“Influence of the thermal treatment in the phase formation and magnetic behaviour in metal transition doped TiO2”

A. F. CABRERA; C.E. RODRÍGUEZ TORRES; L. ERRICO; F.H. SÁNCHEZ

La Plata, Argentina

Workshop; Hyperfine Interactions at La Plata-International Workshop; 2005

There has been much attention paid to diluted magnetic semiconductors (DMS) in the last decade, but the origin of the ferromagnetism in doped semiconductors remains as an issue of discussion. Some authors claim that the ferromagnetism depends on the oxygen deficiency while others do not exclude the possibility of magnetic atom segregation, essentially in thin- film systems. For these reasons, it is important to clarify the origin of magnetism in DMS. In this work other possible route of DMS preparation is explored as well as the possibility to obtain new materials with high Curie temperature. Based on recent theoretical results that predict magnetism in transition metal doped rutile TiO2, mixtures of 5 % Fe, Ni, Co or Mn and TiO2 were prepared,  which were thermally treated at 673, 773K and 973K for 12 h in air. Samples were characterized by Mössbauer Effect spectroscopy (Fe doped TiO 2), X-ray diffraction (XRD), AC- susceptibility and vibrating sample magnetometry (VSM). XRD patterns show diffraction lines belonging to rutile, anatase and the transition metals employed as dopants. After a thermal treatment at 973K, ilmenite (MTiO 3) was detected in Ni, Mn and Co doped samples, while hematite and rutile were observed in the Fe one. The ACsusceptibility measurements display a behaviour corresponding to mixtures of two phases one paramagnetic and one antiferromagne tic (MTiO3). An hysteretic behaviour  was observed in all samples.