Ferromagnetism in nanocrystalline epitaxial Co:TiO2 thin films.

Authors :: Pradhan, A. K.
Hunter, D.
Dadson, J. B.
Williams, T. M.
Zhang, Kai
Lord, K.
Lasley, B.
Rakhimov, R. R.
Zhang, Jun
Sellmyer, D. J.
Roy, U. N.
Cui, Y.
Burger, A.
Hopkins, C.
Pearson, N.
Wilkerson, A. L.
Source :: Applied Physics Letters; 5/30/2005, Vol. 86 Issue 22, p222503, 3p, 1 Diagram, 3 Graphs
Publication Year :: 2005
Abstract: We report on the observation of remarkable room-temperature ferromagnetism in nanocrystalline epitaxial Co:TiO<subscript>2</subscript> 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:TiO<subscript>2</subscript> films is controlled either by the interstitial Co<superscript>2+</superscript> 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 TiO<subscript>2</subscript>. [ABSTRACT FROM AUTHOR]