摘要
随着科学技术特别是现代信息技术的迅飞猛进发展,社会信息化的进程日新月异,人们对电子元器件的小型化/微型化以及实现多功能化的要求越加迫切,因此使得人们在对集多种物理效应于一体的多功能材料的研究上显示出更多的关注和兴趣。而多铁性材料就是这样一类能够同时呈现出两种或两种以上铁性(如铁电性、铁磁性、铁弹性以及铁旋性)的多功能磁电材料。更为值得关注的是,在多铁性材料有可能实现铁磁性和铁电性之间的相互调控,也就是说能够在外加电场下比不仅使材料具有铁电极化性质,还能够诱导激发磁化,同样在外加磁场也能够诱导材料的铁电极化性质。
多铁性材料以及铁电性与铁磁性之间的耦合,包含着丰富的物理内容,它涉及到自旋与晶格或声子之间的耦合、铁磁与反铁磁耦合以及磁光耦合等,因此,在研究多铁材料中,可以通过外部物理场(磁场、温度场、电场以及电磁场)实施对多铁材料的调控,这就为铁电/铁磁性的互相耦合提供了依据。正是由于多铁材料具有以上丰富的物理研究内容,使得成为当前热门研究领域。
本文以BiFeO3多铁材料为基础,研究了掺杂改性以及与铁电材料(Bi0.5Na0.5TiO3和Bi4Ti3O12)形成固溶体,主要研究内容如下：
(1)我们采用硝酸盐-柠檬酸法制备了(1-x)BiFeO3-xBi0.5Na0.5TiO3系列固溶体陶瓷样品,以及Ba掺杂x=0.3的样品。详细研究了固溶体陶瓷样品微观结构、形貌、铁电性、磁性以及光学性能。研究结果显示,Bi0.5Na0.5TiO3含量逐渐增加引起晶体结构由菱方逐渐向膺立方相转变,转变临界点在x=0.4处。和纯相BiFeO3材料相比,x=0.3的样品具有较好的多铁性,获得的剩余极化强度和饱和磁化强度分别为Pr=1.49μC/cm2和Ms=0.51emu/g.更为重要的是,顺磁到铁磁相的转变在此固溶体材料中也被观察到,居里温度也能够通过变化Bi0.5Na0.5TiO3的含量进行调节。这里观察到的铁磁有序主要是由于在化学有序区域内可能存在Fe3+-O-Ti-O-Fe3+的长程超交换作用。同时,Ba掺杂0.7BiFeO3-0.3Bi0.5Na0.5TiO3固溶体,磁滞回线测量表明磁性能获得了极大的增强。在x=0.2固溶体中,磁滞回线测量获得了最大剩余磁化,数值为0.55emu/g。Ba的掺杂还提高了陶瓷粉末的禁带宽度。
(2)我们详细研究了固溶体的动态磁性能、介电性能以及微波吸收性能。结果显示,所有样品的磁性能、介电性能随频率的变化趋势相同。随着含量x的增加,Bi0.5Na0.5TiO3掺杂固溶样品的反射损耗逐渐的减小,也就是说,微波吸收性能在减弱,小于-10dB的带宽也在不断的减小。在2-18GHz,x=O.1和0.2的样品相对来说具有较好的吸收特性。但是由于复介电常数和复磁导率存在巨大的差异性,导致了微波吸收性能较差。因此,有必要进一步提高阻抗匹配特性。
(3)采用硝酸盐-柠檬酸法制备Bi0.8Ba0.2Fe1-xNbxO3系列陶瓷样品,研究了共掺杂材料的铁磁性、铁电性、介-频/介-N性质以及室温磁电耦合性质。Nb掺杂增强了材料的铁电和铁磁性质。结果显示,获得磁电增强的Bi0.8Ba0.2Fe0.975Nb0.025O3陶瓷的剩余极化强度和矫顽场(Mr和Pr)分别为3.69emu/g和1.34μC/cm2。从介电随频率测量中看到,Nb掺杂减小了低频频散和介电损耗。通过介温曲线测量发现,在反铁磁转变温度出现了介电反常。Nb的掺杂有助于减小介电损耗,尤其在低频范围内。同时,x=-0.015和0.025样品处于磁场磁化后,测量得到的剩余极化强度都获得了增强,这样就间接证明了室温磁电耦合的存在。
(4)采用固相法制备了Bi5Ti3FeO15陶瓷样品,研究该材料的微观结构、介电性质随温度的变化关系、交流电导特性、铁电性、铁磁性以及光吸收特性。结果显示,Bi5Ti3FeO15陶瓷样品具有层状钙钛矿结构,颗粒尺寸在2-5μm范围内。介温测量显示在该材料中存在两个介电反常,分别在1007和1090K,预示着也有两种相变的存在,但是在tanδ-T曲线内并没有观察到峰的出现。同时,计算出在476-639K,652-966K和980-1095K内的激活能分别为0.156,0.262和0.707eV。通过电滞回线测量得到的剩余极化强度(2Pr)和矫顽场(2Ec)分别为6.08μC/cm2和59kV/cm。磁性测量表明Bi5Ti3FeO15陶瓷在室温下具有弱的铁磁性,我们对磁性的起源也作了分析。通过紫外-可见光吸收光谱测量,计算拟合得到的禁带宽度为2.03eV。
(5)采用硝酸盐-柠檬酸法制备了La掺杂Bi9Ti3Fe5O27系列陶瓷样品,研究了材料的微观结构、介电性质随温度的变化关系、铁电性、铁磁性以及磁电耦合性质。研究表明随着La3+离子含量的增加,样品的颗粒尺寸逐渐减小,材料的磁性也得到逐步的增强。同时样品的铁电-顺电相变温度逐渐的移向低温区。对于Bi6La3Ti3Fe5O27样品,结构个高分辨电镜分析表明该合成直径为2μm厚度为160-170nm的片状结构材料,这是由于材料在(001)面加速生长造成的。La掺杂已经显示能够很好的实现室温铁电性／铁磁性的共存,因此也预示稀土掺杂是提高反铁磁Bi9Ti3Fe5O27多铁性质的一种较好方式。在Bi6La3Ti3Fe5O27陶瓷中,在500-590和600-650K温区内观察到两种介电反常现象,较高温度的反常对应着铁电-顺电相变。惊喜的是,通过测量磁化前后的电滞回线以及外加磁场下的介电常数发现样品在室温下存在着电荷与自旋间的磁电耦合效应。研究发现,磁介电响应随着外加磁场的增大而增大,而且对频率具有非线性依赖关系。
Multiferroic materials, which combine the properties of ferromagnetism, ferroelectricity, or ferroelasticity, have attracted more and more attention due to their possible application toward storage materials and intriguing fundamental physics. Besides, coupling between magnetic and electric order parameters can give rise to the magnetoelectric effect, in which the magnetization can be exhibited under an external electric field and vice versa. BiFeO3is one such material which shows a lot of potential for research. This material is antiferromagnetic and ferroelectric having an antiferromagnetic Neel temperature (TN) of643K and a ferroelectric Curie temperature (Tc) of1103K. It has been shown to possess a rhombohedrally distorted perovskite structure with space group R3c at room temperature. In addition, BiFeO3shows G-type antiferromagnetic order where the Fe magnetic moments are coupled ferromagnetically within the (111) planes and antiferromagnetically between adjacent planes. When the ferromagnetically ordered magnetic moments are aligned parallel to the (111) planes, the symmetry allows canting of the antiferromagnetic sublattices, which gives rise to macroscopic magnetization as a whole This spiral spin structure can be suppressed by doping. However, as for BiFeO3bulk ceramics, research work is still being hindered by the easy formation of second phases during synthesis and the low electrical resistivity of samples. Recent work mainly has focused on (a) binary or ternary solid solution of BiFeO3with other ABO3perovskite materials (such as BaTiO3, Bi0.5Na0.5TiO3) and (b) A/B sites co-doping.
