Structural and magnetic phase transition observed in the YCrO3+γ compound

Abstract

We report on thermogravimetric, structural and magnetization measurements in the YCrO3+γ compound obtained by the co-precipitation method. The thermogravimentric analyses show that the weight losses which occur at three distinct steps are associated with water evaporation, formation of zircon-type YCrO4 compound and finally a phase transition from the tetragonal YCrO4 to the orthorhombic YCrO3. The X-ray diffraction measurements allied with the Rietveld refinement confirm such trend, that is, the observed X-ray patterns are consistent with a gradual growth of zircon-type YCrO4 with tetragonal structure and space group I41/amd for annealing temperatures up to 600 °C followed by the phase transition to the orthorhombic YCrO3 phase with space group Pbnm for annealing temperatures above 625 °C. The X-ray absorption near edge structure (XANES) spectra carried out in the Cr K-edge reveal that the oxidation states of Cr ions depend on the synthesis temperature. The T-dependencies of magnetic susceptibility point out a ferromagnetic-antiferromagnetic transition as function synthesis temperature. The Curie and Neel temperatures are in agreement with that reported in literature for the YCrO4 and YCrO3 compounds, respectively. Besides, the MvsH curves measured at 2 and 50 K are consistent with the observed magnetic states to each sample.