| Recently, research of magnetic ultrathin film was more and more attractive because of the emergence and development of spintronics. Since the surface and interface of thin films playing a key role to influent the magnetic property of thin films and performance of spintronics devices, the study related to the surface and interface of thin films is an important way to understand the thin films magnetic property or improve the spintronics device performance. In this thesis, five topics related to interface of ultrathin film are introduced. It mainly contains quantitatively study of magnetic anisotropy in magnetic thin films, spin structure of magnetic stripe domain and evolution of magnetic stripe domain in perpendicular magnetic field.(1) The in-plane magnetic anisotropy in Fe films grown on GaAs(001) was investigated quantitatively by the magneto-optic Kerr effect with a rotating magnetic field (ROT-MOKE). The clear 1/dFe relation of the uniaxial magnetic anisotropy indicates a surprising volume contribution with easy axis along the GaAs [110] direction. Such volume anisotropy was found to be sensitive to the growth temperature and also strongly correlate with the interface anisotropy. Our results may introduce a new aspect for further understanding the origin of uniaxial magnetic anisotropy in Fe/GaAs(001) system.(2) The in-plane magnetic anisotropy in the Fe/MgO/GaAs(001) system has been carefully studied as a function of MgO thickness. The epitaxial relation is Fe(001)[110]//MgO(001)[100]//GaAs(001)[100] for dMgO>lmonolayer (ML). The interfacial uniaxial anisotropy was greatly reduced by the MgO interlayer, and the easy axis of the fourfold anisotropy was found to rotate from the GaAs(100) direction to the GaAs(110) direction. Such anisotropy transition happens within the 1.2ML MgO thickness range.(3) Single crystalline FeMn/Co bilayers were grown epitaxially on Cu(001) and investigated by magneto-optic Kerr effect (MOKE). By doing the MOKE measurement within a rotating magnetic field, we were able to retrieve quantitatively the anisotropy constant of the ferromagnetic Co layer. We show unambiguously that as the FeMn layer changes from paramagnetic (PM) to antiferromagnetic (AFM) states, it enhances the interfacial magnetic anisotropy at the FeMn/Co interface by an order of magnitude. A thickness dependent study of the magnetic anisotropy constantrevealed that this induced magnetic anisotropy may originate from the FeMn/Co interfacial spin frustration, and was determined to be 0.118 erg/cm2.(4) By using spin-polarized low-energy electron microscopy(SPLEEM), we show the first real-space observation of magnetic cycloidal chiral order in magnetic stripe domain at room temperature. Moreover, the chirality of magnetic chiral order could be controlled by reversing Fe/Ni interface. A Monte-Carlo (MC) simulation indicates that Dzyaloshinskii-Moriya interaction (DMI) is a possible origin of the chirality. The helical chiral order, spin structure of magnetic bubble domain and canted spin in stripe domain were also introduced.(5) The evolution of magnetic stripe domain with different stripe width in perpendicular magnetic field was carefully investigated by spin-polarized low-energy electron microscopy. We found the stripe width of stripe domain with opposite direction from magnetic field decreases with increasing magnetic field at small magnetic field, then the stripe domain will vanish one by one in large magnetic field and become single domain finally, and stripe width is almost a constant at large magnetic field. A linear relation was found between stripe width in zero field and large field. Saturate field fitted from fraction area in small magnetic field is more or less consistent with experiment saturate field. An universal behavior between fraction area and magnetic field multiplied by stripe width in zero field was found. |
PDF Full Text Request