Electronic states of charge-orderingNd0.5Sr0.5MnO3probed by photoemission

Abstract

Electronic structures of the charge-ordering manganite ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}(x\ensuremath{\sim}0.5)$ have been studied by resonant and high-resolution photoemission. The Mn $2p$ (Nd $3d)$ resonant photoemission confirmed the Mn $3d$ (Nd $4f)$ states hybridized with the O $2p$ states. The high-resolution Mn $3p$ resonance spectra show a clear transition from the metal to the charge-ordered insulator for $x=0.5$ upon cooling while a Fermi cutoff is seen for $x=0.47$ at all temperatures, suggesting that the transition is induced by a subtle competition between the charge-ordering instability and the double-exchange interaction. Temperature and filling dependence of the spectra implies that the electronic states change not gradually but suddenly at the phase boundary.