磁场对多铁性材料CdCr_2S_4介电性质的影响

Effects of Magnetic Field on Dielectric Properties in Multiferroics CdCr_2S_4

多铁性材料在磁相变温度附近的介电异常归因于系统中铁磁有序和弛豫铁电性的共存。本文基于Heisenberg模型对铁磁子系统进行分析,使用最近邻自旋对关联表征磁子系统的磁有序程度。磁性质通过磁电耦合效应修正磁性离子因非中心位移而形成的极化簇的取向激活能,实现对介电性质的影响。外加磁场通过提高系统的磁有序程度而使得介电异常更为显著,磁相变温度附近的磁电容效应是磁场对介电性质影响的最好检验。

In multiferroics CdCr2 S4 , the coexistence of ferromagnetic order and relaxor ferroelectricity of system leads to the dielectric anomaly around the magnetic phase transition temperature .Based on Heisenberg model, we analyze the ferromagnetic sub-system and give the nearest neighbour spin-pair correlation showing the degree of magnetic order .Through the magnetoelectric coupling, magnetic properties amend the activation energy of polar clusters orientation which comes from the off-center displace-ment of magnetic ions, the dielectric anomaly ensues.The external magnetic field makes the dielectric anomaly more obvious via the increasing degree of magnetic order.The magnetocapacitance effect around the magnetic phase transition temperature demon-strates the relation between magnetic field and dielectric poeperties .