Process-optimization for preparing high coercivity modified magnetite particles

The dependence of magnetic properties on composition and processing of nonacicular, Co, Mn and Zn modified magnetite particles obtained by coprecipitating from aqueous solutions and heat treatment was explored. It was found that a coercivity of 700 to 1700 Oe, a saturation (at 20 kOe) and residual magnetization of 79 to 87 cmu/g and 40 to 52 cmu/g, respectively; a squareness ratio of 0.48 to 0.63 can be adjustable by doping amount and heat treatment. Zn was found to raise the saturation magnetization and lower the temperature coefficient of coercivity (TCC). The heat treatment at its precursor magnetic phase state before final reduction significantly enhances the coercivity of the final magnetic phase after reduction. Due to the large coercivity, high magnetization, and low TCC value, these particles may find applications in high density recording.<
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