Positive exchange bias effect in LaCr0.5Fe0.5O3 perovskite

Abstract

This work reports the synthesis and characterization of perovskites with LaCr0.5Fe0.5O3 stoichiometry. The perovskite was synthesized by an alternative route to traditional sol-gel method, the precursor was prepared using gelatin as a chelating agent and further calcined 2 h at 1200 °C. The sample is investigated by combining X-ray diffraction, Mössbauer spectroscopy and scanning electron microscopy with chemical microanalysis. The Rietveld refinement showed the formation of the La(OH)3 secondary phase in addition to the main perovskite phase. The M-T measurements showed a negative field cooling magnetization with a compensation temperature depending on the cooling field. The findings in the M-T measurements are discussed in terms of competition between the single ion magnetic anisotropy and the antisymmetric Dzyaloshinsky-Moriya interactions. The M-H measurement at 300 K revealed a hysteretic behavior ascribed to ferromagnetic clusters. At low temperature the field cooling M-H curves showed a positive exchange bias field and a downward shift of the hysteresis. The shifting of the hysteresis and the exchange bias field began at 250 K, a bit below the Néel transition. The hysteresis shift is ascribed to an antiferromagnetic coupling between the ferromagnetic clusters and the antiferromagnetic LaCr0.5Fe0.5O3 phase.