Spin-dependent electron momentum densities in Cu2MnAl studied by Compton scattering

The spin density in the Heusler alloy Cu2MnAl, has been studied in a Compton scattering experiment with 92 keV circularly polarized synchrotron radiation on the high-energy beamline at ESRF. The conduction electrons were found to have a negative spin polarization of 0:4 B which is at variance with the deduction of a positive moment from earlier neutron data; neither was any evidence found for a 3d spin moment on the copper site. The spin moment on the Mn site at room temperature was determined as 3:25 B, which is in agreement with neutron data. The spin-dependent Compton profiles for the [100], [110] and [111] directions, reported here, show anisotropy in the momentum density which is in good agreement with new KKR calculations based on a ferromagnetic ground state. By combining charge- and spin-dependent Compton data the momentum space anisotropies in the majority and minority bands have been analysed. Both the majority and minority spin densities are anisotropic.