Effects of the Applied Magnetic Field for Measurements in the Law of Approach to Ferromagnetic Saturation (LAFS)

Abstract

Law of approach to ferromagnetic saturation (LAS) can be applied to isotropic magnet samples having either uniaxial anisotropy or cubic symmetry. Using the magnetization curves of samples, the relationships between polarization (J) and (1/H², H; applied field) or between susceptibility (dJ/dH) and (1/H³) are able to obtain. The magnetic anisotropy field (H_a) and saturation polarization (J_s) can be calculated using the slope and the intercept in the obtained relation lines. We found that the obtained J_s and H_a using above two relationships agree well when the applied field for magnetization measurements is sufficiently large that corresponds to the H_a of measured sample, >2.0 MA/m for Sr-ferrite. The above result was tried to apply to high anisotropy sample of newly developed (Nd_0.7Zr_0.3)(Fe_0.75Co_0.25)_11.5Ti_0.5N_1.3 having ThMn₁₂ structure, and it was confirmed that the applied field (H_appl) of more than about 6.7 MA/m gave the nearly same J_s and H_a of 1.67 T and 5.85 MA/m, respectively, using the above two relationships.