Valence states and metamagnetic phase transition in partiallyB-site-disordered perovskiteEuMn0.5Co0.5O3

Abstract

The valence states of transition metals were studied by measuring the x-ray absorption spectra at both $\mathrm{Mn}\phantom{\rule{0.2em}{0ex}}{L}_{2,3}$ and $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}{L}_{2,3}$ edges of partially $B$-site-disordered perovskite $\mathrm{Eu}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$. By comparison with analogous spectra in various Co- and Mn-based compounds, the divalent state of the Co ions and the tetravalent state of the Mn ions were established analogous to ${\mathrm{Mn}}^{4+}∕{\mathrm{Co}}^{2+}$ charge ordering found by Dass and Goodenough [Phys. Rev. B 67, 014401 (2003)] in $\mathrm{La}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$. The specific heat and magnetic susceptibility data indicate the formation of the magnetically ordered state at ${T}_{C}\ensuremath{\sim}120\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The first-order metamagnetic transitions seen in $\mathrm{Eu}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$ at $T<{T}_{C}$ suggest the existence of antiferromagnetic and/or paramagnetic clusters embedded into the ferromagnetic matrix.