Enhanced magnetism of perovskite oxides, Sr(Sn,Fe)O 3- δ , by substitution of nonmagnetic Ca and Ti ions

Magnetic properties of perovskite oxides, SrSn1-x Fe x O3-δ (x ≤ 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (Sr1-y Ca y )(Sn1-x Fe x )O3-δ and Sr(Sn1-x-y Fe x Ti y )O3-δ . The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O3-δ showed small saturation magnetizations as compared with non-Ti substituted one, the magnetization increased a little with Ti doping rates up to 15%. On the other hand, all Ca-substituted Sr(Sn, Fe)O3-δ showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe3+ and a doublet of Fe4+ were observed in Mossbauer spectra of Ca-substituted Sr(Sn, Fe)O3-δ with weak ferromagnetism, and two sextets of high spin Fe3+ were additionally observed in Mossbauer spectra of Ca-doped Sr(Sn, Fe)O3-δ with relatively strong ferromagnetism. When Sr(Sn, Fe)O3-δ were further codoped with Ca and Ti ions, they showed the stable and enhanced ferromagnetic properties. It is considered that magnetic polarons among high spin Fe3+ species are overlapped by shrinking or deforming the crystal structure of perovskite oxides. That is the magnetism induced by a chemical pressure of perovskite oxides.