Oxygen Vacancy and Dilute Magnetism of SnO2 doped with Fe and Metal ions

K. NOMURA; M . MUDARRA; C. RODRÍGUEZ TORRES; L. ERRICO; F. CABRERA; M. WEISSMANN

Conferencia; Mediterranean conference on the Applications of the Mössbauer Effect; 2015

1．To develop room temperature ferromagnetic semiconductors, we have studied on magnetic ions doped oxide semiconductorswith large bandgap. The interested phenomena have been reported until now1).2．The ferromagnetism was sometimes observed by doping dilute Fe ions intoSnO2although only paramagnetic doublets was observed in57Fe Mossbauer spectra2).The magnetization decreased after annealing for long hours.Dopping Sb into Fe doped SnO2 induced in ferromagnetism2). The broading peaks of SnO2were observed by 119Sn Mosbauer spectrometry under magnetic field3). These magnetic behaviers may be due to the lattice deformation and the oxygen vacancy induced by doping Fe ions. The isomershift () and quarupole splitting (Q) obtained by the experiments are shown in Fig. 1. The experimental results are grouped into four: I1, I2 and I3 due to Fe3+ and I4 due to Fe2+. The groups I1 and I2 are observed with high and low peak intensity, respectively. The groups I3 and I4 are additionally observed in samples prepared by ion implatntation and ball milling, respectively. 3．Substituting Sn4+by Fe3+ induces the oxygen vacancy. The following modelsare calculated by ab initio 4) : Sn15FeO31 with nearest oxygen vacancy (Fe-VO1), with second nearest oxygen vacancies (Fe-VO2) and with third nearest oxygen vacancy (Fe-VO3), and the different configurations of two substituted Fe and one oxygen vacancy (Fe-VO-Fe) and two substituted Fe ions and two oxygen vacancies(Fe-2VO-Fe).The calculated IS values are shifted by about -0.1 mm/s in order to compare with experimental values at room temperature as shown Fig.1.4．Bound magnetic polarons (BMP) are formed by two Fe ions linked with an oxygen vacancy, and two BMP become anti-ferromagnetic behavior becausethe formation energy, Eanti-Eferro=ΔE=-0.05 eV. When doping electrons with Sb5+, ΔE=+0.3eV, that is ferromagnetic coupling between two BMP. The oxygen vacancy and eleectron doping play an important role of magnetism for Fe doped SnO2.References1) K. Nomura, RADIOISOTOPES 62 (2013)857.2)K. Nomura, et. al.,Phys. Rev.B75 (2007) 184411,3)K. Nomura, et. al., Hyperfine Interact. 184 (2008)57,4)A. M. N. Mudarra, et. al. J. Phys. Chem.C119 (2015)5596.