This paper based on BiFeO3multiferroic materials, and research on doping modification, as well as the formation of solid solution of with ferroelectric material (Bio5Na0.5TiO3of Bi4TisO12). We have done the following work:
(1) We prepared the (1-x)BiFe03-xBio.5Nao.5Ti03ceramics and Ba doped0.7BiFe03-0.3Bio.5Nao.5Ti03, and investigated the microstructure, ferromagnetic, ferroelectric properties in detail. The results show that increasing Bi0.5Na0.5TiO3content induce a gradual phase transformation from rhombohedral to pseudocubic structure near x=0.4. Compared with pure BiFeO3, superior multiferroic properties are obtained for x=0.3with remnant polarization Pr=1.49μC/cm2and saturated magnetization Ms=0.51emu/g. Importantly, the paramagnetic to ferromagnetic transition is observed for the solutions, and the Curie temperature (Tc) can be tuned by varying the content of Bi0.5Na0.5TiO3.This observed ferromagnetic ordering is discussed in terms of the possible existence of the long-range superexchange interaction of Fe3+-Ti-O-Fe3+in the chemically ordered regions. At the same time, significant magnetic enhancement was observed for0.7BiFe03-0.3Bio.5Nao.5Ti03with Ba doping. Ferromagnetic hysteresis loops revealed the maximum remanent magnetization of0.55emu/g for0.7B1-xBxF-0.3BNT of x=0.2. The effect of introducing La is shown to increase the optical band gap for doped sample0.7B1-xBxF-0.3BNT.
(2) We investigated the dynamic magnetic, dielectric and microwave absorbing properties in detail. The results show that all samples have the similar behaviors. With the increasing of the content x, the reflectivity of Bi0.5Na0.5TiO3doped samples decrease, that is to say, the microwave absorption properties decrease, and the bandwidths of lower than-lOdB was also decreased. At2-18GHz, x=0.1and0.2samples have relatively better absorption properties. But because of the great differences between complex dielectric constant and complex permeability, results in the bad microwave absorption properties, thus impedence matching need to further improve。
(3) We prepared the Bi0.8Ba0.2Fe1-xNbx03ceramics and investigated the ferromagnetic, ferroelectric, dielectric constant versus temperature/dielectric constant versus frequency and room temperature magnetoelectric coupling properties. Substitution with Nb also improved the ferroelectric polarization. As a result, enhanced multiferroic properties of Bi0.8Ba0.2Fe0.975Nbo.o2503ceramics with remanent magnetization and polarization (Mr and Pr) of3.69emu/g and1.34μC/cm, respectively, were obtained. The reduction of low-frequency dispersion in permittivity and loss due to Nb substitution in was observed in its dielectric response curve. An anomaly in the dielectric constant was observed in the vicinity of the antiferromagnetic transition temperature. Nb Substitution was found to be helpful to reduce loss, especially at lower frequencies. In addition, an enhancement in remanent polarization after poling the samples with x=0.015and0.025in the dc magnetic field was evidence of magnetoelectric coupling at room temperature.
(4) We prepared the Bi5Ti3FeO15ceramics and investigated the microstrcture, dielectric constant versus temperature, ac conductivity, ferroelectric, ferromagnetic, and optical performances. The results show that polycrystalline Bi5Ti3FeO15ceramics of layered perovskite phase, having particle size of2-5μm, Two obvious dielectric anomalies around1007and1090K were exhibited by this material, indicating that there are two phase transitions. While no peak was found in the tanδ-T curve. In addition, the conduction loss activation energies calculated at476-639K,652-966K, and980-1095K are0.156,0.262, and0.707eV, respectively. Polarization versus electric field hysteresis loops associated with2Pr of6.08μC/cm2and2EC of59kV/cm were obtained. The result of magnetic measurement indicated the weak ferromagnetic order of Bi5Ti3FeO15ceramics at room temperature, we also analyzed the origin of the obtained magnetism. An energy band gap of2.03eV was determined from the UV-vis diffuse absorption spectrum.
