Magnetic anisotropy and reorientation in Co/Rh superlattices

Co/Rh multilayers have been grown at different substrate temperatures in UHV by molecular beam epitaxy (MBE). The Co thickness ranges between 3 and 9 Å, while the Rh thickness is fixed at 9 W. In situ RHEED and X-ray diffraction measurements reveal an epitaxial growth of these films on the fcc (111) Rh buffer layer. From polar hysteresis loop measurements we find that a magnetic reorientation from a perpendicular to in-plane direction occurs in these films at around 4 Co-layers at room temperature, and at around 2 Co-layers at 456 K. From our measurements we estimate the second order volume anisotropy K_V ≈10⁷ erg/cm³, and the surface anisotropy K_S≈0.3 erg/cm² at room temperature. The nature of the magnetic reorientation is discussed. As far as we know this is the first report on the existence of the magnetic reorientation phenomenon in Co/Rh superlattices as a function of film thickness and temperature