VISCOUS MAGNETIZATION OF CHROMIUM-DIOXIDE PARTICLES - EFFECT OF INCREASED MAGNETOCRYSTALLINE ANISOTROPY

Samples of chromium dioxide particles with a range of remanent coercivities H(r) but with identical particle size distributions have been prepared in order to study the effect of changes in the magnetocrystalline anisotropy on the time dependent magnetization. Comparison has been made with three cobalt modified gamma-Fe2O3 samples. The field dependend fluctuation field H(r), derived from measurements of magnetic viscosity as a function of applied field H, has been used to characterize the time dependent magnetic switching of the particles. Plots of H(f)/H(r) against H/H(r) are unaffected by anisotropy variations in either pigment type. The interpretation is that the details of the magnetics and the reversal mode are not primarily responsible for the more prounced time dependend magnetization effects observed in CrO2 and that the more likely explanation is the high state of magnetic excitation associated with the low Curie temperature.