Growth and magnetic properties of ultrathin Fe films on Pt(1 1 1)

Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and surface magneto-optical Kerr effect (SMOKE) were used to investigate the growth mode, alloy formation, and magnetic properties of ultrathin Fe films deposited on Pt(1 1 1) surface. The growth mode of Fe films on Pt(1 1 1) at RT is at least 3 ML layer-by-layer growth before three-dimensional island growth begins. When the thickness of Fe films was 1 ML, no Kerr signal is observed at room temperature. Both the polar and longitudinal Kerr signals can be detected when the thickness of Fe films (dFe) is 1.5 ML. When the thickness of Fe films is higher than 1.5 ML, only the longitudinal Kerr signal can be observed. The easy axis of the magnetization is in the in-plane direction when dFe > 1.5 ML. After the formation of Fe–Pt surface alloy for 5 ML Fe ultrathin films on a flat Pt(1 1 1) surface, the Kerr signal and the coercivity enhance to 150% and 1100%, respectively. The formation of Fe–Pt surface alloy was confirmed by AES. The evolutions of the magnetic properties are strongly relative to the diffusion process of Fe thin films into Pt substrate.