Hyperfine Fields and Particle Size Distribution in Small Particle MnZn Ferrites

Ultrafine and nearly spherical MnZn ferrite particles are prepared under mild hydrothermal conditions. Magnetic hyperfine field distributions in these microcrystallites are investigated in relation to tiieir particle size distributions. The hydrothermal ferrite powders are found to be superparamagnetic, with a narrow particle size distribution peaking at 11.5 nm. High densities (>99.7% of theoretical) are obtained upon sintering the green ferrites at relatively low temperatures (1000 °C), without the use of any sintering aids.