Magnetic properties of a new metal-ferrite composite

The magnetic properties of a new metal-ferrite composite, (Fe_0.2Co_0.8)_0.8[Fe_2.38Co_0.62O₄], are described. The metallic part is a cobalt-iron alloy Fe_0.2Co_0.8 of bcc and fcc structure and the spinel a cobalt-doped magnetite. This composite is made up of grains 0.1-0.5μm in size, and characterized by h_c=2300 Oe and σ_s=90 A m²/kg at room temperature, even after storage for one year in air. The saturation magnetization keeps a constant value up to 300°C, while the coercive field decreases at a rate of 0.35%/K between 20 and 200°C. However, a total reversibility of magnetic properties is observed between 20 and 100°C.