Magnetic Aftereffect and Magnetization Reversal of Sr-Ferrite Fine Particles

the magnetic aftereffect constant (Sv), the anisotropy field (HA) distribution and the rotational hysteresis integral (Rh) were measured for M-type hexagonal strontium ferrite (SrM) fine particles with various average particle diameters (D) and coercive forces (HcJ). The relations between Sv, the activation volume (v), HcJ, HA, and Rh were studied, as well as the effect of milling. Sv is constant and independent of the magnetic field. In Sv varies in proportion to In HcJ, and the relation HcJ¿v^¿2 was found to obtain in SrM particles not extensively subjected to milling. Sv increases and v decreases for SrM fine particles (D=0.3 ¿m) whose HA is widely distributed by milling, even though HcJ decreases markedly. Sv and v are related to the distribution of HA. As HcJ increases, Rh and v decrease, which indicates that the magnetization reversal mechanism of SrM fine particles approaches that of a coherent rotation mode.