The magnetic properties of the intermetallic compounds Gd1-xYxMn2Ge2 (0≤x≤0.5) (tetragonal crystal structure of the type ThCr2Ge2) have been measured in fields up to 40 T in the temperature range 4.2-120 K on free powders (whose particles are free to rotate in a magnetic field), fixed powders, and polycrystalline bulk samples. The temperature dependence of the crystal structure parameters of some of these intermetallic compounds was determined from x-ray diffraction measurements. It was found that the temperatures of magnetic disordering of the gadolinium magnetic subsystem and the transition of the manganese subsystem from the ferromagnetic to the antiferromagnetic state decrease as the gadolinium content is decreased, so that in compositions with x<0.3 this transition is a first-order phase transition, and with further decrease of the gadolinium content it becomes second-order. In intermetallic compounds of this system with x = 0.3 and 0.4 another spontaneous first-order transition is observed at lower temperatures. In a magnetic field the magnetization of all the investigated intermetallic compounds except for the composition x=0.5 undergo a metamagnetic transition. The T-x, H-x, and H-T magnetic phase diagrams are constructed. The experimental data are interpreted with allowance for the fact that according to the results of previous studies, the Mn-Mn exchange interaction is antiferromagnetic, and thus the examined intermetallic compounds are two-sublattice ferrimagnets with negative exchange interaction in one of the sublattices. Calculations performed within the framework of this model in the Yafet-Kittel approximation, which assumes that the sublattice with negative exchange can be divided into two sub-sublattices, permit a quantitative description of the experimental results in most cases.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)