Crystal distortion and magnetic structure of ?-MnPt alloys

We have made X-ray and neutron-diffraction experiments and magnetic susceptibility measurements for γ-MnPtalloys. The alloy containing 8 at. % Pt shows a face-centered orthorhombic structure with a=3.807, b=3.748 and c=3.685 A and a non-collinear antiferromagnetic structure with μa=0, μb=1.27 and μc=2.001 μB/Mn atom at 10 K. The crystal transition occurs from the orthorhombic structure to a tetragonal structure with c/a 1 and μ=2.58 μB/Mn atom at 10 K, and transforms to a cubic structure at 325 K, which is lower than the Neel temperature (=500 K). We have determined a phase diagram for γ-MnPtalloys containing 7–20 at. % Pt.