Evidence of oxygen-vacancy-induced ferromagnetic order in single crystal Mn-doped SrTiO3

The appearance of ferromagnetic order in the presence of oxygen vacancies has been investigated in dilute Mn-doped SrTiO3 single crystals. The sample without vacancy is paraelectric and paramagnetic down to low temperature. However, incorporation of vacancy makes the system metallic and clear ferromagnetic hysteresis loop is observed at low temperature. X-ray diffraction, x-ray absorption near edge spectroscopy measurement do not reveal any signature of secondary magnetic phase. Diffuse reflectivity measurement negates the bound magnetic polaron model for ferromagnetism in the reduced system and thus spontaneous magnetism suggests the possibility of a carrier-mediated Ruderman-Kittel-Kasuya-Yosida mechanism. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4738785]