausloose M, et al. A sharp decrease of resistivity in La0.7Ca0.3Mn0.96Cu0.04O3. JETP Lett., 1999, 69:858-862.
[127] Tovstolytkin A I, Pogorilyi A N, Shypil E V, et al. An Abnormal effect of level doping on the magnetism and coductivity of La2/3Ca1/3MnO3-δ. Phys. Metal. Metallography. 2001, 91 : S214-S218.
[128] Steenbeck K, Eick T, Kirsch K, et al. Influence of a 36.8 degrees grain boundary on the magnetoresistance of La0.8Sr0.2MnO3-delta single crystal films. Appl. Phys. Lett., 1997, 71 (7) : 968-970.
[129] Cooke M D, Hatton H J, Wang L C, et al. Influence of interfaces on magnetostrictive granular films. Phys. Rev. B, 2002, 65 (17) : 174418-174424.
[130] Bides M, Balcells L, Fontcuberta J, et al. Surface-induced phase separation in manganites: A microscopic origin for powder magnetoresistance. Appl. Phys. Lett., 2003, 82 (6) : 928-930.
[131] Yuan S L, Peng G, Xia Z C, et. al., Cation Size and Strain Effects in La2/3(Ca1-x’Srx’-x’’Bax’’)1/3MnO3. Solid State Commun., 2002, 121:501-504.
[132] Salamon M B. Griffiths singularities and magnetoresistive manganites. Phys. Rev. B, 2003, 68:014411/1-8.
[133] Gu J Y, Bader S D, Zheng H, et al. Heat capacity of naturally layered SrO(La1–xSrxMnO3)2 single crystals. Phys. Rev. B, 2004,70:054418-054425.
[134] Shannon R D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides. Acta Cryst. A 32 :(1976) 751-766.
[135] Rozenberg E, Auslender M, Felner I, et al. Low-temperature resistivity minimum in ceramic manganites. J. Appl. Phys., 2000, 88 (5) : 2578-2582.
[136] Rao G H, Sun J R, Sun Y Z, et al. Magnetoresistance behaviour of La1-xCaxMnO3 compounds. J. Phys.: Condens. Mater.,1996, 8 (29):5393-5400.
[137] Sun J R, Rao G H, Shen B G, et al. Doping effects arising from Fe and Ge for Mn in La0.7Ca0.3MnO3. Appl. Phys. Lett., 1998, 73(20):2998-3000.
[138] Song H, Kim W, Kwon S J, et al. Magnetic and electronic properties of transition-metal-substituted perovskite manganites-La0.7Ca0.3Mn0.95X0.05O3 (X=Fe,Co,Ni). J. Appl. Phys., 2001, 89 (6):3398-3402.
[139] Cao D, Bridges F, Anderson M, et al. Local distortions in La0.7Ca0.3Mn1-bAbO3 (A=Ti and Ga) colossal magnetoresistance samples: Correlations with magnetization and evidence for cluster formation. Phys. Rev. B, 2001,64 (18) :184409/1-14.
[140] Qin H, Hu J, Chen J, et al. Room temperature magnetoresistance in La0.67Sr0.33Mn1?xAlxO3 manganites (x≤0.25). J. Magn. Magn. Mater., 2003, 263 (3): 249-252.
[141] Sugantha M, Singh R S, Rao C N R, et al. Effect of substitution of Mn3+ by other trivalent cations on the colossal magnetoresistance and related properties of the manganates : La0.7A0.3Mn1-xMxO3 (A=Ca, Sr, Pb; M=Al, Cr, Fe, Co). Mater. Res. Bull. 1998, 33 (7) :1129-1134.
[142] Kim M S, Yang J B, Cai Q, et al. Structure, magnetic, and transport properties of Ti-substituted La0.7Sr0.3MnO3. Phy. Rev. B, 2005, 71:014433/1-8.
[143] Feng J W, Ye C, Hwang L P. Ferromagnetic cluster behaviors and magnetoresistance in Ni-doped LaSrMnO3 systems. Appl. Phys. Lett. 1999, 75(11): 1592-1594.
[144] Hu J, Qin H, Chen J. Room temperature magnetoresistance in La0.67Sr0.33 Mn1-xCrxO3. Solid State Commum., 2002,124 :437-439.
[145] Kallel N, Dhahri J, Zemni S, et al. Effect of Cr doping in La0.7Sr0.3Mn1-x CrxO3 with 0≤x≤0.5. Phys. Stat. Sol. a, 2001, 184 (2) :319-325.
[146] Yuan S L, Zhang L J, Xia Z C, et al. Effect of sintering temperature on electronic transport and low-field colossal magnetoresistance in sol-gel prepared polycrystals of nominal La2/3Ca1/3Mn0.96Cu0.04O3. Phys. Rev. B, 2003, 68 (17) : 172408/1-4.
[147] Yuan S L, Tang J, Xia Z C, et al. A comparative study of low-fieldmagnetoresistance for La2/3Ca1/3Mn1-xCuxO3 (x=0% and 4%) synthesized at different temperatures. J. Phys. D: Appl. Phys., 2003, 36 : 1446-1450.
[148] Sun Y, Xu X J, Tong W, et al. Heat capacity of naturally layered SrO(La1–xSrxMnO3)2 single crystals. Appl. Phys. Lett. 2000, 77:(17) 2734-2736.