Solvothermal synthesis of CoFe2O4 submicron compact spheres and tunable coercivity induced via low-temperature thermal treatment

Abstract

Compact CoFe2O4 submicron spheres were successfully prepared by a typical solvothermal synthesis method using potassium acetate as protective agent. The as-prepared spheres exhibited the onset of superparamagnetism. The saturation magnetization (Ms), remanent magnetization (Mr), coercivity (Hc) and remanence ratio R (Mr/Ms) were 46.79emu/g, 0.84emu/g, 18.4Oe and 0.018, respectively. Followed by thermal treatment at 250–600°C, the annealed spheres exhibited a sharp increment in coercivity without significant growth in crystal size. The coercivity of the sample annealed at 250°C was 597.5Oe and the sample annealed at 600°C was increased to 1371.7Oe. The probable mechanism of the increment in coercivity was suggested to be induced by the enhanced exchange interactions as the organics degraded in thermal treatment.