Study of the relation between oxygen vacancies and ferromagnetism in Fe-doped TiO2 nano-powders

A. MUDARRA NAVARO; C. RODRIGUEZ TORRES; V. BILOVOL; F. CABRERA; L. A. ERRICO; M. WEISSMANN

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2014 vol. 115 p. 223908 - 223908

0021-8979

Pagina inicial: 223908-1 Pagina final: 223908-8 8 paginas. 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 þ2 and þ3 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 Fe2þ. 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.