Enhanced magnetism of perovskite oxides, Sr(Sn,Fe)O_3-δ, by substitution of nonmagnetic Ca and Ti ions

Magnetic properties of perovskite oxides, SrSn_1-xFe_xO_3-δ (x ≤ 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (Sr_1-yCa_y)(Sn_1-xFe_x)O_3-δ and Sr(Sn_1-x-yFe_xTi_y)O_3-δ. The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O_3-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)O_3-δ showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe³⁺ and a doublet of Fe⁴⁺ were observed in Mössbauer spectra of Ca-substituted Sr(Sn, Fe)O_3-δ with weak ferromagnetism, and two sextets of high spin Fe³⁺ were additionally observed in Mössbauer spectra of Ca-doped Sr(Sn, Fe)O_3-δ with relatively strong ferromagnetism. When Sr(Sn, Fe)O_3-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.