Magnetic properties of MnZn ferrites prepared by soft chemical routes

MnZn ferrites with different composition have been synthesized by soft chem istry routes using oxalate precursors with the partial replacement of water by acetone as the solvent. Toroids were sintered at 1250 degrees C for 3 h in O-2/N-2 atmosphere. Sintering conditions significantly changed macrosco pic characteristics as density and initial permeability for different compo sition. Variation of the complex permeability with frequency have been meas ured over a wide range of frequency, up to 1.8 GHz where dispersion is attr ibuted to spin resonance. No additives for increasing densification were em ployed. Samples exhibit the highest permeability values for Mn0.8Zn0.2Fe2O4 . An anomalous effect is observed when copper is added to MnZn ferrites. Th e initial permeability (mu(i)) values do not exhibit much variation with te mperature, except near T-c where it falls sharply. Curie point and magnetic losses are related with composition. (C) 2000 American Institute of Physic s. [S0021-8979(00)23308-2].