First-principles Study on the Half-metallicity and Magnetism of the (001) Surfaces of (AlP)(1)/(CrP)(1) Superlattice

The half-metallicity and magnetism of the (001) surfaces of (AlP)(1)/(CrP)(1) superlattice were investigated by means of FLAPW (Fullpotential Liniarized Augmented Plane Wave) method. We considered four types of (001) surface termination, i.e., Al(S)-, Cr(S)-, P(S) Al(S-1)-and P(S) Cr(S-1)-term systems. We found that only Cr(S)-term system maintains the half-metallicity at the surface as only this system has the calculated magnetic moment of integer number of bohr magnetons. The magnetic moment of Cr(S) atom in the system was 3.02 mu(B) which was increased from the bulk value by the effects of band narrowing and increased spin-splitting at the surface. The electronic density of states of the P(S) atom in the P(S) Al(S-1)-term showed very sharp surface states due to the broken p(z) bonds at the surface. We found there is still a strong p-d hybridization between the P(S) and Cr(S-1) layers in the P(S) Cr(S-1)-term which causes a considerable increase of magnetic moment of P(S) atom.