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arXiv · 1504.02392

Electronic and magnetic properties of off-stoichiometric Co$_\mathrm{2}$Mn$_β$Si/MgO interfaces studied by x-ray magnetic circular dichroism

V. R. Singh·V. K. Verma·K. Ishigami·G. Shibata·A. Fujimori·T. Koide·Y. Miura·M. Shirai·T. Ishikawa·G. f. Li·M. Yamamoto
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Abstract

We have studied the electronic and magnetic states of Co and Mn atoms at the interface of the Co$_\mathrm{2}$Mn$_β$Si (CMS)/MgO ($β$=0.69, 0.99, 1.15 and 1.29) magnetic tunnel junction (MTJ) by means of x-ray magnetic circular dichroism. In particular, the Mn composition ($β$) dependences of the Mn and Co magnetic moments were investigated. The experimental spin magnetic moments of Mn, $m_\mathrm{spin}$(Mn), derived from XMCD weakly decreased with increasing Mn composition $β$ in going from Mn-deficient to Mn-rich CMS films. This behavior was explained by first-principles calculations based on the antisite-based site-specific formula unit (SSFU) composition model, which assumes the formation of only antisite defect, not vacancies, to accommodate off-stoichiometry. Furthermore, the experimental spin magnetic moments of Co, $m_\mathrm{spin}$(Co), also weakly decreased with increasing Mn composition. This behavior was consistently explained by the antisite-based SSFU model, in particular, by the decrease in the concentration of Co$_\mathrm{Mn}$ antisites detrimental to the half-metallicity of CMS with increasing $β$. This finding is consistent with the higher TMR ratios which have been observed for CMS/MgO/CMS MTJs with Mn-rich CMS electrodes.

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V. R. Singh, V. K. Verma, K. Ishigami, G. Shibata, A. Fujimori, T. Koide, Y. Miura, M. Shirai, T. Ishikawa, G. f. Li, M. Yamamoto. 2015-04-09. Electronic and magnetic properties of off-stoichiometric Co$_\mathrm{2}$Mn$_β$Si/MgO interfaces studied by x-ray magnetic circular dichroism. https://doi.org/10.1063/1.4921538

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