Evidence for diffuse interfaces and tensile in-plane strains in evaporated Co/Pd(111) multilayers and their role in perpendicular magnetic anisotropy

Abstract

The local structure surrounding Co atoms in Co/Pd(1 1 1) multilayers, [Co x Angstrom + Pd 24 Angstrom] x 13 is investigated using polarized extended X-ray absorption fine structure(PEXAFS). The PEXAFS results show there is a considerable amount of Co-Pd alloy-like phase near interfaces, e.g., 31 at.% Co for x = 3.2 in a range extending 2.5 Angstrom on either side of the nominal Co layer. The in-plane tensile strains mainly lead to out-of-plane magnetization, combined with a much more negative value of the magnetostriction coefficient lambda(111) of the alloy phase. The alloy-like region should be considered in experiments and theories.