STRAIN-INDUCED PERPENDICULAR MAGNETIC-ANISOTROPY IN ULTRATHIN NI FILMS ON CU3AU(001)

We have investigated magnetism, morphology and structure of nickel fil ms grown on Cu3Au(0 0 1) to explore the potential of modifying magneti c anisotropies by epitaxial strains. Ultrathin films from the submonol ayer region up to 55 monolayers (ML) were grown epitaxially on a Cu3Au (0 0 1) single crystal. Layer-by-layer growth is observed up to 10 ML. A quantitative analysis of the low-energy electron diffraction (LEED) pattern reveals coherent film growth up to 5 ML. Between 5 and 8 ML t he in-plane lattice constant is reduced by 4%, which corresponds to a reduction of the film strain by 70%. This is accompanied by an increas e in the interlayer spacing, which is in quantitative agreement with p redictions of linear elasticity theory. Kerr measurements show that th e films have an in-plane magnetization in the thickness region from 3 to 5 ML and for thicknesses larger than 12 ML, Between 5 and 12 ML a p erpendicular anisotropy is observed which is particularly pronounced b etween 8 and 10 ML. This reorientation of the magnetization direction is caused by the coherency strain in the film.