Crystal Distortion and Magnetic Structure of γ-MnM (M = Fe, Cu, Zn) Alloys

Abstract

We conducted X-ray and neutron diffraction experiments and magnetic susceptibility measurements for γ-MnFe alloys with a small amount of Cu or Pt, and for γ-MnCu and γ-MnZn alloys. γ-(Mn_1−xFe_x)_0.95Cu_0.05 alloy with x=0.26 around 10 K shows a face-centered orthorhombic structure with a=0.3681, b=0.3655 and c=0.3622 nm, and a non-collinear antiferromagnetic structure with μ_a=0 and μ_b⁄μ_c=0.62. With increasing temperature, orthorhombic-tetragonal with c⁄a>1 structural transition occurs at T_o (=125 K) and the tetragonal structure finally transforms to a cubic structure at T_t (=352 K), which is lower than the Néel temperature T_N (=440 K). The γ-(Mn_1−xFe_x)_0.95Pt_0.05 alloy with x=0.13 at 10 K also shows a similar structure with a=0.3745, b=0.3714 and c=0.3649 nm, which has a non-collinear antiferromagnetic structure with μ_a=0, μ_b=1.03 and μ_c=1.94μ_b/(Mn or Fe) atom. The γ-Mn_1−xCu_x alloy with x≤0.26 and γ-Mn_1−xZn_x alloy with x≤0.28 show a tetragonal structure with c⁄a<1 at low temperature.