Cation redistribution

Cation redistribution causes a short range ferrimagnetic ordering in dry milled and wet milled zinc ferrites that forms magnetic clusters which contribute to saturation magnetisation. Superparamagnetic clusters are also coupled with the ferrimagnetic clusters resulting in the nonsaturation of hysteresis curves even after applying 10 KOe field. The a-Fe2O3 may be acting as a facilitator to redistribute the cations. The oxygen deficiency produced by the high energy ball milling causes the superexchange bonds to break, which results in spin disorder especially in surface. This surface spin disorder also contributes to magnetisation. Thermomagnetisation studies on dry milled zinc ferrites establish partial cation redistribution and spin glass like surface layer. A-A and B-B do plays a role at lower temperatures. A-A and B-B interactions reduce the magnetisation below the transition temperature in zero field cooled condition. In field cooled conditions, the antiferromagnetic ordering is suppressed by the field applied which orients the clusters in the field direction. Ac magnetic susceptibility results are also in tune with VSM results. Lack of spin glass like properties and less enhancement of saturation magnetisation in wet milled zinc ferrite is due to the resistance offered by the milling medium (toluene) to the direct kinetic energy transfer from balls to powder.