X-ray absorption spectroscopy studies of the magnetic anisotropy structure of nano-scale FePt and CrPt3 materials

• Main Authors: Yen-Heng Huang, 黃彥衡
• Other Authors: Chih-Hao Lee
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/994nk9

碩士 === 國立清華大學 === 工程與系統科學系 === 92 === ABSTRACT The author was focused on studying the advanced magnetic nano-scale materials by synchrotron X-ray absorption fine structure (XAFS) and X-ray diffraction (XRD) to understand the relationship between magnetic, atomic and electronic structure. Two different kinds of material systems in this study, namely, the CrPt3 expitaxial thin-film system, and the self-assembled FePt nanoparticles system. Both systems are the most potential materials in the future magnetic recording technologies. CrPt3 thin films exhibit perpendicular magnetic anisotropy (PMA) and large Kerr rotation angles. In order to understand the PMA effect of the CrPt3 thoroughly, the directional chemical order S and polarization-dependent XAFS were measured. The best PMA effect can be found when the plane normal order parameter is the largest while the in-plane one is still low. At the same time, Cr-Cr bond-distance is slightly distorted by XAFS analysis. This anisotropic directional long-range chemical order might be due to the anisotropic interdiffusion and the compound formation between the Cr and Pt layer. For short-range order analysis, the PMA effect might be attributed to the difference of the Cr-Cr bond-distance between plane-normal and in-plane. In the study of self-assembled FePt nanoparticles system, the superlattice structures and coalescence of self-assembled FePt nanoparticles were studied by XRD and XAFS techniques. During the annealing process, the XANES spectra (Fe K-edge) were found shifting to a higher energy as the annealing temperature increased. The shift of this iron K-edge might be attributed to the quantum size effect, surface effect or oxidation effect.