Co-occurrence of Superparamagnetism and Anomalous Hall Effect in Highly Reduced Cobalt-Doped Rutile ${\mathrm{TiO}}_{2\ensuremath{-}\ensuremath{\delta}}$ Films

Co-occurrence of Superparamagnetism and Anomalous Hall Effect in Highly Reduced Cobalt-Doped Rutile ${TiO}_{2 - δ}$ Films

S. R. Shinde, S. B. Ogale, J. S. Higgins, H. Zheng, A. J. Millis, V. N. Kulkarni, R. Ramesh, R. L. Greene, and T. Venkatesan

Phys. Rev. Lett. 92, 166601 – Published 23 April 2004

Abstract

We report a detailed magnetic and structural analysis of highly reduced Co doped rutile ${TiO}_{2 - δ}$ films displaying an anomalous Hall effect (AHE). The temperature and field dependence of magnetization, and transmission electron microscopy, clearly establish the presence of nanosized superparamagnetic cobalt clusters of $\sim 8 - 10 nm$ size in the films at the interface. The co-occurrence of superparamagnetism and AHE raises questions regarding the use of the AHE as a test of the intrinsic nature of ferromagnetism in diluted magnetic semiconductors.

Received 4 November 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.166601

Authors & Affiliations

S. R. Shinde^1,*, S. B. Ogale^1,2, J. S. Higgins¹, H. Zheng², A. J. Millis³, V. N. Kulkarni^1,†, R. Ramesh^1,2, R. L. Greene¹, and T. Venkatesan¹

¹Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
²Department of Materials Science, University of Maryland, College Park, Maryland 20742-42111, USA
³Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA

^*Electronic address: shinde@squid.umd.edu
^†On leave from Indian Institute of Technology, Kanpur, India.

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Vol. 92, Iss. 16 — 23 April 2004

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Physical Review Letters

Co-occurrence of Superparamagnetism and Anomalous Hall Effect in Highly Reduced Cobalt-Doped Rutile TiO2−δ Films

S. R. Shinde, S. B. Ogale, J. S. Higgins, H. Zheng, A. J. Millis, V. N. Kulkarni, R. Ramesh, R. L. Greene, and T. Venkatesan

Phys. Rev. Lett. 92, 166601 – Published 23 April 2004

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Co-occurrence of Superparamagnetism and Anomalous Hall Effect in Highly Reduced Cobalt-Doped Rutile ${TiO}_{2 - δ}$ Films