Spin and orbital magnetism in full Heusler alloys:: A density functional theory study of Co2YZ (Y = Mn,Fe; Z = Al,Si,Ga,Ge)

The effect of spin-orbit coupling and orbital polarization (OP) corrections on the spin and orbital magnetism of full Heusler alloys is investigated by means of local spin-density calculations. It is demonstrated that OP corrections are needed to explain the experimental orbital moments M-l. Model calculations employing one ligand field parameter yield the correct order of magnitude of M-l, but do not account for its quantitative composition dependence. Spin-orbit coupling reduces the degree of spin polarization of the density of states at Fermi level by a few percent. We provide arguments that Co2MnGa and the Co(2)YZ compounds with Y=Fe might not be half metals as suggested by recent experiments for Z=Si.