First-principles investigations of the magnetocrystalline anisotropy in strained fcc Co

First-principles calculations have been performed to evaluate the magnetocr ystalline anisotropy energy as well as the phenomenologically defined aniso tropy and magnetoelastic constants of strained fee Co. We considered an app lied uniaxial strain along both the [110] and [001] directions. It is found that the uniaxial strains not only induce large uniaxial and planar magnet oelastic anisotropies but also can act to suppress the cubic magnetocrystal line anisotropy. In the cubic limit, the calculated magnetoelastic coupling constant B-1 and magnetocrystalline anisotropy constant K-1 agree well wit h current experiments. The results are used to discuss the interesting beha vior of the magnetic anisotropies as a function of film thickness observed recently in fcc Co(110)/Cu films. In particular, it is demonstrated that in the thick Co films (greater than or equal to 50 Angstrom) the uniaxial and in-plane anisotropies are predominantly strain induced. It is also argued that the observed abrupt transformation in the anisotropy constants at 50 A ngstrom film thickness may be caused by the combined effects of the dramati c change from the isotropic in-plane strains to the anisotropic ones and th e increase in the strain size as the film thickness is gradually reduced. [ S0163-1829(99)07621-3].