(5) We prepared the La doped Bi9Ti3Fe5O27ceramics and investigated the materials' microstrcture, dielectric constant versus temperature, ferroelectricity, ferromagnetism, and magnetoelectric coupling property. Results reveal that increasing the La3+ions content, the particles of the materials will be decreased, and the ferromagnetism will be enhanced. Meanwhile, the transition temperature from the ferroelectric structure to the paraelectric structure will shift toward lower temperatures. As for Bi6La3Ti3FesO27, the structural and HRTEM analysis indicates that the formation of BLTF with plate-like morphology with about2μm. in diameter and160-170nm in thickness result from the accelerating growth of (001) crystalline planes. La substitution has been shown to effectively induce the coexistence of ferroelectricity and ferromagnetism at room temperature, thus indicating a promising way for improving multiferroic properties of antiferromagnetic Bi9Ti3Fe5O27. Two dielectric relaxations were observed in the temperature ranges of500-590and600-650K in BLTF ceramics, and the higher temperature dielectric relaxation is related to the ferroelectric phase transition. Surprisingly, the magnetoelectric coupling between charge and spin ordering at room temperature was demonstrated by measuring the effect of magnetic poling on ferroelectric hysteresis loop and the change in dielectric constant with the external magnetic field. It was found that the magnetodielectric response increased with the increase of magnetic field and showed a frequency dependent nonlinear response.
引文
[1]迟振华,靳常青,单相磁屯多铁性体研究进展物理学进展,2007,27：225-238
[2]Eerenstein W, Mathur N D, Scott J F, Multiferroic and magnetoelectric materials Nature,2006,442:759-765
[3]Dzyaloshinskii I E.The Magnetoelectric Effect in Antiferromagnetic Materials. Soviet Physics JETP,1960,10:628-629
[4]Ast rov D N, The magnetoelectric effect in antiferromagnetics, Sov Phys JETP 1960, 11:708
[5]Tokura Y, Multiferroics toward strong coupling between magnetization and polarization in a solid, J Magn Magn Mater 2007,310:1145-1150
[6]Lorenz B, Litvinchuk A P, Gospodinov M M, et al, Field—Induced Reentrant Novel Phase and a Ferroelectric—Magnetic Order Coupling in HoMnO3, Phys Rev Lett 2004,92:087204
[7]J. Valasek, Piezo-electric and allied phenomena in Rochelle salt, Phys Rev.1921, 17:475-481
[8]钟维烈,《铁电物理学》,科学出版社,1998
[9]V. L. Ginzburg, Phase transitions of the second kind and the microscopic theory of seignettoelectricity, Sov. Phys. Solid State 1960,2:2031-43.
[10]E. Ascher, Permutation representations, epikernels and phase transitions, J. Phys. C:Solid State Phys.1977,10:1365-1377
[11]A. D. Rae, J. G Thompson and R. L. Withers, Structure refinement of commensurately modulated bismuth strontium tantalite SrBi2Ta2O9, Acta Crystallogr. Sect. B:Struct. Sci.1992,48:418-428
[12]冯端,金国钧,凝聚态物理学,2003
[13]刘朝霞.单相多铁性材料BIFeO3的溶胶凝胶法制备与表征,河南：河南大学,2007
[14]Keitsiro Aizu, Possible Species of Ferromagnetic, Ferroelectric, and Ferroelastic Crystals, Phys.Rev.B.1970,2:754-772
[15]H.Schmid, Multi-ferroicmagnetoelectrics, Ferroelectrics 1994,162:317-338
[16]X. Y. Zhang, C. W. Lai, X. Zhao, D. Y. Wang, J. Y. Dai. Synthesis and ferroelectric properties of multiferroic BiFeO3 nanotube arrays, Applied Physics Letters.2005, 87:143102
[17]Lebeugle D, Colson D, Forget A, et al. Very large spontaneous electric polarization in BiFeO3 single crystals at room temperature and its evolution under cycling fields, Appl. Phys. Lett.2007,91:022907
[18]Joonghoe Dho, Xiaoding Qi, Hyunho Kim, et al. Large Electric Polarization and Exchange Bias in Multiferroic BiFeO3, Adv Mater 2006,18:1445-1448
[19]苗兰冬,宋功保,王美丽,李建,浅谈多铁性材料,中国陶瓷工业2006,13：39-43
[20]Mizokawa T, Khomskii D I, Sawatzky G A, Interplay between orbital ordering and latticedistortions in LaMnO3, YVO3, and YTiO3, Phys. Rev. B 1999,60:7309-7313
[21]Y. Murakami, J. P. Hill, D. Gibbs, M. Blume, I. Koyama, M. Tanaka, H. Kawata, et al. Resonant X^ray scattering from orbital ordering in LaMnO3, Physical Review Letters 1998,81:582-585
[22]Y. H. Huang, H. Fjellvag, M. Karppinen, B. C. Hauback, H. Yamauchi, J.B.Goodenoug, Crystal and Magnetic Structure of the Orthothombic Pervskite YbMnO3, Chemistry of Materials 2006,18:2130-213
[23]Jun Y. K., Moon W. T., Chang C. M., Kim H. S., et al. Effects of Nb-doping on electric and magnetic properties in multiferroic BiFeO3 ceramics, Solid State Commun.2005,135:133-137
[24]Wang Y P, Zhou L, Zhang M L, et al. Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering, Appl. Phys. Lett.2004,84:1731
[25]Aurivillius B, Mixed bismuth oxides with layer lattices. Ark. Kemi 1949,1:463-471
[26]Wang J, Neaton J B, Zheng H, Nagarajna V, et al. Epitaxial BiFeO3 multiferroic thin film heterostructures, Science 2003,299:1719-1722
[27]Kanai T, Ohkoshi S, Nakajima A, et al. A ferroelectric ferromagnet composed of (PLZT)x(BiFeO3)1-x solid solution, Advanced Materials 2001,13:487-490
[28]Park S, Hur N, Guha S, et al. Percolative Conduction in the Half-Metallic-Ferromagnetic and Ferroelectric Mixture of (La, Lu, Sr)MnO3. Physical Review Letters 2004,92:167206
[29]Paik H, Kim H C, No K, et al. Structural and physical properties of room temperature stable multiferroic properties of single-phase (Bi0.9La0.1)Fe03—Pb(Fe 0.5Nb0.5)03 solid solution systems, Journal of Applied Physics 2009,105:07D919
[30]Jeong Seog Kim, Chae II Cheon, Yong Nam Choi, et al. Ferroelectric and ferromagnetic properties of BiFeO3-PrFeO3-PbTiO3 solid solutions J. Appl. Phys. 2003,93:9263
[31]Jungho Ryu., Shashank Priya., and Kenji. Uchino, Magnetoelectric Effect in composites of mangetostrictive and piezoelectric materials, J. Electro. Ceramics. 2002,8:107-119
[32]V. R. Palkar, J. John, and R. Pinto, Observation of saturated polarization and dielectric anomaly in magnetoelectric BiFeO3 thin films,Appl. Phys. Lett.2002, 80:1628-1630
[33]Su-Chul Yang, Ashok Kumar, Valeri Petkov, and Shashank Priya, Room-temperature magnetoelectric coupling in single-phase BaTiO3-BiFeO3 system, J. Appl. Phys.2013,113:144101
[34]Rontgen W C, Schneider J. Ueber die Compressibilitat des Wassers, Annalen der Physik 1888,269:644-660.
