金属间化合物DyMn_2Ge_2的自发磁相变和场诱导的磁相变

在 10— 80 0K的温度范围内用X射线衍射方法测量了DyMn2 Ge2 化合物的晶格常数与温度的变化关系 ,观察到高温时DyMn2 Ge2 由顺磁状态到反铁磁状态的自发磁相变伴随着晶格常数a的负的磁弹性异常现象 .在4 2K— 2 0 0K的温度范围内测量了DyMn2 Ge2 的交流磁化率 .在交换相互作用的分子场模型近似下 ,从理论上分析讨论了DyMn2 Ge2 的低温自发磁相变和场诱导的磁相变 .计算了DyMn2 Ge2 单晶的磁化强度与温度的变化关系以及不同温度下外磁场沿晶轴c方向时的磁化曲线 .理论分析和计算结果表明 ,温度低于 33K时在DyMn2 Ge2 中观察到的场诱导的一级磁相变为由亚铁磁状态 (Fi)到中间态 (IS)相变 .

SPONTANEOUS AND FIELD-INDUCED MAGNETIC PHASE TRANSITIONS IN THE INTERMETALLIC COMPOUND DyMn_2Ge_2

The temperature dependence of lattice constants a and c of intermetallic compund DyMn 2Ge 2 is measured in the temperature range 10-800K by using the X\|ray method. The magnetoelastic anomaly of lattice constants a is observed at spontaneous magnetic phase transition from paramagnetic state to antiferromagnetic state. The ac magnetic susceptibility of DyMn 2Ge 2 is measured in the temperature range 4.2-200K. Low temperature magnetic phase transitions in DyMn 2Ge 2 are discussed in the molecular field approximation by taking into account of next nearest Mn\|Mn interlayer exchange interaction. The temperature dependence of magnetization and magnetic curves at different temperatures of DyMn 2Ge 2 single crystal are calculated. Theoretical calculation shows that the observed field\|induced magnetic phase transition in DyMn 2Ge 2 single crystal at temperature lower than 33K is the transition from ferrimagnetic state into intermediate state.