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

Thermodynamic characteristics of the perovskite-like compound La2/3Ba1/3MnO3, exhibiting a structural phase transformation of the martensitic type with a characteristic temperature T-s approximate to 200 K, are studied in the temperature range 2-340 K. Step-like hysteretic temperature behavior of the effective heat capacity is revealed at 150-250 K 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 220 K and temperature hysteresis of the magnetic susceptibility clearly pronounced in the 40-100 K and 180-230 K regions. The Debye and Einstein temperatures, theta(D)=230 K and theta(E)=500 K, 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.