Structural origin of magnetic anisotropy in Co-Pt alloy films probed by polarized XAFS

Polarized X-ray absorption fine structure (XAFS) measurements at the Co K a nd Pt L-3 edges show that the perpendicular magnetic anisotropy found in ep itaxial fee CoPt3 (111) films stems from the existence of anisotropic local ordering. Such ordering, induced during the codeposition process and depen dent on the growth temperature, is characterized by preferential CoCo pairs in time film plane, balanced by preferential CoPt pairs out of the planet resulting from some Co 2D-segregation. Polarized XAFS at the Pt edge reveal s similar anisotropic local ordering in epitaxial hcp Co3Pt (0001) films ex hihiting a larger magnetocrystalline anisotropy compared to that of bulk hc p Co. Besides, a polarization dependence of the Co XANES profile is observe d only for the Co3Pt films exhibiting hcp symmetry.