Enhancement of initial permeability due to Mn substitution in polycrystalline Ni 0.50−xMn xZn 0.50Fe 2O 4

Abstract

The structural and magnetic properties of Mn substituted Ni 0.50− x Mn x Zn 0.50Fe 2O 4 (where x=0.00, 0.10 and 0.20) sintered at various temperatures have been investigated thoroughly. The lattice parameter, average grain size and initial permeability increase with Mn substitution. Both bulk density and initial permeability increase with increasing sintering temperature from 1250 to 1300 °C and above 1300 °C they decrease. The Ni 0.30Mn 0.20Zn 0.50Fe 2O 4 sintered at 1300 °C shows the highest relative quality factor and highest initial permeability among the studied samples. The initial permeability strongly depends on average grain size and intragranular porosity. From the magnetization as a function of applied magnetic field, M( H), it is clear that at room temperature all samples are in ferrimagnetic state. The number of Bohr magneton, n( μ B), and Neel temperature, T N, decrease with increasing Mn substitution. It is found that Mn substitution in Ni 0.50− x Mn x Zn 0.50Fe 2O 4 (where x=0.20) decreases the Neel temperature by 25% but increases the initial permeability by 76%. Possible explanation for the observed characteristics of microstructure, initial permeability, DC magnetization and Neel temperature of the studied samples are discussed.