The temperature- and field-induced magnetic phase transitions in pseudoternary systems Tb1−xYxMn2Ge2 and Tb1−xYxMn2Si2, which are characterized by a separate magnetic ordering of the Mn and Tb subsystems, have been studied on strongly textured samples by magnetization and thermal expansion measurements. In the concentration region 0.4≤ x≤ 1.0, where the Mn moments are ordered only, the magnetic structure is antiferromagnetic. The magnetic ordering in the Tb subsystem is accompanied by a transformation of the Mn magnetic structure. As a result, the compounds show a spontaneous magnetization. This transition is of a first-order type. In both systems the transition temperature for the Tb subsystem TC(Tb) decreases linearly with increasing Y concentration and goes to zero at about x=0.40. Canted phases and field-induced first-order transitions into the collinear phase have been observed in both systems below this temperature. It is concluded that the f–d exchange interaction is the primary factor governing the value of TC(Tb).
Dubenko, I. S., Gaidukova, I. Y., Granovsky, S. A., Inoue, K., Markosyan, A. S., Roy, S. and Ali, N.. "Magnetic Phase Transitions in (Tb,Y)Mn2M2 (M=Ge and Si) Systems." (May 2003).