Possible Existence of Two Charge-Ordered Phases in Pr1−xCaxMnO3 for 0.40 ≤ x ≤ 0.50

Abstract

We report the Ca-concentration dependence of crystal structure, electrical transport and magnetic properties in the charge-ordered manganite Pr1−xCaxMnO3 for 0.40 ≤ x ≤ 0.50. We have observed an abrupt change in the thermoelectric power at x ∼ 0.425, which implies that the charge-ordered phase discontinuously changes at this composition. We further find that the lattice distortion and ferromagnetic volume fraction also change at that particular concentration. These results indicate that the checker-board-type charge order near x = 0.50 is unstable below x = 0.425. A possible origin for this phenomenon is discussed.