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

In Pr2/3Ca1/3MnO3, 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 similar to 400 K a charge localization is present as in the case of La2/3Ca1/3MnO3. Below T(CO)approximate to 210 K, a charge ordering, as found in some R(0.5)A(0.5)MnO(3) (R-A=La-Ca, Pr-Ca, Pr-Sr, Nd-Sr) compounds, is observed. A magnetic field suppresses the CO state below T-CO giving rise to a first-order structural transition. A continuous change in volume is measured between T-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.