Enhancement of Néel temperature and electrical resistivity of Mn–Ni–Zn ferrites by Gd3+ substitution

Structural, magnetic, and dielectric properties of various Mn0.5Ni0.1Zn0.4Fe2−xGdxO4 sintered at 1200 °C were investigated thoroughly. The samples were synthesized by standard solid state reaction technique. The crystal structure was characterized by X-ray diffraction (XRD), which has confirmed the formation of single phase spinel structure. Bulk density, average grain size and initial permeability are found to decrease with increasing Gd content. For Gd substituted compositions, the value of Néel temperature is found to increase considerably, about 200 °C higher than that of the parent composition. The value of magnetic loss and dielectric loss are observed to decrease with the substitution of Gd3+ for the frequencies greater than 0.54 MHz and 10 kHz respectively. It is found that the AC resistivity (ρac) increases with the substitution of Gd3+ and the highest value of ρac is observed for the composition with x = 0.03, about 600 times greater than that of parent composition. Keywords: Average grain size, FESEM, Néel temperature, Resistivity, RQF, Spinel ferrite