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

抄録

  Magnetic interactions in some intermetallic AM₂X₂ 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 ThCr₂Si₂-type 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')₂X₂ 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 antiparallel for the (U,Tb) and (Nd,Tb) cases and parallel for the (U,Nd) case, in accordance with the "spin-charge" concept.