Magnetic Anisotropy and Orbilal Magnetic Moment in Ordered FePt Nanoparticles

在这项研究中，我们的目的是澄清磁各向异性和轨道矩之间的相关性，在有序合金组成的过渡金属（TM; Fe或Co）和贵金属（NM; Pt或Au）。通过对X射线吸收光谱实验的改进和系统测量，将纳米材料与体样品进行了比较，取得了以下成果：（1）实验成果：将X射线吸收光谱的测量范围扩展到了50 GPa的高压范围。我们还成功地对FePt_3有序合金进行了角分辨光电子能谱分析。这些技术有利于通过与体样品的对比分析来研究纳米材料的电子结构。从CoPt薄膜中Pt L <2，3>边的X射线磁圆二色性（XMCD），估算了Pt 5d态的轨道分量，从而揭示了随着薄膜厚度的减小，Pt 5d态的轨道矩减小。到 关于我们 检查轨道分量中的各向异性，还记录了面外和面内几何形状之间的二向色性强度的差异。这些技术对于理解尺寸效应是有用的，特别是将原位测量与样品制备相结合是有价值的。(2)科学成果：对于NM在有序合金中的作用，NM 5d和TM 3d轨道之间的杂化对于形成有序结构是重要的，因此NM 5d状态的自旋-轨道相互作用对于磁性是显著的。对于垂直磁化薄膜，磁各向异性常数的增加与轨道矩的大小没有直接关系，而可能与薄膜的金属结构和晶体结构有关。从高压下Au_4Mn有序合金的X射线吸收实验中，可以对Gruneisen参数进行一些讨论，并从自旋涨落的角度考察磁体积效应。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