Observation of the charge order in perovskite manganite Pr _0.5Ca _0.5MnO ₃ by Mössbauer quadrupole effect

The charge order in a perovskite manganite Pr _0.5Ca _0.5MnO ₃ was investigated by Mössbauer spectroscopy. The quadrupole splitting and the absorption line width jump to an increase when lowering the temperature below 230 K (T _co), which is indicative of a phase transition to a monoclinic structure due to the charge ordering, or due to a local Jahn-Teller effect due to the presence of Mn ³⁺ ions. The intensity ratio of the doublet lines also changes at T _co. Local and dynamical Jahn-Teller effect (polarons) with a relaxation time of 10 ^-8 s is present even in the metallic state.