Electronic structure and magnetism of SrTi1-xMnxO3 ceramics

Abstract

Having reviewed the previous studies on Mn-doped SrTiO3 materials, we found that Mn2+ and/or Mn4+ ions are usually present in the SrTiO3 host lattice and lead to paramagnetic, spin-glass, or ferromagnetic (FM) behavior. Mn2+ can occupy at both octahedral (Ti) and dodecahedral (Sr) sites, while Mn4+ only occupies the Ti site. To get more insight into this material system, we have prepared polycrystalline SrTi1-xMnxO3 (x = 0–0.10) samples by solid-state reactions. The results obtained from analyzing the powder X-ray diffraction patterns, and Raman scattering, X-ray absorption, and electron-spin-resonance spectra indicate an incorporation of Mn2+ and Mn3+ ions into the SrTiO3 host lattice. Isolated Mn2+ ions are dominant in the samples with x ≤ 0.02 and can occupy both Ti and Sr sites, leading to two sets of the hyperfine sextet lines. An increase in the Mn content with x > 0.02 enhances the Mn3+ concentration and stimulates the formation of a minor tetragonal phase besides the main cubic phase of SrTiO3. This enhances the Lorentzian-shaped broad background line of dipolar and magnetic interactions between Mn ions. Besides the resonant signals of isolated Mn2+ ions and dipolar/magnetic interactions between Mn ions, there is also the resonant signal associated with intrinsic defects. We believe that intrinsic defects together with the Mn doping at suitable concentrations (x > 0.02) are an important pivot for tailoring room-temperature FM order in SrTi1-xMnxO3 ceramics.