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Percolative Ferromagnetism in Anatase Co:TiO2

S. R. Shinde·S. B. Ogale·Abhijit S. Ogale·S. J. Welz·A. Lussier·Darshan C. Kundaliya·H. Zheng·S. Dhar·M. S. R. Rao·R. Ramesh·Y. U. Idzerda·N. D. Browning·T. Venkatesan
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Abstract

We revisit the most widely investigated and controversial oxide diluted magnetic semiconductor (DMS), Co:TiO2, with a new high temperature film growth, and show that the corresponding material is not only an intrinsic DMS ferromagnet, but also supports a percolative mechanism of ferromagnetism. We establish the uniformity of dopant distribution across the film cross section by Z-contrast imaging via scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) at spatial resolution of 0.4 nm and the oxidized 2+ valence state of cobalt by x-ray absorption spectroscopy (XAS). The dependence of magnetic properties on cobalt concentration is consistent with the defect polaron percolation model. The peculiar increase in the transport activation energy above a specific cobalt concentration further emphasizes the polaron contribution to magnetic order.

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S. R. Shinde, S. B. Ogale, Abhijit S. Ogale, S. J. Welz, A. Lussier, Darshan C. Kundaliya, H. Zheng, S. Dhar, M. S. R. Rao, R. Ramesh, Y. U. Idzerda, N. D. Browning, T. Venkatesan. 2005-05-10. Percolative Ferromagnetism in Anatase Co:TiO2. https://arxiv.org/abs/cond-mat/0505265

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