HOT-PRESSED MN-ZN-NI AND MN-ZN-CO FERRITES FOR MAGNETIC RECORDING-HEADS

Ni2+ and Co2+ substituted Mn-Zn ferrites have been developed as high-density magnetic recording materials by hot pressing using optimum sintering parameters. Ferrite series of the composition Mn0.6Zn0.4-xNi(x)Fe2O4 and Mn0.6Zn0.4-yCo(y)Fe2O4 were prepared by the hot-pressing technique wherein x and y varied from 0.0 to 0.4 in steps of 0.05. It yielded ferrites with improved magnetic properties having larger hardness (greater-than-or-equal-to 650 Vickers units), low porosity (< 0.1%), and small grain size (almost-equal-to 10-mu-m). The initial permeability increased, whereas the coercive field decreased for an Ni2+ concentration x or a Co2+ concentration y equal to 0.05. The maximum values of saturation magnetization equal to 4850 and 5250 G were obtained for x and y equal to 0.225 and 0.275, respectively. The Curie temperature increased appreciably, whereas the dc resistivity decreased for a larger substitution of Ni2+ and Co2+ ions. The observed variations have been qualitatively explained on the basis of relevant physical phenomena and existing models. The above properties render these ferrites suitable as core materials for magnetic recording devices.