Magnetization Process of Magnetic Fluid

The magnetization curves of magnetic fluids in liquid and frozen states, together with magnetic field cooling effects and particle concentration dependences, are reported. Fluids were frozen in liquid nitrogen under a 3.6 kOe field, and magnetization curves measured as a function of the angle Q (= 0, 45, 90°) between the field during freezing and the measuring field. When diluted in the liquid state, the magnetization decreased linearly with decreased ferromagnetic particle concentration, but the field dependence of the magnetization was qualitatively the same. Asimow´s expression for the magnetization curve of non-interacting randomly oriented particles is fitted to the experimental results; from this, the field-induced uniaxial anisotropy energy was estimated at about 8 × 10³ erg/cc.