Nanocrystalline nickel-zinc ferrite prepared by the glass-ceramic route

Ni0.5Zn0.5Fe2O4 crystals having dimensions in the range 15-29 nm have been grown within berate glass by a two-stage heat treatment in the temperature range 873-953 K. Magnetic measurements have been carried out over the temperature range 20-300 K. The maximum coercive force corresponding to 0 K, (H-co) similar to 334 Oe, is obtained for a sample containing ferrite crystals of median diameter 15 nm. Field-cooled and zero-field-cooled magnetization data for different samples are consistent with the blocking temperatures extracted from the variation of coercive force as a function of temperature. The magnetocrystalline anisotropy constant for nanocrystalline nickel-zinc ferrite is found to be an order of magnitude higher than that for the bulk material