Investigation of magnetic properties of NdMn2(Ge1−xSix)2

Abstract

The structure and magnetic properties of NdMn2(Ge1−xSix)2 compounds (x=0–1.0) have been investigated. All the compounds crystallize in ThCr2Si2-type structure. Substitution of Si for Ge leads to a linear decrease of the lattice constants and the unit-cell volume. With increasing temperature, for the compounds with x⩽0.5, both spin reorientation and ferromagnetic– paramagnetic transition are observed as well at Tr and TC(Mn), respectively. The spin reorientation temperature Tr and the Curie temperature TC(Mn) decrease linearly with Si content from 215 and 339 K at x=0–40 and 306 K at x=0.5, respectively. In compounds with 0.3<x⩽0.5 the ferromagnetic component and the antiferromagnetic component may coexit. For compounds with x⩾0.6 the ferromagnetic–antiferromagnetic and the antiferromagnetic–paramagnetic transition are observed and the Curie temperature TC(Nd) decreases monotonically while the Néel temperature TN(Mn) increases monotonically with Si content. A tendentious spin phase diagram has been obtained. The saturation magnetization at 1.5 K decreases first, goes through a minimum at x=0.5, and then increases again.