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arXiv · 1008.1908

Nanoscale Dichotomy of Ti 3d Carriers Mediating the Ferromagnetism in Co:TiO2 Anatase Thin Films

T. Ohtsuki·A. Chainani·R. Eguchi·M. Matsunami·Y. Takata·M. Taguchi·Y. Nishino·K. Tamasaku·M. Yabashi·T. Ishikawa·M. Oura·Y. Senba·H. Ohashi·S. Shin
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Abstract

We study the surface and bulk electronic structure of the room-temperature ferromagnet Co:TiO2 anatase films using soft and hard x-ray photoemission spectroscopy with probe sensitivities of ~1 nm and ~10 nm, respectively. We obtain direct evidence of metallic Ti$^{3+}$ states in the bulk, which get suppressed to give a surface semiconductor, thus indicating a surface-bulk dichotomy. X-ray absorption and high-sensitivity resonant photoemission spectroscopy reveal Ti$^{3+}$ electrons at the Fermi level (E$_F$) and high-spin Co$^{2+}$ electrons occurring away from E$_F$. The results show the importance of the charge neutrality condition: Co$^{2+}$ + V$_{O}$$^{2-}$ + 2Ti$^{4+}$ $\leftrightarrow$ Co$^{2+}$ + 2Ti$^{3+}$ (V$_O$ is oxygen vacancy), which gives rise to the elusive Ti 3d carriers mediating ferromagnetism via the Co 3d-O 2p-Ti 3d exchange interaction pathway of the occupied orbitals.

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T. Ohtsuki, A. Chainani, R. Eguchi, M. Matsunami, Y. Takata, M. Taguchi, Y. Nishino, K. Tamasaku, M. Yabashi, T. Ishikawa, M. Oura, Y. Senba, H. Ohashi, S. Shin. 2010-08-11. Nanoscale Dichotomy of Ti 3d Carriers Mediating the Ferromagnetism in Co:TiO2 Anatase Thin Films. https://doi.org/10.1103/physrevlett.106.047602

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