Using complementary experiments we show that the room temperature ferromagnetism observed in anatase Co:TiO2 films is not carrier mediated, but coexists with the dielectric state. TEM and x-ray absorption spectroscopy reveal a solid solution of Co in anatase, where Co is not metallic but in the +2 state substituting for Ti. Measurements at 300 K yield a Ms of 1.1 µB/Co atom, while all films are highly insulating. The evidence of intrinsic ferromagnetism in the dielectric ground state of Co:TiO2 leads to new considerations for the origin of ferromagnetism in transition metal doped oxides.
Revised: April 7, 2011 |
Published: April 22, 2005
Citation
Griffin K.A., A. Pakhomov, C.M. Wang, S.M. Heald, and K.M. Krishnan. 2005.Intrinsic Ferromagnetism in Insulating Cobalt Doped Anatase TiO2.Physical Review Letters 94, no. 15:Art. No. 157204.PNNL-SA-43211.