Surface magnetoelastic coupling coefficients of single-crystal fcc Co thin films

We propose a method of analysis that allows indirect determination of magnetoelastic coupling coefficients for thin magnetic films. The method is based on a general phenomenological equation describing the dependence of the effective magnetic anisotropy energy density on film thickness for a thin cubic ferromagnetic film sandwiched between two nonmagnetic layers of the same material. We show that by fitting the measured effective anisotropy energy density with this equation using independently measured elastic strain in the film and the saturation magnetization ${\mathit{M}}_{\mathit{s}}$, we can extract the Néel surface magnetic anisotropy energy density ${\mathit{K}}^{\mathit{s}}$ and either of the surface magnetoelastic coupling coefficients ${\mathit{B}}_1^{\mathit{s}}$ or ${\mathit{B}}_2^{\mathit{s}}$ depending on the film orientation. The model is applied to published data for fcc Co/Cu(111) superlattices. We find that ${\mathit{B}}_2^{\mathit{s}}$=-23.5 erg/${\mathrm{cm}}^2$ and ${\mathit{K}}^{\mathit{s}}$(Co/Cu)(111)=+0.47 erg/${\mathrm{cm}}^2$. While such large values of ${\mathit{B}}^{\mathit{s}}$ relative to ${\mathit{K}}^{\mathit{s}}$ are surprising, recent direct measurements of ${\mathit{B}}^{\mathit{s}}$ in polycrystalline Ni films show these values to be reasonable.