Magnetic states of Mn and Co atoms at Co2MnGe/MgO interfaces seen via soft x-ray magnetic circular dichroism
Magnetic states of Mn and Co atoms at Co2MnGe/MgO interfaces seen via soft x-ray magnetic circular dichroism
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DOI：
10.1103/physrevb.82.184419
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发表时间：
2010-11-15
影响因子：
3.7
通讯作者：
Yamamoto, M.
中科院分区：
文献类型：
--
作者：
Asakura, D.;Koide, T.;Yamamoto, M.
利用软x射线磁圆二色性（XMCD）研究了富Co Co2MnGe Heusler合金薄膜中Mn和Co原子的磁态。特别研究了Co2MnGe薄膜厚度对Mn和Co磁矩的依赖关系。当Co2MnGe膜厚度减小到1-2层时，Mn的自旋磁矩减小，且与厚度大于4 ML的样品相比，MnO中Mn的L-2、l -3边缘x射线吸收光谱（XAS）显示出类似Mn2+的多晶结构，说明1和2 ML样品的Mn原子被氧化。随着厚度的减小，Co自旋磁矩略有增加。在所有的Co L-2、l -3边缘XAS和XMCD中均未观察到CoO中类似Co2+的多重结构，这表明即使在超薄样品中，Co原子也没有被氧化，并且自旋极化比较厚样品中更强。Co自旋磁矩为1.40-1.77 mu(B)，比理想化学量Co2MnGe的理论值（类似于1 mu(B)）大，富Co的薄膜成分意味着Co对位的存在会降低自旋极化。
The magnetic states of Mn and Co atoms in Co-rich Co2MnGe Heusler alloy thin films facing an MgO barrier were studied by means of soft x-ray magnetic circular dichroism (XMCD). In particular, the Co2MnGe film-thickness dependence of the Mn and Co magnetic moments was investigated. With a decrease in the Co2MnGe film thickness to 1-2 monolayers (MLs), the spin magnetic moment of Mn decreased and the Mn L-2,L-3-edge x-ray absorption spectra (XAS) showed a Mn2+-like multiplet structure in MnO, in contrast to samples thicker than 4 ML, indicating that the Mn atoms of the 1 and 2 ML samples were oxidized. The Co spin magnetic moment increased slightly with decreasing thickness. A Co2+-like multiplet structure in CoO was not observed in all the Co L-2,L-3-edge XAS and XMCD, indicating that, even in the ultrathin samples, the Co atoms were not oxidized, and were more strongly spin polarized than those in the thicker samples. Co spin magnetic moments of 1.40-1.77 mu(B) larger than the theoretical value for ideal stoichiometric Co2MnGe (similar to 1 mu(B)) and the Co-rich film composition imply the presence of Co antisites that would lower the spin polarization.