{\it In Situ} spin-reorientation transition study using surface magneto-optical Kerr effects (SMOKE)

Abstract

An in situ three-configurational surface magneto-optical Kerr effect (SMOKE) system has been developed to study ultrathin film magnetism under ultrahigh vacuum (UHV) condition. Main feature of this system is the simultaneous measurements of Kerr rotations and Kerr ellipticities in the `polar``, longitudinal``, and `transverse`` geometries at the position where deposition is carried out in a UHV growth chamber. It enables in situ three-dimensional (3D) vectorial studies of ultrathin film magnetism with a submonolayer sensitivity. We have also developed a novel method to determine all the components of magnetization vector in ultrathin ferromagnetic films using magneto-optical Kerr effects of either both p- and s-polarization waves or each polarization wave. This technique has been applied to in situ study of magnetization reversal and spin-reorientation transition (SRT) in ultrathin Co films grown on Pt(111) and Pd(111) single-crystal substrates. We observed contrasting vectorial magnetization reversal behavior dependent on the direction of magnetic easy axis. In particular, for 5.25 ML of Co, a slightly canted magnetization vector from the film normal rotates via a spiral motion in the film plane under an applied magnetic field normal to the film plane, which could be explained by an existence of in-plane anisotropy and a small tilt of an applied field. A relation between growth structures or morphology and magnetic properties of Co ultrathin films on Pd(111) surface are studied with a UHV scanning tunneling microscope (STM) and SMOKE measurement as a function of Co thickness. At the beginning of growth, the STM image of I ML Co shows almost complete monolayer coverage instead of disconnected islands. STM images of Co-covered surface reveal that the growth proceeds as a good layer-by-layer epitaxy up to a thickness of 2 ML. At higher coverages, the surface of the film shows uniformly distributed 3D clusters of `` 5 nm size manifesting 3D-like growth mode, which...