Magnetic Coercivity of Cobalt Fine Particles in 2% Co-Cu Alloy

Magnetic coercivity, its temperature dependence and saturation remanence (remanent magnetization remaining after the application of a field of 17 kOe) of cobalt precipitated particles in copper-cobalt alloy containing ca. 2 wt % cobalt were measured as a function of aging time. A coercive force and a remanence field (required to reduce a magnetic remanence to zero) are interpreted in terms of magnetocrystalline and shape anisotropies, and particle-size dependence of the coercive force is discussed in terms of thermal fluctuation of magnetic moment of cobalt single domain particles. Distributions of shape and size of magnetic particles were determined by magnetic analysis. It was found that the axial ratio of the particles increases with aging time.