钙钛矿锰氧化物La_(0.8-x)Eu_xSr_(0.2)MnO_3(x=0,0.05)的磁性和磁熵变研究
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摘要
本篇文章主要研究钙钛矿氧化物La_(0.8-x)Eu_xSr_(0.2)MnO_3(x=0,0.05)中A位掺杂铕(Eu)后对样品的磁性和磁熵变的影响.采用传统的固相反应法制备多晶样品,根据数据拟合得到XRD图像和晶格参数,通过对两样品的M-T曲线和M-H曲线研究发现:x=0和x=0.05两样品在高温区均表现出顺磁性,居里温度T_c分别为283 K(x=0)和284 K(x=0.05),且在居里温度附近表现出铁磁性.随着掺杂量增加,样品的居里外斯温度降低(θ_(x=0)=322 K、θ_(x=0.05)=304 K),表明Eu~(3+)掺杂改变了系统内的铁磁耦合.在7 T磁场下磁熵变的最大值分别为2.73 J/kg·K和4.19 J/kg·K,表明Eu~(3+)掺杂使得最大磁熵变值增大.对比制冷效率,发现该系列样品具有作为磁制冷材料的潜质.
In this thesis, we mainly study the effect of A site doping Eu on the magnetic and magnetic entropy change of La_(0.8-x)Eu_xSr_(0.2)MnO_3(x=0,0.05). The polycrystalline samples were prepared by the traditional solid-state reaction method. According to the analysis of XRD data, there was no obvious impurity peak after the Eu incorporation, and the imaging was good. The results of M-T and M-H curves of two samples show that the two samples show paramagnetism above 374 K, the Curie temperature T_c is 283 K(x =0) and 284 K(x=0.05), and shows ferromagnetism near the Curie temperature and weak antiferromagnetism at the low temperature. As the doping amount increases, the Curie temperature decreases(θ_(x=0)=322 K, θ_(x=0.05)=304 K), indicating that the doping of Eu~(3+) Ferromagnetic coupling. The maximum values of magnetic entropy change at 7 T magnetic field are 2.73 J/kg · K and 4.19 J/kg · K, respectively, indicating that the maximum magnetic entropy change increases with the doping of Eu~(3+). Comparing the refrigeration efficiency, we found that this series of samples has potential as a magnetic refrigeration material.
In this thesis, we mainly study the effect of A site doping Eu on the magnetic and magnetic entropy change of La_(0.8-x)Eu_xSr_(0.2)MnO_3(x=0,0.05). The polycrystalline samples were prepared by the traditional solid-state reaction method. According to the analysis of XRD data, there was no obvious impurity peak after the Eu incorporation, and the imaging was good. The results of M-T and M-H curves of two samples show that the two samples show paramagnetism above 374 K, the Curie temperature T_c is 283 K(x =0) and 284 K(x=0.05), and shows ferromagnetism near the Curie temperature and weak antiferromagnetism at the low temperature. As the doping amount increases, the Curie temperature decreases(θ_(x=0)=322 K, θ_(x=0.05)=304 K), indicating that the doping of Eu~(3+) Ferromagnetic coupling. The maximum values of magnetic entropy change at 7 T magnetic field are 2.73 J/kg · K and 4.19 J/kg · K, respectively, indicating that the maximum magnetic entropy change increases with the doping of Eu~(3+). Comparing the refrigeration efficiency, we found that this series of samples has potential as a magnetic refrigeration material.
引文
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[3] KameliP,Salamati H,Hakimi M,Journal of Alloys and Compounds,463(2008),18.
[4] 唐贵德,刘兴民,刘力虎,功能材料,35(2004),434.
[5] Chen P,Du Y W,Chinese Journal of Physics,39(2001),357.
[6] Nam D N H,Jonason K,Nordblad P,Physical Review B,59(1999),4189.
[7] Mukherjee S,Ranganathan R,Anikumar P S,Phys.Rev B,54(1996),9267.
[8] 刘宁,严国清,毛强,等,物理学报,59(2010),5759.
[9] Wang G Y,Liu P,Li L,Ye W M,Liu N,Peng Z S,Chinese Journal of Rare Metals,39(2015),421.
[10] Wang Z M,Xu Q Y,Ni G,Zhang H,Phys B Condensed Matter,406(2011),4333.
[11] 孙晓东,徐宝,吴鸿业,物理学报,15(2017),1000.
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[20] Mira J,Rivas J,Mod Phys Lett B,18(2004),725.