Volume 516, Issue 1-2 pp. 70-71
Original Paper

Superparamagnetism in Co ion-implanted epitaxial anatase TiO2 thin films

D.H. Kim

D.H. Kim

School of Physics and ReCOE, Seoul National University, Seoul 151-747, Korea

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J.S. Yang

J.S. Yang

School of Physics and ReCOE, Seoul National University, Seoul 151-747, Korea

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Y.S. Kim

Y.S. Kim

School of Physics and ReCOE, Seoul National University, Seoul 151-747, Korea

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Y.J. Chang

Y.J. Chang

School of Physics and ReCOE, Seoul National University, Seoul 151-747, Korea

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T.W. Noh

Corresponding Author

T.W. Noh

School of Physics and ReCOE, Seoul National University, Seoul 151-747, Korea

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S.D. Bu

S.D. Bu

Department of Physics, Chonbuk National University, Chonju 561-756, Korea

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Y.-W. Kim

Y.-W. Kim

School of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea

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Y.D. Park

Y.D. Park

School of Physics and CSCMR, Seoul National University, Seoul 151-747, Korea

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S.J. Pearton

S.J. Pearton

Department of Materials Science and Engineering, University of Florida, Gainsvill, FL 32611, USA

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J.-H. Park

J.-H. Park

Department of Physics and ESSC, Pohang University of Science and Technology, Pohang 790-784, Korea

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First published: 10 February 2004

Abstract

We investigated the magnetic properties of Co doped anatase TiO2 thin films. To incorporate Co into epitaxial anatase TiO2 thin films, we implanted them with Co+ ions. The temperature dependence of the magnetization of the implanted films, taken in zero-field-cooling (ZFC) and field-cooling conditions, exhibits the main features of superparamagnetic system: the ZFC curves are rounded at the blocking temperature (TB) and a paramagnetic-like behavior above TB. After annealing the films, TB increased with increasing annealing temperature. These phenomena can be explained by the formation of Co (or ferromagnetic Co compound) particles and their growth during annealing, as directly observed with transmission electron microscopy.

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