Studies of Magnetic Interactions in Some Intermetallic AM₂X₂ Compounds and Their Solid Solutions

Abstract

-Magnetic interactions in some intermetallic AM 2 X 2 compounds and their solid solutions have been investigated using ac-susceptibility and neutron-diffraction measurements. The materials studied (A = U, Nd, Tb; M = Co, Ni, Cu; X = Si, Ge) have predominantly the tetragonal ThCr2Sirtype crystal structure, and ordered magnetic moments are found only on the A site aligned along the tetragonal axis in ferromagnetic basal planes. The magnetic phase diagrams of the U(M,M')zX2 solid solutions have been determined. The results suggest RKKY -like magnetic interactions in these systems, with variable magnetic structure and oscillatory behaviour of the ordering and paramagnetic Curie temperatures. The relative orientation of ordered A and Ln magnetic moments in the (A,Ln)Co2Ge2 solid solutions have been determined. It is anti parallel for the (U,Tb) and (Nd,Tb) cases and parallel for the (U,Nd) case, in accordance with the "spin-charge" concept.