Synthesis and magnetic properties of Mg0.2Cr1.8−xFexO3 nanoparticles

We report the magnetic properties of Mg0.2Cr1.8−xFexO3 (for x=0.3, 0.5, 0.7, and 0.9) nanoparticle compounds. The oxides were produced by hydrothermal process and sintered at 600 °C for 12 h. The X-ray diffraction data indicate single phase corundum structure in all the samples. The Mössbauer spectra recorded at about 300 K show transition from paramagnetic to ordered magnetic spin state at x=0.5. The magnetization data reveal cluster-glass-like behavior of weakly ferromagnetic clusters in a dominant antiferromagnetic core. The shift in hysteresis loops observed along the magnetic field axis is associated with exchange bias effect. The exchange bias field measured at 10 K is also observed to correlate strongly with particle sizes. - Highlights: ► Prepared Mg0.2Cr1.8−xFe2O3 compounds by hydrothermal process. ► Anomalous variation of magnetization in low fields has been observed. ► The oxides exhibit exchange bias effects which appear to be sensitive to grain sizes. ► Samples with larger grains show more enhanced exchange bias effect. ► Results from 400 K to 10 K show evidence of strong antiferromagnetic interactions in the compounds.