Magnetic Anisotropy and Orbilal Magnetic Moment in Ordered FePt Nanoparticles

在这项研究中，我们旨在阐明由过渡金属（TM； Fe或Co）和贵金属（NM； Pt或Au）组成的有序合金的磁各向异性和轨道矩之间的关系。x射线光谱实验的改进和系统测量，使得纳米材料与本体样品的对比得到以下结果：(1)实验成果：x射线吸收光谱的高压范围扩展到50 GPa。我们还成功地对FePt_3有序合金进行了角分辨光发射光谱分析。这些技术有利于通过与体样品的比较分析来研究纳米材料的电子结构。利用CoPt薄膜中Pt L_<2,3>-边缘的x射线磁圆二色性（XMCD）估计了Pt 5d态的轨道分量，结果表明，轨道矩随薄膜厚度的减小而减小。为了进一步研究轨道分量的各向异性，还记录了平面外和平面内几何形状的二向色强度差异。这些技术可用于理解尺寸效应；特别是，将原位测量与样品制备联系起来是有价值的。(2)科学成果：纳米在有序合金中的作用，纳米5d和TM 3d轨道之间的杂化对有序结构的形成至关重要，因此纳米5d态的自旋轨道相互作用对磁性能有显著影响。然而，对于垂直磁化薄膜，磁各向异性常数的增强与轨道矩的大小没有直接关系，而可能归因于薄膜中的金相和晶体结构。从Au_4Mn有序合金在高压下的x射线吸收实验中，可以对Gruneisen参数进行一些讨论，并在自旋涨落的基础上对磁体积效应进行检验。少

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