Structure and magnetic properties of SmMn2(Ge1−xSix)2

Abstract

The structure and magnetic properties of SmMn2(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. In all compounds a transition from the ferromagnetic to the antiferromagnetic state is observed at a lower temperature T1, which first decreases, goes through a minimum at x=0.4–0.6, and then increases again with Si concentration. As temperature increases, for the compounds with x<0.3 both a antiferromagnetic–ferromagnetic transition and the ferromagnetic–paramagnetic transitions are observed as well at T2 and at the Curie temperature Tc, respectively. With increasing Si content the Tc decreases, whereas T2 increases from 140 K for x=0 to 215 K for x=0.2. For compounds with x≥0.3 the antiferromagnetic–paramagnetic transition was observed with increasing temperature and the Néel temperature increases with increasing Si content. The saturation magnetization at 1.5 K decreases first, goes through a minimum at x=0.6, and then increases again with increasing Si content. At room temperature, the saturation magnetization decreases monotonically from 3.27 μB/f.u. for x=0 to nearly zero for x=0.3.