Magnetism and Charge Order in Nanocrystalline Orthorhombic SrFeO < inf > 3-δ < /inf >

Abstract

Orthorhombic SrFeO3-δ is synthesized through solid-state reaction in nanocrystalline form with controlled oxygen flow. Neutron diffraction measurement with Rietveld refinement and selected area electron diffraction (SAED) confirms the crystal structure. Magnetization against temperature shows that orthorhombic SrFeO3-δ is an antiferromagnet with Néel temperature (TN) of 230 K. Field-cooled hysteresis (M-H) measurements show exchange bias present in this system. It undergoes charge ordering near the Néel temperature and large change in resistivity around TN is found. Behavior of transport and magnetotransport properties are understood using the three-dimensional variable range hopping (3DVRH) mechanism and hysteresis is observed around TN in transport data. Ferromagnetic resonance (FMR) study shows that the linewidth is minimum around TN. Charge order and magnetic phase transition are coupled to each other around TN in the orthorhombic SrFeO3-δ system.