基于Landau二级相变理论的磁热效应分析  

Analysison field dependence of magnetocaloric effect bythe Landau theory of second-order phase transitions

作　　者：车正哲 李英楠 李凤华 金正铁 CHE Zhengzhe;LI Yingnan;LI Fenghua;Jin Zhengtie(School of Metallurgy, Northeastern University, Shenyang 110819, China;Institute of Natural Sciences, Kim Hyong Jik Normal University, Pyongyang, Korea;Institute of Silicic Acid, National Academy of Sciences, Pyongyang, Korea)

机构地区：[1]东北大学冶金学院,沈阳110819 [2]金亨稷师范大学自然科学研究所,朝鲜平壤 [3]国家科学院硅酸研究所,朝鲜平壤

出　　处：《功能材料》2020年第4期4132-4135,共4页Journal of Functional Materials

基　　金：国家自然科学基金资助项目(U1261120)。

摘　　要：将Landau二级相变理论应用于二级磁相变材料的磁热效应,建立了磁熵变与磁场的直接关系表达的理论模型。以La0.7Sr0.3MnO3为例,在居里温度附近利用该理论模型和麦克斯韦关系式计算了磁熵变ΔSM,并进行了对比。结果表明基于Landau理论的计算结果与利用传统方法的计算结果相符合。而根据Landau平均场理论,二级磁相变材料中居里温度TC和磁熵变ΔSM最大的温度Tpeak不一致,但在居里温度附近ΔSM与磁场的相关性ΔSM=kH^n表达的指数为n=2/3。A theoretical model that shows the direct correlation of magnetic entropy change and magnetic field was established by using the Landau theory of second-order phase transitions.The magnetic entropy change values estimated near the Curie temperature TC using this model were then compared with those obtained using the classical Maxwell relation.The results showed an excellent concordance between theΔSM values estimated by Landau theory and those obtained using the classical Maxwell relation.And it was shown that the Curie point TC did not coincide with the temperature Tpeak where the magnetic entropy change was maximum,but clearly demonstrated that the relationshipΔSM=kH^n with n=2/3 is valid in the temperature region near TC in the Landau mean field theory.

关 键 词：磁热效应 磁熵变 磁制冷 Landau理论 二级相变 

分 类 号：TM27[一般工业技术—材料科学与工程] TG146.1[电气工程—电工理论与新技术]