Perpendicular magnetic anisotropy of multilayers: recent insights

Extending our understanding of perpendicular magnetic anisotropy (PMA) beyond the phenomenological approach of volume (K_V) and interface anisotropies (K_S) requires caution. Experimentally, many factors such as roughness, formation of interface alloys, or patchiness of ultrathin layers may cause a reduction in PMA. Where stresses are present in multilayer growth, these may, under particular circumstances, contribute to both K_V and K_S, as demonstrated for the Cu/Ni/Cu system. Theoretically, the difficulty in modelling incoherently grown materials prevents a detailed quantitative comparison with most experimental systems, so that an evaluation of the underlying approximations common to all of the quantitative theoretical studies becomes very difficult.