Chemical effects at metal/oxide interfaces studied by x-ray-absorption spectroscopy
Chemical effects at metal/oxide interfaces studied by x-ray-absorption spectroscopy
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DOI：
10.1103/physrevb.64.214422
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发表时间：
2001-11
影响因子：
3.7
通讯作者：
T. J. Regan;H. Ohldag;C. Stamm;F. Nolting;J. Lüning;J. Stöhr;R. White
中科院分区：
文献类型：
--
作者：
T. J. Regan;H. Ohldag;C. Stamm;F. Nolting;J. Lüning;J. Stöhr;R. White
铁磁/反铁磁界面的化学和磁性表征对于理解交换各向异性和其他磁性现象的微观起源至关重要。我们使用高分辨率L边X射线吸收光谱（XAS）来研究反铁磁氧化物与铁磁金属的界面，该光谱具有元素特异性且对化学环境和自旋取向敏感。在生长的金属/氧化物界面的氧化/还原反应的明确的定量证据。用高分辨XAS研究了氧化物（5- 30 AA{}）/金属（1- 10 AA{}）形式的原位和非原位生长样品，其中氧化物为NiO或CoO，金属为Fe、Co或Ni。对于所有样品，与氧化物（金属）层相邻的金属（氧化物）层被部分氧化（还原）。光谱的定量分析表明，在界面两侧的一到两个原子层被氧化/还原。元素系列样品显示氧化/还原的量与相邻阳离子的氧化电位差雅阁，例如，铁金属层比钴或镍金属层更强烈地还原氧化物层。退火到通常用于偏置器件的温度，显示出显着增加氧化/还原的量。铁的氧化行为被证明取决于可用的氧的量。我们的研究结果被认为是交换各向异性的理解提供了重要的信息。
A chemical and magnetic characterization of ferromagnet/antiferromagnet interfaces is essential to understand the microscopic origins of exchange anisotropy and other magnetic phenomena. We have used high-resolution L-edge x-ray absorption spectroscopy (XAS), which is element specific and sensitive to chemical environment and spin orientation, to investigate the interface of antiferromagnetic oxides with ferromagnetic metals. Clear quantitative evidence of oxidation/reduction reactions at the as-grown metal/oxide interface is presented. In situ-- and ex situ--grown samples of the form oxide $(5--30 \AA{})/\mathrm{metal}$ $(1--10 \AA{}),$ where oxide is either NiO or CoO and metal is either Fe, Co, or Ni, were studied by high-resolution XAS. For all samples, a metal(oxide) layer adjacent to an oxide(metal) layer was partially oxidized(reduced). Quantitative analysis of the spectra showed that one to two atomic layers on either side of the interface were oxidized/reduced. An elemental series of samples showed that the amount of oxidation/reduction was in accord with the difference in oxidation potentials of the adjacent cations, e.g., oxide layers were more strongly reduced by an iron metal layer than by cobalt or nickel metal layers. Annealing to temperatures, typically used to bias devices, was shown to significantly increase the amount of oxidation/reduction. The oxidation behavior of iron was shown to depend on the amount of oxygen available. Our results are believed to provide important information for the improved understanding of exchange anisotropy.