FORMATION AND MICROWAVE-ABSORPTION OF BARIUM AND STRONTIUM FERRITE PREPARED BY SOL-GEL TECHNIQUE

Ba and Sr ferrites are prepared by sol-gel technique with different Fe /Ba(Sr) ratios in the starting materials. Magnetization, coercive, and anisotropy field strength are determined depending on the heat treatm ent of the gel and the iron/barium (strontium) ratio in the starting m aterial. A two-step heat treatment is used to prepare single-domain po wders with high magnetization. These powders prepared by sol-gel techn ique show single-domain behavior with specific magnetization sigma(S)= 649 A cm(2)/g and coercive field strength H-cM=402 kA/m in the case of Ba ferrite and sigma(S)=695 A cm(2)/g and H-cM=416 kA/m for Sr the fe rrite. Al-substituted ferrites with high anisotropy field strengths ar e prepared additionally. Ferromagnetic resonance absorption is used to determine the anisotropy field strength and to investigate the format ion process of the hexaferrite phase during the heat treatment. The be ginning of hexaferrite formation occurs at annealing temperatures belo w 700 degrees C.