Strain-and overlayer-induced in-plane magnetocrystalline anisotropy: First-principles determination for fcc (110) Co thin films

The in-plane interface magnetocrystalline anisotropy (MCA) of fee Co (110), either as a free standing monolayer or as an overlayer on a Cu substrate, is investigated using the local density all-electron full-potential linearized augmented plane-wave method. We find an in-plane MCA which has the same order of magnitude as the perpendicular MCA, and which exhibits a significant twofold anisotropy. The results for free standing monolayers calculated with different lattice constants reveal that (i) the strength of the in-plane MCA is severely changed by the strain - introducing an 8% strain (relative to the Cu lattice constant) induces a five times larger in-plane MCA - and (ii) the change of band structure due to the strain plays an important role in determining the in-plane MCA. The strength of the in-plane MCA is found to be largely enhanced by the nonmagnetic Cu substrate while it is reduced by the structural relaxation. Interestingly, for all systems the in-plane easy axis is found to lie along [110], which is along the direction of the in-plane nearest neighbor atom.