Structural and Magnetic Properties of Ultrathin Fe Films on Pt(001) Surface

Magnetic anisotropy evolution of ultrathin Fe films grown on Pt(001) single-crystal surface is investigated by UHV in situ surface magneto-optical Kerr effect (SMOKE) measurement. After annealing at ～600K, the magnetic anisotropy of Fe film switches from in-plane to perpendicular at low coverage, leading to a spin reorientation transition (SRT). Meanwhile, in the range of 3--4 monolayer (ML) thickness, the coercivity of the Fe polar hysteresis loop decreases dramatically. Further scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED) investigation correlates the magnetic properties with the film structures. We attribute this SRT to the formation of Fe--Pt ordered alloy.