The distributions of atoms and magnetic moment in an antiferromagnetic γ-MnNi single crystal

The nuclear and magnetic scattering from a 73 at.% gamma -MnNi single crystal has been measured along the (100), (110) and (111) crystal directions using neutron polarisation analysis at 4.2K. The nuclear scattering is consistent with the presence of atomic short-range ordering significant only for the first few neighbours with nickel atoms tending to prefer a manganese-rich atomic environment. The magnetic scattering, due to spatial fluctuations of moments, if analysed using a superposing defect model centred on nickel atoms, indicates a defect radius of approximately 6 AA. The nickel moment is (0.1+or-0.1) mu B . Along the (100) crystal direction there is an excess contribution to the magnetic diffuse scattering which is thought to be due to static transverse moment fluctuations.