[35]Curie P, First discussion of an intrinsic correlation between magnetic and electric properties, J Physique 1894,3:393
[36]Debye P, Introduction of the term "magnetoelectric" for these correlations, Z Phys, 1926,36:300
[37]Folen V., Rado G, Stalder E. Anisotr opy of the magnetoelectric effect in Cr2O3, Physical Review Letters 1961,6:607-608
[38]Hornreich R M, Shtrikman S. Theory of gyrotropic birefringence, Physical Review, 1968,171:1065
[39]M. HornreichjThe magnetoelectric effect:some likely candidates, Solid State Commun.1969,7:1081-1088
[40]段纯刚,磁电效应研究进展,物理学进展2009,29：215-238
[41]Shin K.H., Inoue M., Arai K., Preparation and Properties of elastically coupled electromagnetic elements with a bonding structure, IEEE.Trans.Magn.1998, 34:1324
[42]Naoshi Ikeda, Hiroyuki Ohsumi, Kenji Ohwada, Kenji lshii, Toshiya Inami, et al. Ferroelectricity from iron valence ordering in the charge-frustrated system LuFe2O4, Nature Letters 2005,436:04039
[43]Nan C. W. Magnetoelectric effect in composites of piezoelectric and piezomagnetic phases. Physical Review B,1994,50:6082
[44]Huang Z., Cao Y., Sun Y., et al. Coupling between the ferroelectric and antiferromagnetic orders in YMnO3. Physical Review B 1997,56:2623
[45]Tomuta D G, Ramakrishnan S,Nieuwenhuys G J, Mydosh J A, J. Phys:Condens. Matter.2001,13:4543.
[46]Kimura T., Kawamoto S., Yamada I., et al. Magnetocapacitance effect in multiferroic BiMnO3. Physical Review B 2003,67:180401
[47]Goto T., Kimura T., Lawes G, et al. Ferroelectricity and giant magnetocapacitance in perovskite rare-earth manganites. Physical Review Letters 2004,92:257201
[48]Hur N., Park S., Sharma P. A., et al. Colossal Magnetodielectric Effects in DyMn2O5. Physical Review Letters 2004,93:107207
[49]Bibes M, Barth L MY A. Multiferroics:Towards a magnetoelectric memory. Nat Mater.2008,7:425-426
[50]Chu Y H, Martin L W, Hoicomb M B, et al. Electric-field control of local ferromagnetism using a magnetoelectric multiferroic, Nat Mater.2008,7:478-482
[51]Bibes M, Barthelemy A. Multiferroics:Towards a magnetoelectric memory, Nature materials 2008,7:425-426
[52]施展,王翠萍,刘兴军等.,基于磁电复合材料的四态存储器,科学通报2008,53：1177-1179
[53]Yang F, Zhou Y C, Tang M H, et al. Eight-logic memory cell based on multiferroic junctions, J Phys D Appl Phys 2009,42:072004
[54]Yang F, Tang M H, Ye Z, et al. Eight logic states of tunneling magnetoelectroresistance in multiferroic tunnel junctions, J Appl. Phys.2007, 102:044504.
[55]Zhang L B, Tang M H, Yang F. Sixteen resistive states of a tunnel junction with a composite barrier, Eur Phys J Appl Phys,2010,51:10604
[56]Michel C, Moreau J M, Achenbache G D, et al. The Atomic Structure of BiFeO3, Solid State Communications 1969,7:701-704
[57]Moreau J M, Michel C, Gerson R, et al. Ferroelectric BiFeO3 X-ray and Neutron Diffraction Study, Journal of Physics and Chemistry of Solids,1971,32:1315-1320
[58]Bai F. M., Wang J. L.,Wuttig M., et al. Destruction of spin cycloid in (111)c-oriented BiFeO3 thin films by epitiaxial constraint:enhanced polarization and release of latent magnetization, Appl. Phys. Lett.2005,86:032511
[59]Teague J D, Gerson R, James W J, Dielectric Hysteresis in Single Crystal BiFeO3, Solid State Communications 1970,8:1073-1074
[60]Sosnowska I, Peterlin-Neumaier T, Steichele E, Spiral Magnetic Ordering in Bismuth Ferrite, Journal of Physics C:Solid State Physics 1982,15:4835-4846
[61]Singh R S, Bhimasankaram T, Kumar G S, et al. Dielectric and magnetoelectric properties of Bi5FeTi3O15. Solid state communications 1994,91:567-569
[62]Dong X W, Wang K F, Wan J G, et al. Magnetocapacitance of polycrystalline Bi5Ti3FeO15 prepared by sol-gel method, Journal of Applied Physics 2008, 103:094101
[63]Mao XY, Wang W, Chen XB, et al. Multiferroic properties of layer-structured Bi5Fe0.5Co0.5Ti3O15 ceramics, Applied Physics Letters,2009,95:082901
[64]Wang C H, Liu Z F, Yu L, Tian Z M, Yuan S L, Structural, magnetic and dielectric properties of Bi5-xLaxTi3Co0.5Fe0.5O15 ceramics. Materials Science and Engineering B 2011,176:1243-1246
[65]Yang F J, Su P, Wei C, et al. Large magnetic response in (Bi4Nd)i3Feo.5Coo.5015 ceramic at room-temperature, Journal of Applied Physics 2011,110:126102
[66]刘顺华,刘军民,董星龙,电磁波屏蔽及吸波材料.北京：化学工业出版社,2007：58-63
[67]H. M. Musal, Jr., H. T. Hahn. Thin-layer electromagnetic absorber design, IEEE Trans. Magn.1989,25:3851-3853
[68]廖绍彬,道生戴.铁磁学(下册),北京：科学出版社,1988：87-96
[69]宛德福,马兴隆.磁性物理学,北京：电子工业出版社,1999：39-42
[70]A. Aharoni, Exchange resonance modes in a ferromagnetic sphere. J. Appl. Phys. 1991,69:7762-7764
[71]Naito Y, Suetake K. Application of ferrite to electromagnetic wave absorber and its characteristics, IEEE Trans. Microwave Theory Tech.1971,19:65-72
[72]S. A. Oliver, M. L. Chen, C. Vittoria, et.al. Properties of pulsed laser deposited scandium-doped barium hexaferrite films, J. Appl. Phys.1999,85:4630-4633
[73]Martha Pardavi-Horvath. Microwave applications of soft ferrites, J.Magn.Magn. Mater.2000,215:171-183
[74]J. L. Snoek, Dispersion and absorption in magnetic ferrites at frequencies above one Mc/s, Physica (Amsterdam) 1948,14:207-217.
