  Highly (001) oriented thin films of Co2MnSi have been grown on lattice
matched GaAs(001) without a buffer layer. Stoichiometric films exhibited a
saturation magnetization slightly reduced from the bulk value and films grown
at the highest substrate temperature of 689 K showed the lowest resistivity (33
micro.ohm.cm at 4.2 K) and the lowest coercivity (14 Oe). The spin polarization
of the transport current was found to be of the order of 55% as determined by
point contact Andreev reflection spectroscopy. The reduced magnetization
obtained was attributed to the antiferromagnetic Mn2As phase. Twofold in-plane
magnetic anisotropy was observed due to the inequivalence of the <110>
directions, and this was attributed to the nature of the bonding at the
reconstructed GaAs surface.
