Magnetic phase diagram of the intermetallic compounds Gd_1−x La_xMn₂Ge₂ and the effect of a field on transitions of the Mn subsystem from the antiferromagnetic into the ferromagnetic state

Abstract

The magnetic properties of the intermetallic compounds Gd_1−x La_xMn₂Ge₂ (layered tetragonal crystal structure of the type ThCr₂Si₂), investigated in the present work and in [1] A. Sokolov, et al., Sol. State Commun. 105, 289 (1998), are discussed. It is shown that the basic characteristics of the magnetic ordering of these compounds—magnetic phase transitions from the ferrimagnetic into the antiferromagnetic state and vice versa—observed with increasing temperature in compositions with x < 0.1, the effect of a magnetic field on these transitions, the temperature dependences of the magnetization of these intermetallic compounds, as well as their magnetic T-x diagram can be described quantitatively in the Yafet-Kittel model for ferrimagnets with a negative exchange interaction in one of the sublattices using parameters determined in [2] A. Yu. Sokolov et al., JETP 89, 723 (1999) from investigations of the system Gd_1−x Y_xMn₂Ge₂, taking into account the dependence of the interplanar exchange interaction Mn-Mn on the crystal lattice parameter a.