[75]Shin J Y, Oh J H J. The microwave Phenomena of ferrite microwave absorbers. IEEE Trans. Magn.1993,29:3437-3439.
[76]Xiaoli Wang and Wenjuan Cao, Dielectric and ferroelectric properties of BaTiO3-(Na1/4Bi3/4)(Mg1/4Ti1/4)O3 ceramics, Appl. Phys. Lett.2007,90:042913
[77]H. C. Yu and Z. G. Ye, Dielectric properties and relaxor behavior of a new (1-x)BaTiO3-xBiAlO3 solid solution. J. Appl. Phys.2008,103:034114
[78]Toshimitsu Kanai, Shin—ichi Ohkoshi, Akira Nakajima, et al. A Ferroelectric Ferromagnet Composed of (PLZT)x(BiFeO3)1-x Solid Solution. Adv Mater 2001,13: 487-490
[79]Kumar M. M., Srinvas A., Kumar G S., et al. Investigation of the magnetoclectrie effecting BiFeO3-BaTiO3 solid solutions. Journal of Physiics Condensed Matter, 1999,11:8131-8139
[80]Chen Ang and Zhi Yu, High remnant polarization in (Sro.7Bio.2)Ti03-(Nao.5Bio.5)Ti03 solid solutions, Appl. Phys. Lett.2009,95:232908
[81]Dorcet V, Marchet P, OPena, et al. Properties of the solid solution(1-x)Nao.5Bio.5Ti03-xBiFe03, J Magn Magn Mater.2009,321:1762-1766
[82]Ma Yan and Chen XiangMing, Enhanced multiferroic characteristics in NaNbO3-modified BiFeO3 ceramics, J Appl. Phys.2009,105:054107
[83]Mehrotra Vivek, Russell Michael W, Giannelis Emmanuel P, et al, Magnetic and optical properties of y-Fe2O3 nanocrystals, J Appl Phys 1993,73:5109
[84]Tae-Jin Park, Sharadha Sambasivan, Daniel A Fischer, et al. Electronic Structure and Chemistry of Iron-Based Metal Oxide Nanostructured Materials:A NEXAFS Investigation of BiFeO3, Bi2Fe4O9, α-FeO3,γ-FesCb, and Fe/Fe3O4, J Phys Chem C 2008,112:10359-10369
[85]Hu W M, Su L W, Ye Z G, et al. Enhanced Magnetization and Polarization in Chemically Modified Multiferroic (1-x)BiFe03-xDyFe03 Solid Solution, Applied Physics Letters 2009,94:142908
[86]Cheon C L, Kim J S, Jang P W, Ferroelectric and Magnetic Properties of PrFeO3-PbTiO3 and PrFeO3-BiFeO3-PbTiO3 Thin Films, Japanese Journal of Applied Physics 2002,41:6777-6780
[87]P. A. Joy, S. K. Date, Comparison of the zero-field-cooled magnetization behavior of some ferromagnetic and ferrimagnetic systems. J. Magn. Magn. Mater.2000, 218:229
[88]S. P. McAlister, J. K. Furdyna,W. Giriat. Magnetic susceptibility and spin-glass transition in Zn1-xMnxFe. Phys. Rev. B 1984,29:1310
[89]Sosnowska I, Neumaier T P, Steichele E. Spiral magnetic ordering in bismuth ferrite, Journal of Physics C:Solid State Physics 1982,15:4835
[90]Venkata Ramana E, Suryanarayana S V, Bhima Sankaram T. Synthesis and magnetoelectric studies on Na0.5Bi0.5Ti03-BiFe03 solid solution ceramics, Solid State Sciences 2010,12:956-962
[91]Dorcet V, Marchet P, Pena O, et al. Properties of the solid solution (1-x)Na0.5Bi0.5Ti03-xBiFe03, J. Magn. Magn. Mater.2009,321:1762-1766
[92]Singh, K., et al. Dielectric and magnetic properties of (BiFeO3)1-x(PbTiO3)x ferromagnetoelectric system. Solid State Communications 2008,148:18-21
[93]Wang T H, Ding Y, Tu C S, et al. Structure, magnetic, and dielectric properties of (1-x)BiFeO3-xBaTiO3 ceramics, Journal of Applied Physics 2011,109:07D907
[94]I. H. Ismailzade, et al. Magnetoelectric Investigation of the System BiFeO3-Pb(Fe0.5Nb0.5)03, Phys. Status Solidi A 1980,57:99-103
[95]Wang D H, Goh W C, Ning M, et al. Effect of Ba doping on magnetic, ferroelectric, and magnetoelectric properties in mutiferroic BiFeO3 at room temperature, Applied physics letters 2006,88:212907
[96]B. Bhushan, A. Basumallick, et al. Sr induced modification of structural, optical and magnetic properties in Bi1-xSrxFeO3 (x=0,0.01,0.03,0.05 and 0.07) multiferroic nanoparticles, Solid State Sciences 2010,12:1063-1069
[97]Jia-Huan Xu, Hua Ke, et al. Microwave-dielectric and magnetic properties of Ta-doped BiFeO3 nanopowders, Philosophical Magazine. Letters 2009,89:701-710
[98]FushengWen, Nan Wang, Fang Zhang, Enhanced microwave absorption properties in BiFeO3 ceramics prepared by high-pressure synthesis, Solid State Communications 2010,150:188-1891
[99]赵新闻,韩建华,周克省,秦宪明,邓联文,陈颖,夏辉。Bi1-xLaxFeO3多铁体系的微波吸收性能,中南大学学报(自然科学版),2011,42：3315-3319
[100]H. Singh, A. Kumar, K. L. Yadav, Structural, dielectric, magnetic, magnetodielectric and impedance spectroscopic studies of multiferroic BiFeO3-BaTiO3 ceramics, Mater. Sci. Eng. B 2011,176:540-547
[101]Dorcet V, Trolliard G, Boullay P, The structural origin of the antiferroelectric properties and relaxor behavior of Na0.5Bi0.5TiO3, J. Magn. Magn. Mater.2009, 321:1758-1761
[102]Wen Z, You L, Shen X, et al. Multiferroic properties of(Bi1-xPrx)(Fe0.95Mn0.05) O3 thin films, Mater. Sci. Eng. B 2011,176:990-995
