Magnetic and structural properties of [Co.sub.0.8][Mn.sub.x][Fe.sub.2.2-x][O.sub.4] (x=0.2, 0.4, 0.6, 0.8) polycrystalline powders synthesized by sol-gel process

[Co.sub.0.8][Mn.sub.x][Fe.sub.2.2-x][O.sub.4] (x = 0.2, 0.4, 0.6, and 0.8) powders are prepared by a sol-gel process and annealed at different temperatures and magnetic and structural properties are measured. The decrease in coercivity ([H.sub.c]) is attributed to the content decrease in [Co.sup.2+] on B sites and increasing grain sizes at higher annealing temperature have an intensive influence on [H.sub.c].