Imaging Spin Reorientation Transitions in Consecutive Atomic Co layers
  By means of spin-polarized low-energy electron microscopy (SPLEEM) we show that the magnetic easy-axis of one to three atomic-layer thick cobalt films on ruthenium crystals changes its orientation twice during deposition: one-monolayer and three-monolayer thick films are magnetized in-plane, while two-monolayer films are magnetized out-of-plane, with a Curie temperature well above room temperature. Fully-relativistic calculations based on the Screened Korringa-Kohn-Rostoker (SKKR) method demonstrate that only for two-monolayer cobalt films the interplay between strain, surface and interface effects leads to perpendicular magnetization. 
Farid El Gabaly (1), Silvia Gallego (2), Carmen Munoz (2), Laszlo   Szunyogh (3), Peter Weinberger (4), Christof Klein (5), ...