Crystal distortion and magnetic structure of γ-MnT (T=Rh, Ru) alloys

We have made X-ray and neutron diffraction experiments and magnetic susceptibility measurements for γ-MnRh alloys and γ-MnRu alloys with a small amount of Cu. The γ-Mn alloy containing 10 at % Rh at 10 K shows an orthorhombic structure with a=3.806, b=3.748 and c=3.671 A and a non-collinear antiferromagnetic structure with μa=0, μb=1.24 and μc=2.04 μB/Mn atom. The crystal transition occurs from the orthorhombic structure to the tetragonal structure with c/a<1 at To (=520 K) and finally to the cubic structure at Tt (=570 K), which is nearly equal to the Neel temperature TN. The γ-Mn alloy with 14 at % Ru and 5 at % Cu at 10 K has the similar structure with a=3.794, b=3.75 and c=3.677 A, and μa=0, μb=1.22 and μc=2.47 μB Mn atom. The crystal transition temperatures and the Neel temperature are as follows: To=380 K, Tt=500 K and TN=520 K. (author)