MAGNETIC AND ELECTRICAL-PROPERTIES OF HOT-PRESSED NI-ZN-LI FERRITES

The magnetic properties of Ni-Zn ferrites have been upgraded by preparing hot-pressed Ni0.4Zn0.6-2xLixFe2+xO4 ferrites wherein 2xZn2+ ions have been substituted by xLi1+ and xFe3+ ions. This results in an increase of saturation magnetization, Curie temperature and dielectric constant, whereas resistivity and initial permeability are reduced. The values of saturation magnetization, Curie temperature and dielectric constant are improved due to hot pressing in which grain growth and densification are controlled simultaneously. The variations of saturation magnetization and Curie temperature can be explained by the preferential site occupancy of Li1+ and Ni2+ ions at the tetrahedral site, sublattice magnetization with canted spin structure, and magnetic exchange interactions. The inferences drawn from the bulk magnetic properties of these ferrites conform with the conclusions drawn from variations of internal magnetic field, obtained from Mossbauer studies of these samples. The decrease in d.c. resistivity due to substitution of Li1+ ions is attributed to increased hopping due to formation of Fe2+ and Ni3+ ions.