Ferromagnetism in nanocrystalline epitaxial Co:TiO₂ thin films

Authors

• Aswini K. Pradhan, Center for Materials Research, Norfolk State UniversityFollow
• D. Hunter, Center for Materials Research, Norfolk State University, Norfolk, Virginia
• J.B. Dadson, Center for Materials Research, Norfolk State University, Norfolk, Virginia
• T.M. Williams, Center for Materials Research, Norfolk State University, Norfolk, Virginia
• Kai Zhang, Center for Materials Research, Norfolk State University, Norfolk, Virginia
• K. Lord, Center for Materials Research, Norfolk State University, Norfolk, Virginia
• B. Lasley, Center for Materials Research, Norfolk State University, Norfolk, Virginia
• Rakhim R. Rakhimov, Center for Materials Research, Norfolk State UniversityFollow
• Jun Zhang, University of Nebraska - LincolnFollow
• David J. Sellmyer, University of Nebraska-LincolnFollow
• U.N. Roy, Department of Physics, Fisk University, Nashville, Tennessee
• Y. Cui, Department of Physics, Fisk University, Nashville, Tennessee
• A. Burger, Department of Physics, Fisk University, Nashville, Tennessee
• C. Hopkins, College of William and Mary, Applied Research Center, Newport News, Virgina
• N. Pearson, College of William and Mary, Applied Research Center, Newport News, Virgina
• A.L. Wilkerson, College of William and Mary, Applied Research Center, Newport News, Virgina

Document Type

Article

Date of this Version

5-30-2005

Comments

Published by American Institute of Physics. Appl. Phys. Lett. 86, 222503 (2005). ©2005 American Institute of Physics. Permission to use. http://apl.aip.org/jap/.

Abstract

We report on the observation of remarkable room-temperature ferromagnetism in nanocrystalline epitaxial Co:TiO₂ films grown on sapphire (0001) substrates by a pulsed-laser deposition technique using high-density targets. The films were characterized by x-ray measurements, atomic force microscopy, micro-Raman, electron-paramagnetic resonance, and magnetization studies. The films exhibit three-dimensional islandlike growth that contains nanocrystalline particles. Our experimental results suggest that the remarkable ferromagnetism in Co:TiO₂ films is controlled either by the interstitial Co²⁺ ions or small clusters, which are mainly present at the interface and on the surface of the films. Our work clearly indicates that Co interstitials and nanoclusters cause room-temperature ferromagnetism in Co-doped TiO₂.