[103]S X Zhang, W J Luo, L. Wang, Y W Ma; Simultaneously improved magnetization and polarization in BiFeO3 based multiferroic composites, J. Appl. Phys.2010, 107:054110
[104]Yuan G L, Or S W, Enhanced piezoelectric and pyroelectric effects in single-phase multiferroic Bi1-xNdxFeO3 (x=0-0.15) ceramics, Appl. Phys. Lett.2006,88:062905
[105]Fischer P, Polomska M, Sosnowska I, et al. Temperature dependence of the crystal and magnetic structures of BiFeO3, J. Phys. C:Solid State Phys.1980, 13:1931-1940
[106]C. Ederer, N. A. Spaldin, Influence of strain and oxygen vacancies on the magnetoelectric properties of multiferroic bismuth ferrite, Phys. Rev. B 2005, 71:224103
[107]T. Kanai, S.I. Ohkoshi, A. Nakajima, et al. A ferroelectric ferromagnet composed of (PLZT)(x)(BiFeO3)(1-x) solid solution, Adv. Mater.2001,13:487-490
[108]Ueda K, Tabata H, Kawai T. Coexistence of ferroelectricity and ferromagnetism in BiFeO3-BaTiO3 thin films at room temperature, Appl. Phys. Lett.1999,75:555-557
[109]Kanai T, Ohkoshi S, Hashimoto K. Magnetic, electric, and optical functionalities of (PLZT)x(BiFeO3)1-x ferroelectric-ferromagnetic thin films, J. Phys. Chem. Solids 2003,64:391-397.
[110]Geck J, Buchner B, Hiicker M, et al. Evidence for canted antiferromagnetism in lightly doped La1-xSrxMnO3, Phys. Rev. B 2001,64:144430
[111]Kumar M M, Palkar V R, Srinivas K, et al. Ferroelectricity in a pureBiFeO3 ceramic, Appl. Phys. Lett.2000,76:2764-2766.
[112]Jun Y K, Moon W T, Chang C M, et al. Effects of Nb-doping on electric and magnetic properties in multi-ferroic BiFeO3 ceramics, Solid State Commun.2005, 135:133-137
[113]Ruette B, Zvyagin S, Pyatakov A P, et al. Magnetic-field-induced phase transition in BiFeO3 observed by high-field electron spin resonance:Cycloidal to homogeneous spin order, Phys. Rev. B 2004,69:064114
[114]Wongdamnern N, Triamnak N, Unruan M, et al. Sub-coercive field dynamic hysteresis in morphotropic phase boundary composition of Pb(Zr1/2Ti1/2)O3-Pb(Zn1/3Nb2/3)O3 ceramic and its scaling behavior, Phys. Lett. A 2010,374:391-395.
[115]Wongdamnern N, Triamnak N, Ngamjarurojana A, et al. Stress-dependent scaling behavior of sub-coercive field dynamic hysteresis in Pb(Zr1/2Ti1/2)O3-Pb(Zn1/3Nb2/3)O3 ceramic systems, Ferroelectrics 2009,384:1-9.
[116]Mishra R K, Pradhan D K, Choudhary R N P, et al. Dipolar and magnetic ordering in Nd-modified BiFeO3 nanoceramics, J. Magn. Magn. Mater.2008, 320:2602-2607.
[117]Kumar M, Yadav K L, Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization, Appl. Phys. Lett.2007,91:242901
[118]M. Kumar, K. L. Yadav, Study of room temperature magnetoelectric coupling in Ti substituted bismuth ferrite system, J. Appl. Phys.2006,100:074111
[119]Shao T, Scholl A, Zavaliche F, et al. Electrical control of antiferromagnetic domain in multiferroic BiFeO3 film at room temperature, Nat. Mater.2006,5:823-829
[120]R. Mazumder, P.S. Devi, D. Bhattacharya, et al. Ferromagnetism in nanoscale BiFeO3, Appl. Phys. Lett.2007,91:062510
[121]Wang N, Cheng J, Pyatakov A, et al. Multiferroic properties of modified BiFeO3-PbTiO3-based ceramics:Random-field induced release of latent magnetization and polarization, Physical Review B,2005,72:104434
[122]Srinivas A, Kim D W, Hong K S, et al. Study of magnetic and magnetoelectric measurements in bismuth iron titanate ceramic—Bi8Fe4Ti3O24, Mater. Res. Bull. 2004,39:55-61
[123]Srinivas A, Suryanarayana S V, Kumar G S, et al. Magnetoelectric measurements on and, J. Phys.:Condens. Matter 1999,11:3335
[124]B. Aurivillius, Ark. Kemi, Mixed oxides with layer lattices. Ⅲ. Structure of BaBi4Ti4O15,1950:519
[125]Snedden A, Hervoches C H, Lightfoot P. Ferroelectric phase transitions in SrBi2Nb2O9 and Bi5Ti3FeO15：A powder neutron diffraction study, Phys. Rev. B 2003,67:092102
[126]Singh R S, Bhimasankaram T, Kumar G S, et al. Dielectric and magnetoelectric properties of Bi5FeTi3O15, Solid State Commun.1994,91:567-569
[127]Suryanarayana S V, et al. Magnetoelectric coupling in Bi5Ti3FeO15 ceramics, Journal of Physics:Condensed Matter,1999,15:627-631
[128]A.R. James, G.S. Kumar, et al. The dielectric and electrical properties of four layered LaBi4FeTi4O15, Ferroelectrics 1998,216:11-26
[129]Mao X, Wang W, Chen X, et al. Multiferroic properties of layer-structured Bi5Fe0.5Co0.5Ti3O15 ceramics, Appl. Phys. Lett.2009,95:082901
[130]Dong X W, Wang K F, Wan J G, et al. Magnetocapacitance of polycrystalline Bi5Ti3FeO15 prepared by sol-gel method, J. Appl. Phys.2008,103:094101.
