Spin-dependent electron momentum density in Fe3Si and Fe3Al

Circularly polarized synchrotron radiation of energy 200 keV has been used to study the spin dependent electron momentum distributions in Fe3Al and Fe 3Si single crystals at room temperature through magnetic Compton profile me asurements. The experiments were carried out for the crystallographic direc tions [100], [110] and [111] in Fe3Si, and [100] and [111] in Fe3Al. These results show that there is a more significant negative conduction electron spin polarization in both alloys than neutron data indicate and it is simil ar to that in pure iron. The overall characteristics of the experimental ma gnetic Compton profiles, as well as directional anisotropies, were found to be qualitatively similar for both compounds; however the anisotropy is hig her in the case of Fe3Si. The majority and minority spin band profiles have been extracted and show that large anisotropies are associated with the la tter. Their calculated anisotropy at low momenta was fully confirmed. The a b initio KKR calculation reproduces the Fe3Si profiles relatively well, but a 'fixed-spin moment approach' was needed in order to describe the Fe3Al s pin density momentum distribution.