Structure and magnetic properties of the perovskite YCo_0.5Fe_0.5O₃

YCo_0.5Fe_0.5O₃, in a structure of perovskite, has been successfully prepared with citrate precursors at 950-1100°C in air by the sol-gel method. The X-ray diffraction patterns show that the samples are orthorhombic within the space group Pnma, where the Co and Fe ions are disordered at the 4b crystallographic sites. The crystal structure refinement undertaken by the Rietveld method has shown that the distortion of Co(Fe)O₆ octahedra are large, where the ratio of Co/Fe-O bonding length along a axis to that in the bc plane is about 1.07. Such a large crystal lattice distortion implies a strong lattice-magnetism coupling, which may be utilized in the magnetoelectric devices. Magnetic measurement indicates that the YCo_0.5Fe_0.5O₃ is antiferromagnetic but showing weak ferromagnetism. We find that Fe³⁺ ions are in high-spin states, while Co³⁺ ions are in low-spin states which do not contribute to the magnetism. Both Fe³⁺ and Co³⁺ ions are not Jahn-Teller activated although the lattice distortion is large.