[131]Li J B, Huang Y P, Rao G H, et al. Ferroelectric transition of Aurivillius compounds Bi5Ti3FeO15 and Bi6Ti3Fe2O18, Appl. Phys. Lett.2010,96:222903
[132]Mao X Y, Wang W, Chen X B. Electrical and magnetic properties of Bi5FeTi3O15 compound prepared by inserting BiFeO3 into Bi4Ti3O12, Solid State Commun.2008, 147:186-189
[133]Horn J A, Zhang S C, Selvaraj U, et al. Templated grain growth of textured bismuth titanate, J. Am. Ceram.Soc.1999,82:921-926
[134]Zhang H, Kajiyoshi K. Hydrothermal Synthesis and Size Dependent Properties of Multiferroic Bismuth Ferrite Crystallites, J. Am. Ceram. Soc.2010,93:3842-3849
[135]Li J B, Huang Y P, Rao G H, et al. Ferroelectric transition of Aurivillius compounds< of Aurivillius compounds Bi5Ti3FeO15 and Bi6Ti3Fe2O18. Appl. Phys. Lett.2010,96:222903
[136]Suarez D Y, Reaney I M, Lee W E. Relation between tolerance factor and Tc in Aurivillius compounds, J. Mater. Res.2001,16:3139-3149
[137]Ferrarelli M C, Tan C C, Sinclair D C. Ferroelectric, electrical, and structural properties of Dy and Sc co-doped BaTiO3, J. Mater. Chem.2011,21:6292-6299
[138]Wu Y J, Gao Y, Chen X M, et al. Dielectric relaxations in Tb0.91Yb1.38Bi1.71Fe5O12 ceramics, Phys. Lett. A 2009,373:1089-1092
[139]Srinivas A, Kim D W, Hong K S, et al. Observation of ferroelectromagnetic nature in rare-earth-substituted bismuth iron titanate, Appl. Phys. Lett.2003,83:2217-2219
[140]Rout S K, Sinha E, Hussian A, et al. Phase transition in ABi3Ti3O12 (A= Ca, Sr, Ba) Aurivillius oxides prepared through a soft chemical route, J. Appl.Phys.2009, 105:024105
[141]Scott J F, Araujo C A, Melnick B M, et al. Quantitative measurement of space-charge effects in lead zirconate-titanate memories, J. Appl. Phys.1991, 70:382-388
[142]Ang C, Yu Z, Cross L E. Oxygen-vacancy-related low-frequency dielectric relaxation and electrical conduction in Bi:SrTiO3, Phys. Rev. B 2000,62:228
[143]Zhong Z, Ishiwara H. Variation of leakage current mechanisms by ion substitution in BiFeO3 thin films, Appl. Phys. Lett.2009,95:112902
[144]Naganuma H, Miura J, Okamura S. Annealing temperature effect on ferroelectric and magnetic properties in Mn-added polycrystalline BiFeO3 films, J. Electroceram. 2009,22:203-208
[145]Ma Y, Chen X M. Enhanced multiferroic characteristics inNaNbO3-modified BiFeO3 ceramics, J. Appl. Phys.2009,105:054107
[146]Wang D H, Goh W C, Ning M, et al. Effect of Ba doping on magnetic, ferroelectric, and magnetoelectric properties in mutiferroic BiFeO3 at room temperature, Appl. Phys. Lett.2006,88:212907
[147]Bai W, Gao Y Q, Zhu J Y, et al. Electrical, magnetic, and optical properties in multiferroic Bi5Ti3Fe015 thin films prepared by a chemical solution deposition route, J Appl Phys 2011,109:064901
[148]Jang J S, Yoon S S, Borse P H, Lim K T, Hong T E, Jeong E D, et al. Synthesis and characterization of aurivillius phase Bi5Ti3FeO15 layered perovskite for visible light photocatalysis, J Ceram Soc Jpn 2009,117:1268-1272
[149]Bi H, Li SD, Zhang YC, Du YW, Ferromagnetic-like behavior induced by lattice distortion of ultrafine NiO nanocrystallites. J Magn Magn Mater 2004,277:363-367
[150]Berkowitz AE, Lahut JA, Jacobs IS, Levinson LM, Forester DW, Spin pinning at ferrite-organic interfaces, Phys Rev Lett 1975,34:594
[151]Nogues J, Sort J, Langlais V, et al. Exchange bias in nanostructures, Phys Rep 2005, 422(3):65-117
[152]Geshev J. J., Comment on "Exchange bias in the layered cobaltite Sr1.5Pr0.5CoO4, J Appl Phys 2009,105:066108
[153]Sun SM, Wang WZ, Xu HL, Zhou L, et al. Bi5FeTi30i5 Hierarchical Microflowers: Hydrothermal Synthesis, Growth Mechanism, and Associated Visible-Light-Driven Photocatalysis, J Phys. Chem. C 2008,112:17835-17843
[154]Preethi Meher K R S, Varma K B R. Bi4Ti3O12-5BiFeO3 Aurivillius intergrowth: Structural and ferroelectric properties, J. Appl. Phys.2009,106:124103
[155]S. A. Kizhaev, G. D. Sultanov and F. A. Mirishli, James A R, Bhimasankaram T. Electrical and Magnetic Studies on SrBi5FeTi4O18, Sov. Phys. Solid State,1973,15, 214-218
[156]Jartych E, Mazurek M, Lisinska-Czekaj A, et al. Hyperfine interactions in some Aurivillius Bim+1Ti3Fem-3O3m+3 compounds, J. Magn. Magn. Mater.2010, 322:51-55.
