Correlation between Mn and Ru valence states and magnetic phases inSrMn1−xRuxO3

Abstract

The electronic structures of ${\mathrm{SrMn}}_{1\ensuremath{-}x}{\mathrm{Ru}}_{x}{\mathrm{O}}_{3}$ $(0\ensuremath{\le}x\ensuremath{\le}1)$ have been investigated by employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). Both Mn and Ru ions are nearly tetravalent $({\mathrm{Mn}}^{4+},\phantom{\rule{0.28em}{0ex}}{\mathrm{Ru}}^{4+})$ for the end members of $x=0$ $({\mathrm{SrMnO}}_{3})$ and $x=1$ $({\mathrm{SrRuO}}_{3})$. In the Ru-dilute concentration $(x\ensuremath{\le}\ensuremath{\sim}0.2)$, Ru ions are pentavalent $({\mathrm{Ru}}^{5+})$, which transform neighboring Mn ions into the trivalent ${\mathrm{Mn}}^{3+}$ states via electron charge transfer. In the intermediate substitution regime, Mn and Ru ions are in the inhomogeneously mixed-valent states $({\mathrm{Mn}}^{3}\ensuremath{-}{\mathrm{Mn}}^{4+}$ and ${\mathrm{Ru}}^{4}\ensuremath{-}{\mathrm{Ru}}^{5+})$. Finite Mn $2p$ XMCD signals are observed for $x>0$, in agreement with the ferromagnetic, spin-glass, cluster-glass ground states depending on $x$. The unoccupied Mn $3d$ and Ru $4d$ states, determined from the measured O $1s$ XAS spectra and the calculated density of states, support these findings.