化合物DyMn_6Sn_6的磁晶各向异性及自旋重取向相变研究

Magnetocrystalline anisotropy and spin-reorientation transition of compound DyMn_6Sn_6

采用交换相互作用的分子场理论模型对金属间化合物DyMn6Sn6的自旋重取向相变进行了研究。从理论上计算了DyMn6Sn6的易磁化方向以及Dy和Mn离子磁矩与c轴夹角随温度的变化。基于单离子模型计算了Dy离子的一阶和二阶磁晶各向异性常数K1R和K2R随温度的变化。研究表明,为了很好的描述该化合物的自旋重取向相变,必须考虑Dy离子的四阶晶场项及相应的二阶磁晶各向异性常数K2R、K2R与K1R和Mn离子磁各向异性常数K1t之间的相互竞争是导致DyMn6Sn6自旋重取向相变的重要因素。

The molecular field theory of exchange interaction has been applied to investigate the spin-reorientation transition in intermetallic compound DyMn6Sr6. The theoretically calculated temperature dependence of easy magnetization direction has a very good agreement with the experimental data. The temperature dependence of magnetocrystalline anistropic constants of Dy ion K1R and K2R have been calculated in the framework of single ion model. Our studies show that the fourth-order crystal field parameter B4^0 and the corresponding second-order magnetocrystalline anistropic constant K2R of Dy ion have to be taken into account in order to explain the spinreorientation transition. The competition between K2R and K1R plays an important role in the spin-reorientation transition in DyMn6Sn6.