金属间化合物RMn_2Ge_2(R=La,Pr,Nd,Sm,Gd,Tb和Y)中的自发磁相变及相变时的磁弹性异常

SPONTANEOUS MAGNETIC PHASE TRANSITION AND MAGNETOELASTIC ANOMALIES AT TRANSITIONS IN INTERMETALLIC COMPOUNDS RMn_2Ge_2 (R=La,Pr,Nd,Sm,Gd,Tb,Y)

在 10— 80 0K的温度范围内用X射线衍射方法测量了RMn2 Ge2 (R =La ,Pr,Nd ,Sm ,Gd ,Tb和Y)的晶格常数与温度的变化关系 .在各种类型的自发磁相变观察到晶格常数的磁弹性异常现象 .实验得出 ,自发磁相变时的磁弹性异常主要由Mn次晶格引起 ,并且Mn Mn交换相互作用能不仅与晶格常数a有关 ,而且与晶格常数c有关 .用Kittle的交换反转模型讨论了低温时的铁磁—反铁磁一阶相变 .

The temperature dependence of lattice constants a and c of intermetallic compounds RMn\-2Ge\-2 (\%R\%=La,Pr,Nd,Sm,Gd,Tb and Y)is measured in the temperature range 10—800?K using the X\|ray method. The magnetoelastic anomalies of a(T) and c(T) are found at different spontaneous magnetic phase transitions. It is shown that the magnetoelastic anomalies are mainly determined by the Mn\|subsystem. Mn\|Mn exchange interactions depend not only on the lattice constant a but also on constant c. Low\|temperature ferromagnetic\|antiferromagnetic transitions are discussed in the framework of Kittle's exchange inversion model.