Spin-reorientation transition in SrNdFeO₄

The spin-reorientation transition of layered perovskite oxide SrNdFeO₄ has been investigated through powder x-ray and neutron diffraction, magnetic susceptibility, specific heat and ⁵⁷Fe Mössbauer spectrum measurements. This oxide presents tetragonal symmetry (space group: I4/mmm) and the FeO₆ octahedron is axially distorted. Through its magnetic susceptibility and specific heat measurements, two magnetic anomalies were found at around 15 and 36 K. From ⁵⁷Fe Mössbauer spectra and neutron diffraction profiles of SrNdFeO₄, it has been elucidated that the anomalies observed at 15 and 36 K correspond to the antiferromagnetic ordering of the Nd³⁺ ion and a change in the direction of magnetic moment of the Fe³⁺ ion, respectively. The magnetic structures above and below the spin-reorientation transition temperature were determined. The spin-reorientation transition observed in SrNdFeO₄ has been induced by the onset of local magnetic interactions between the neodymium and iron sublattices.