REVERSIBLE TRANSVERSE SUSCEPTIBILITY OF PARTICULATE RECORDING MEDIA

The response of a system to an infinitesimal perturbation becomes sing ular if the system changes its degree of metastability, i.e., if it ha s an inflection point. This theory is used to calculate the reversible transverse susceptibility chi(t) of a single domain particle executin g a major hysteresis loop under the influence of a field H(t) applied at an angle beta to the easy axis. Thermal relaxation is taken into ac count and the response of the nonequilibrium system to the infinitesim al field h(t) = h sin omegat, h perpendicular-to H, is found. The resu ltant chi(t) is studied as a function of beta, temperature, and of the frequency OMEGA of the biasing field H.