[157]Patri S K, Choudhary R N P, Samantaray B K. Studies of structural, dielectric and impedance properties of Bi9Fe5Ti3O27 ceramics, J. Electroceram 2008,20:119-126
[158]Kojima T, Watanabe T, Funakubo H, et al. Ferroelectric properties of lanthanide-substituted Bi4Ti3O12 epitaxial thin films grown by metalorganic chemical vapor deposition, J. Appl. Phys.2003,93:1707
[159]Z. V. Gabbasova, M. D. Kuz'min, A. K. Zvzdin, I. S. Dubenko, V. A. Murashov, D. N. Rakov and I. B. Krynetsky, Bi1-xRxFeO3 (R=rare earth):a family of novel magnetoelectrics Phys. Lett. A,1991,158,491-498
[160]Ramana E V, Suryanarayana S V, Sankaram T B. ac impedance studies on ferroelectromagnetic SrBi5-xLaxTL4FeO18 ceramics, Mater. Res. Bull.2006, 41:1077-1088.
[161]Singh R S, Bhimasankaram T, Kumar G S, et al. Dielectric and magnetoelectric properties of Bi5FeTi3O15, Solid state communications,1994,91:567-569
[162]Kumar S, Varma K B R. Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics, J Phys D: Appl Phys 2009,42:075405.
[163]Noguchi Y, Miyayama M. Large remanent polarization of vanadium-doped Bi4Ti3O12, Appl. Phys. Lett.2001,78:1903-1905
[164]Chen X B, Hui R, Zhu J, et al. Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics, J Appl. Phys.2004,96:5697-5700
[165]Yuan G L, Or S W, Liu J M, et al. Structural transformation and ferroelectromagnetic behavior in single-phase BiNdFeO multiferroic ceramics, Appl. Phys. Lett.2006,89:052905
[166]Wang D H, Goh W C, Ning M, et al. Effect of Ba doping on magnetic, ferroelectric, and magnetoelectric properties in mutiferroic BiFeO3 at room temperature, Appl. Phys. Lett.2006,88:212907
[167]Alvarez-Fregoso O. Structural and dielectric characterization of SmBiTiO ferroelectric ceramics, J. Appl. Phys.1997,81:1387
[168]Horn J A, Zhang S C, Selvaraj U, et al. Templated grain growth of textured bismuth titanate, J. Am. Ceram. Soc.1999,82:921-926
[169]E. V. Ramana and T. B. Sankaram, Magnetoelectric investigations in La-modified bismuth layered ferroelectromagnetics, Mater. Chem. Phys.2010,120,231-235
[170]Uniyal P, Yadav K L. Pr doped bismuth ferrite ceramics with enhanced multiferroic properties, J. Phys.:Condens. Matter 2009,21:405901
[171]Phuoc N N, Phu Thuy N, Anh Tuan N, et al. Coexistence of positive and negative exchange bias in CrMn/Co bilayers, J. Magn. Magn. Mater.2006,298:43-47
[172]Punnoose A, Morales E H, Wang Y, et al. Hysteretic ferromagnetic resonance as a probe for coercivity, exchange bias, and loop asymmetry, J. Appl. Phys.2003, 93:771-773
[173]Kanai T, Ohkoshi S, Nakajima A, et al. A ferroelectric ferromagnet composed of (PLZT)x(BiFeO3)1-x solid solution, Adv. Mater.2001,13:487-490
[174]Cross L E. Relaxorferroelectrics:An overview, Ferroelectrics,1994,151:305-320
[175]Withers R L, Thompson J G, Rae A D. The crystal chemistry underlying ferroelectricity in Bi4Ti3O12, Bi3TiNb09, and Bi2WO6, J. Solid State Chem.1991, 94:404-417
[176]Chen X B, Hui R, Zhu J, et al. Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics, J. Appl. Phys.2004,96:5697-5700
[177]Huang S, Sun L, Feng C, et al. Relaxor behavior of layer structured SrBi1.65La0.35Nb209, J. Appl. Phys.2006,99:076104
[178]Kholkin A L, Avdeev M, Costa M E V, et al. Dielectric relaxation in Ba-based layered perovskites, Appl. Phys. Lett.2001,79:662-664
[179]Shvartsman V V, Costa M E V, Avdeev M, et al. Relaxor Behavior of BaBi2Ta2O9 and BaBi2Nb2O9 Ceramics, Ferroelectrics 2003,296:187-197
[180]Freitas R S, Mitchell J F, Schiffer P. Magnetodielectric consequences of phase separation in the colossal magnetoresistance manganite Pr0.7Ca0.3MnO3, Phys. Rev. B 2005,72:144429
[181]Shireen A, Saha R, Mandal P, et al. Multiferroic and magnetodielectric properties of the Al1-xGaxFeO3 family of oxides, J. Mater. Chem.2011,21:57-59
[182]Catalan G, Magnetocapacitance without magnetoelectric coupling, Appl. Phys. Lett. 2006,88:102902
[183]Catalan G, Scott J F. Magnetoelectrics:Is CdCr2S4 a multiferroic relaxor?, Nature 2007,448:E4-E5
[184]Zhang X, Sui Y, Wang X, et al. Influence of diamagnetic Pb doping on the crystal structure and multiferroic properties of the BiFeO3 perovskite, J. Appl. Phys.2009, 105:07D918
[185]T. Katsufuji and H. Takagi, Magnetocapacitance and spin fluctuations in the geometrically frustrated magnets R2Ti2O7 (R=rare earth), Phys. Rev. B 2004, 69:064422