.3 D Metal Film Structure And Magnetic Study

Surface and ultrathin magnetism are frontier and hot topics in research field of magnetism. During the past two decades, with the development of experiment and theory, a great achievement has been made in artificial low dimensional magnetic system. The deeply understanding is not only for the interest of fundamental research, but also is the groundwork of the most exciting challenge area in nanotechnology: spintronics.In this thesis, I mainly introduce 4 works during these 5 years as PH. D. student: 1. Why Permalioy is so soft? 2. Kinetics of martensitic transformation of Fe on Cu(001). 3. LEED pattern of bcc Ni on GaAs(001). 4. The mechanism of uniaxial anisotropy in Fe on GaAs(001).1. A new Permalloy single crystalline phase with body-centered-cubic (bcc) structure has been achieved on GaAs(001) by molecular beam epitaxy. Its magnetism, Curie temperature and magnetic anisotropy are determined experimentally, and compared to those of conventional face-centered-cubic (fcc) Permalloy. Unexpectedly the vanishing magnetic cubic anisotropy in Permalloy is found to be independent of its atomic structure but depends only upon the stoichiometry of Fe and Ni in the Fe_x Ni_1-x alloy. This new observation is further investigated and confirmed by first principles electronic band calculations, which helps to understand the long-standing issue why Permalloy should be a soft magnet.2. The martensitic transformation of Fe on Cu (001) as a function of temperatures has been investigated in situ and in real time by variable temperature scanning tunnelling microscope. The result shows the whole process how the martensitic phase nucleates and evolves on the nanometer scale as the temperature decreases. It is found that the surface atomic steps together with the cooling speed play an important role in determining the kinetics of the martensitic transformation.3. The morphology of bcc Ni on GaAs(001) at different thickness is investigated by STM and LEED, and compared with bcc Fe on GaAs(001). Bcc Ni is found to be Volmer-Weber growth mode, however with small morphology roughness before 7ML, and 1×1 LEED pattern is achieved at this rigion. After that, the increasing roughness should take the response of LEED pattern disappearance.4. By comapring Fe on GaAs(001) and InAs(001) system, we find the magnetic uniaxial anisotropy origins from the magnetoelastic effects due to interface strain anisotropy, and anisotropic strain relaxation will also influence the magnetic uniaxial anisotropy.