Effect of Microwave Processing on Polycrystalline Hard Barium Hexaferrite

The present paper describes our results on the phase transformation (from crystalline to amorphous) of M-type hard barium hexaferrite, and consequently its conversion into soft ferrite by the application of magnetic energy at microwave frequency (2.45 GHz). The rapid volumetric heating of the conventionally prepared polycrystalline hexaferrite by microwave energy at a temperature of 950 °C in a short duration of only 5 min resulted in a decrystallized phase. The magnetic studies (M–H loops) of the resistively heated and MW processed samples have revealed a lowering in coercivity (from 188 to 2 mT) in the latter samples, thereby establishing the formation of soft ferrite. An attempt has also been made to understand the observed transformation from hard to soft ferrite.