Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films. In this paper, Co films with different thickness of Co Si2 buffer layers were grown on Si（001） substrates. In order to investigate morphology, structure,and magnetic properties of films, scanning tunneling microscope（STM）, low energy electron diffraction（LEED）, high resolution transmission electron microscopy（HRTEM）, and surface magneto-optical Kerr effect（SMOKE） were used. The results show that the crystal quality and magnetic anisotropies of the Co films are strongly affected by the thickness of Co Si2 buffer layers. Few Co Si2 monolayers can prevent the interdiffusion of Si substrate and Co film and enhance the Co film quality. Furthermore, the in-plane magnetic anisotropy of Co film with optimal buffer layer shows four-fold symmetry and exhibits the two-jumps of magnetization reversal process, which is the typical phenomenon in cubic（001） films.
The magnetization reversal process of Fe/MgO （001） thin film is investigated by combining transverse and longi- tudinal hysteresis loops. Owing to the competition between domain wall pinning energy and weak uniaxial magnetic anisotropy, the typical magnetization reversal process of Fe ultrathin film can take place via either an ＂l-jump＂ process near the easy axis, or a ＂2-jump＂ process near the hard axis, depending on the applied field orientation. Besides, the hysteresis loop presents strong asymmetry resulting from the variation of the detected light intensity due to the quadratic magneto-optic effect. Furthermore, we modify the detectable light intensity formula and simulate the hysteresis loops of the Kerr signal. The results show that they are in good agreement with the experimental data.
We report a facile method to synthesize dispersed Fe_3O_4@C nanoparticles(NPs). Fe_3O_4 NPs were firstly prepared via the high temperature diol thermal decomposition method. Fe_3O_4@C NPs were fabricated using glucose as a carbon source by hydrothermal process. The obtained products were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), vibrating sample magnetometer(VSM) and Raman spectra. The results indicate that the original shapes and magnetic property of Fe_3O_4 NPs can be well preserved. The magnetic particles are well dispersed in the carbon matrix. This strategy would provide an efficient approach for existing applications in Li-ion batteries and drug delivery. Meanwhile, it offers the raw materials to assemble future functional nanometer and micrometer superstructures.
A planar Hall effect（PHE） is introduced to investigate the magnetization reversal process in single-crystalline iron film grown on a Si（001） substrate.Owing to the domain structure of iron film and the characteristics of PHE,the magnetization switches sharply in an angular range of the external field for two steps of 90° domain wall displacement and one step of 180°domain wall displacement near the easy axis,respectively.However,the magnetization reversal process near the hard axis is completed by only one step of 90° domain wall displacement and then rotates coherently.The magnetization reversal process mechanism near the hard axis seems to be a combination of coherent rotation and domain wall displacement.Furthermore,the domain wall pinning energy and uniaxial magnetic anisotropy energy can also be derived from the PHE measurement.
