磁电耦合对于多铁性材料CdCr2S4介电性质的影响

多铁性材料CdCr2S4在实验中被观测到的磁相变温度附近的介电异常现象，为一定温度区间内共存的弛豫铁电性和铁磁性提供了磁电耦合的依据。基于SRBRF模型和Heisenberg模型，我们提出形如 的磁电耦合形式，并计算出了最近邻磁自旋对关联 。最近邻自旋对关联 通过磁电耦合修正阻碍极化翻转的激活能的大小，使得被冻结在某一特定方向上的极化又能够在其它的可能取向上进行热翻转，改变了极化弛豫时间的分布，从而导致了介电性质在磁相变温度附近发生介电异常。同时，考虑磁场对介电性质的影响，得出的磁电容效应和实验数据很好吻合进一步证实了我们想法的正确性。

Magnetoelectric Coupling Dependent Dielectric Properties in Multiferroics CdCr2S4

In multiferroics CdCr2S4, the dielectric constant exhibits a sharp increase around the magnetic-phase-transition temperature, which offers a symbol for the magnetoelectric coupling interaction between the relaxor ferroelectricity and magnetic order. Based on SRBRF model and Heisenberg model, we propose an advisable magnetoelectric coupling term of , and give the value of spin-pair-correlation. It is indicated that the dielectric anomaly below magnetic-phase-transition temperature is attributed to the reason that the activation energy against polar clusters reorientation and relaxation time are amended by the spin-pair-correlation via the magnetoelectric coupling. Moreover, we consider the influence of the external magnetic field in dielectric constant. The obtained real part of dielectric constants and the magnetocapacitance are in good agreement with the experimental results which confirm the correctness of our idea.