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artículo con referato
"Study of the relation between oxygen vacancies and ferromagnetism in Fe-doped TiO2 nano-powders"
Azucena M. Mudarra Navarro, Claudia E. Rodríguez Torres, Vitaliy Bilovol, A. Fabiana Cabrera, L.A. Errico and M. Weissmann
J. Appl. Phys. 115(22) (2014) 223908/1-8
In this work, we present an experimental and theoretical study of structural and magnetic properties of Fe doped rutile TiO2 nanopowders. We show that Fe-doping induces the formation of oxygen vacancies in the first-sphere coordination of iron ions, which are in +2 and +3 oxidation states. We found that Fe ions form dimers that share one oxygen vacancy in the case of Fe3+ and two oxygen vacancies in the case of Fe2+. The saturation magnetization is almost independent of iron concentration and slightly increases with the relative fraction of Fe2+. Ab initio calculations show that two Fe ions sharing an oxygen vacancy are coupled ferromagnetically, forming a bound magnetic polaron (BMP), but two neighbor BMPs are aligned antiparallel to each other. Extra electron doping plays a fundamental role mediating the magnetic coupling between the ferromagnetic entities: carriers, possibly concentrated at grain boundaries, mediate between the BMP to produce ferromagnetic alignment.
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