Intrinsic Ferromagnetism in the Diluted Magnetic Semiconductor   Co:TiO$_2$
  Here we present a study of magnetism in \CTO\ anatase films grown by pulsed laser deposition under a variety of oxygen partial pressures and deposition rates. Energy-dispersive spectrometry and transition electron microscopy analyses indicate that a high deposition rate leads to a homogeneous microstructure, while very low rate or postannealing results in cobalt clustering. Depth resolved low-energy muon spin rotation experiments show that films grown at a low oxygen partial pressure ($\approx 10^{-6}$ torr) with a uniform structure are fully magnetic, indicating intrinsic ferromagnetism. First principles calculations identify the beneficial role of low oxygen partial pressure in the realization of uniform carrier-mediated ferromagnetism. This work demonstrates that Co:TiO$_2$ is an intrinsic diluted magnetic semiconductor. 
H. Saadaoui, X. Luo, Z. Salman, X.Y. Cui, N.N. Bao, P. Bao, R.K.   Zheng, L. Tseng, Y.H. Du, T. Prokscha, A. Suter, T. Liu, ...
cond-mat.mtrl-sci