Crossover from charge-localized state to charge-ordered state in Pr2/3Ca1/3MnO3.

Abstract

In ${\mathrm{Pr}}_{\frac{2}{3}}{\mathrm{Ca}}_{\frac{1}{3}}\mathrm{Mn}{\mathrm{O}}_{3}$, we have found a crossover from a charge-localized state to a charge-ordered (CO) state. Linear-thermal-expansion and magnetostriction measurements up to 14 T show that for temperatures below ${T}_{p}\ensuremath{\sim}400$ K a charge localization is present as in the case of ${\mathrm{La}}_{\frac{2}{3}}{\mathrm{Ca}}_{\frac{1}{3}}\mathrm{Mn}{\mathrm{O}}_{3}$. Below ${T}_{\mathrm{CO}}\ensuremath{\approx}210$ K, a charge ordering, as found in some ${R}_{0.5}{A}_{0.5}\mathrm{Mn}{\mathrm{O}}_{3}$ ($R\ensuremath{-}A=\mathrm{L}\mathrm{a}\ensuremath{-}\mathrm{C}\mathrm{A},\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{r}\ensuremath{-}\mathrm{C}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{r}\ensuremath{-}\mathrm{S}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{N}\mathrm{d}\ensuremath{-}\mathrm{S}\mathrm{r}$) compounds, is observed. A magnetic field suppresses the CO state below ${T}_{\mathrm{CO}}$ giving rise to a first-order structural transition. A continuous change in volume is measured between ${T}_{\mathrm{CO}}<T<{T}_{p}$. The electrical behavior is similar to the structural behavior, and is the result of the strong spin-charge-lattice coupling present in the colossal-magnetoresistance perovskites.