Segregation of Mn²⁺ dopants as interstitials in SrTiO<inf>3</inf> grain boundaries

Mn-doped SrTiO3 shows promising magnetic and electrical properties, but the doping mechanism remains unclear. In this research Mn4+ is found to substitute Ti in bulk SrTiO3, but Mn2+ segregates inside grain boundaries at both Sr and interstitial sites. Mn interstitial doping has never been reported, but is found possible with the formation of Sr vacancies. This finding is significantly different from the amphoteric doping of Mn2+ substituting Sr and Mn4+ substituting Ti sites, therefore leads to different understanding on the defect mediated electrical and magnetic properties of transition metal-doped perovskites.