Off-stoichiometry in Co2FeSi thin films sputtered from stoichiometric targets revealed by nuclear magnetic resonance
Off-stoichiometry in Co2FeSi thin films sputtered from stoichiometric targets revealed by nuclear magnetic resonance
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核磁共振揭示化学计量靶材溅射 Co2FeSi 薄膜的非化学计量
DOI：
10.1088/0022-3727/42/8/084017
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
G. Reiss
中科院分区：
文献类型：
--
作者：
S. Wurmehl;J. T. Kohlhepp;H. Swagten;B. Koopmans;C. Blum;V. Ksenofontov;H. Schneider;G. Jakob;D. Ebke;G. Reiss
Co2FeSi是一种半金属铁磁体，具有极高的磁矩和居里温度。然而，实验发现薄膜样品具有较低的隧道磁阻比、较低的自旋极化和较低的磁矩。因此，采用自旋回波核磁共振技术对不同基团的Co2FeSi薄膜进行了研究。核磁共振探测活性原子的局域超精细场，它强烈依赖于局域环境。因此，核磁共振能够揭示Co2FeSi薄膜中59Co核的下一个相邻的壳层。正如预期的那样，我们的核磁共振研究表明，主共振线对应于L21环境中的59Co核，但在主线的高频位置也有额外的共振线，相邻共振线之间的间距为32 MHz。额外的共振线对应于59Co，比预期的L21型有序的Fe相邻的更多，这被解释为通过从化学计量比的靶溅射产生的非化学计量比薄膜的形成。对核磁共振数据的分析和与非化学计量比的块体样品的比较表明，薄膜的成分约为Co2Fe(Si0.92Fe0.08)。这种非化学计量学或许可以解释观察到的偏离预期行为的现象。
Co2FeSi is predicted to be a half-metallic ferromagnet with an extraordinary high magnetic moment and Curie temperature. However, a low tunnel magneto-resistance ratio, a lower spin polarization and a lower magnetic moment were experimentally observed in thin film samples. Consequently, thin Co2FeSi films of different groups were studied using spin-echo nuclear magnetic resonance (NMR). NMR probes the local hyperfine fields of the active atoms, which strongly depend on the local environment. NMR is thus able to reveal the next neighbouring shells of the 59Co nuclei in the Co2FeSi thin films. As expected, our NMR study shows the main resonance line corresponding to 59Co nuclei in the L21 environment but also additional resonance lines at the high frequency site of the main line with a spacing between adjacent resonance lines of 32 MHz. The additional resonance lines correspond to 59Co with more Fe next neighbours than expected for the L21 type ordering, which is interpreted as the formation of an off-stoichiometric film yielded by sputtering from a stoichiometric target. The analysis of the NMR data and a comparison with off-stoichiometric bulk samples reveals the composition of the thin films to be about Co2Fe(Si0.92Fe0.08). This off-stoichiometry might explain the observed deviations from the expected behaviour.
影响因子：
3.7
作者：
Schneider, H.;Jakob, G.;Adrian, H.
通讯作者：
Adrian, H.