THERMALLY ACTIVATED RELAXATION-TIME OF A SINGLE-DOMAIN FERROMAGNETIC PARTICLE SUBJECTED TO A UNIFORM-FIELD AT AN OBLIQUE ANGLE TO THE EASY-AXIS - COMPARISON WITH EXPERIMENTAL-OBSERVATIONS

New asymptotes of the relaxation time of the magnetic moment of a sing le domain particle with a uniform magnetic field applied at an oblique angle to the easy axis (in excellent agreement with exact numerical r esults from the Fokker-Planck equation for the Neel-Brown model) are u sed to model the experimental angular variation of the switching field for individual Co and BaFeCoTiO particles. Good agreement is obtained , justifying the Neel-Brown (in effect, the Kramers) conception of the superparamagnetic relaxation process and allowing one to deduce the v alue of the damping constant (itherto almost unknown).