First Principle Calculation of the Magnetocrystalline Anisotropy Energy of FePt and CoPt Ordered Alloys

The spin-polarized band calculations including spin-orbit interaction for L1 0 -FePt and CoPt ordered alloys have been performed with LMTO-ASA method in the frame of local spin density functional approximation. It has been shown that strong uniaxial magnetic anisotropy of both alloys is brought about by a large spin-orbit coupling of Pt atom and a strong hybridization of Pt d bands with highly polarized Fe (Co) d bands. The obtained magnetocrystalline anisotropy energy (MAE) is about 16×10 6 J/m 3 for FePt and 9×10 6 J/m 3 for CoPt. It is also found that both MAE's have a trend of increase with increasing axial ratio c / a in the vicinity of measured c / a . This can be regarded as being associated with the behavior that the MAE's decrease with increasing band filling.