Low-temperature phase segregation in La2∕3Ba1∕3MnO3: Manifestation of nonequilibrium thermodynamics

Abstract

Thermodynamic characteristics of the perovskite-like compound La2∕3Ba1∕3MnO3, exhibiting a structural phase transformation of the martensitic type with a characteristic temperature Ts≈200K, are studied in the temperature range 2–340K. Step-like hysteretic temperature behavior of the effective heat capacity is revealed at 150–250K and attributed to the discrete kinetics and a latent heat of the martensitic transformation. The magnetic subsystem is found to exhibit a magnetic glass state below 220K and temperature hysteresis of the magnetic susceptibility clearly pronounced in the 40–100K and 180–230K regions. The Debye and Einstein temperatures, θD=230K and θE=500K, respectively, derived from the experimental Debye–Waller factors for the La∕Ba, Mn, and O sublattices, are used to refine contributions from the structural and magnetic transformations to the heat capacity and to reveal thermodynamically nonequilibrium states.