Structural, electric and magnetic properties of CoFe1.8RE0.2O4 (RE=Dy, Gd, La) bulk materials

We investigated the influence of rare earth (RE) additions on the structural, dielectric, magnetic and magnetostrictive properties of cobalt ferrite bulk materials. Three lanthanide ions with different ionic radii and magnetic properties were used as dopants: Dy, Gd, La. The structural properties of the sintered samples were investigated using X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The room temperature hysteresis loops were obtained using a vibrating sample magnetometer. The frequency dependence of dielectric permittivity and tangent loss was investigated in the 20 Hz–20 kHz range. The variation of the magnetoelectric response with applied dc magnetic field was analyzed. The insertion of rare earth elements influenced the structural characteristics of the samples (density, cell edge, porosity) and the magnetic and electric properties. An increase in coercive field and a decrease in saturation magnetization and magnetostriction coefficient were observed. These results can be partially explained by the weaker nature of the RE3+–Fe3+ interaction compared to Fe3+–Fe3+ interaction and to the antiferromagnetic alignment of the REFeO3 second phase observed in the diffraction patterns after sintering process.

► CoFe1.8RE0.2O4 bulk materials sintered at 1250 °C for 5 h were investigated.
► XRD diffractograms revealed the presence of a second phase of REFeO3.
► RE substitutions increased the coercive field and decreased the saturation magnetization.
► Small amounts of RE ions decreased the maximum magnetostriction coefficient.