Metal-semiconductor transition and ferroelectricity in charge ordered La0.5Ba0.5FeO3 perovskite

The charge disproportionate correlated electronic system La_0.5Ba_0.5FeO₃; synthesized by conventional solid state reaction route, exhibits novel properties. The sample undergoes semiconductor-metal type transition at T_SM=102K. A crossover of electrical conduction mechanism from variable range hopping to small polaron hopping occurs around 210K, well above T_SM. Analysis of the transport, magnetic susceptibility and magnetization data in the light of De Gennes proposal indicates the formation of canted antiferromagnetic spin order preceded by charge ordering in La_0.5Ba_0.5FeO₃ perovskite. The observed resistive transition is considered to be associated with the onset of weak ferromagnetic ordering in the canted antiferromagnetic spin state. Another noteworthy feature is the observation of Polarization-Electric field (P-E) hysteresis loop signifying the appearance of ferroelectricity in the charge ordered state.