Evolution of magnetic hardness in the HfFe 6Ge 6-type RMn 6Sn 6− xGa x and RMn 6Sn 6− xIn x compounds (R=Tb, Dy; 0.2≤ x≤1.4)

Abstract

The HfFe 6Ge 6-type RMn 6Sn 6− x X x ′ solid solutions (R=Tb, Dy, X′=Ga, In; x≤1.4) have been studied by powder magnetization measurements. All the series are characterized by ferrimagnetic ordering and by a decrease in Curie temperatures with the substitution (Δ T c/Δ x≈−39 K for X′=Ga and Δ T c/Δ x≈−75 K for X′=In). The RMn 6Sn 6− x Ga x systems are characterized by a strong decrease in the spin reorientation temperature with substitution (Δ T t/Δ x≈−191 K and −78 K for R=Tb and Dy, respectively) while this transition almost does not change in systems containing indium. The coercive fields drastically decrease with the substitution in the TbMn 6Sn 6− x Ga x system while the substitution of In for Sn has a weaker effect. The coercive fields of the Dy compounds do not vary greatly with the substitution in both series. The behaviour of the TbMn 6Sn 6− x Ga x is compared with the evolutions observed in the TmMn 6Sn 6− x Ga x series. This comparison strongly suggests that the replacement of Sn by Ga changes the sign of the A 0 2 crystal field parameter.