Magnetic Anisotropy and Orbilal Magnetic Moment in Ordered FePt Nanoparticles

点击翻译按钮获取中文摘要

In this study, we aimed to clarify the correlation between magnetic anisotropy and orbital moment in ordered alloys consisting of transition metal(TM; Fe or Co) and noble metal (NM; Pt or Au). Improvement in X-ray spectroscopic experiment and systematic measurement have provided the following outcomes with a comparison between nanometer-sized materials and the bulk sample(1) Experimental achievements:X-ray absorption spectroscopy has been extended to the range of high pressure up to 50 GPa. We have also succeeded in angle-resolved photoemission spectroscopy for the FePt_3 ordered alloy. These techniques are advantageous to studying the nanometer-sized materials in terms of electronic structure by a comparative analysis with the bulk sample. From X-ray magnetic circular dichroism (XMCD)at the Pt L_<2,3>-edges in CoPt thin films, the orbital component of Pt 5d states was estimated, consequently it has been revealed that the orbital moment is decreased with reducing the film thickness. To … More examine the anisotropy in the orbital component, the difference in dichroic intensity between out-of plane and in-plane geometries was also recorded. These techniques are available for understanding size effect; in particular, it is valuable to link in-situ measurement with sample preparation.(2) Scientific outcomes:For the role of NM in the ordered alloys, hybridization between NM 5d and TM 3d orbitals is important for forming the ordered structure, in consequence the spin-orbit interaction of NM 5d states is notable for the magnetic properties. For the perpendicular magnetization thin films, however, the enhancement in magnetic anisotropy constant is not directly associated with the magnitude of orbital moment, but may be ascribed to metallographic and crystallographic structures in the thin films. From the X-ray absorption experiments of Au_4Mn ordered alloy under high pressure, some discussion for Gruneisen parameter can be developed, and the magneto-volume effect should be examined on the basis of spin-fluctuation. Less