Neutron polarisation analysis of scattering from antiferromagnetic gamma -MnCu and gamma -MnPd

The antiferromagnetic defect scattering from a 10 at.% gamma -MnCu alloy and a 10 at.% gamma -MnPd alloy has been measured at 4.2K using polarisation analysis. The magnetic defects in MnCu are largely on first neighbours, but for MnPd the disturbance is greatest on second neighbours. Within +or-0.2 mu B there appears to be no moment at the impurity site in both cases. In fitting the polycrystalline results with a cubic defect, d mu /dc=-4.3+or-0.6 mu B /at for MnCu and +3.1+or-0.3 mu B /at for MnPd have been calculated from the intensity at the (001) position. These numbers agree with the d mu /dc obtained from the variation of magnetic Bragg scattering with composition in both alloy systems. Cu atoms cluster in gamma -Mn whereas Pd atoms anticluster.