HIGH-SPEED COHERENT SWITCHING BELOW THE STONER-WOHLFARTH LIMIT

Measurements of the switching characteristics of high coercivity magnetic tapes for field pulse widths greater than or equal to 0.6 ns have been reported previously. In an effort to develop a simple theoretical framework in which to interpret the magnetization dynamics, the well established Gilbert form of the Landau Lifshitz equation, applied to a uniaxial, single domain particle with uniform magnetization was chosen. The results which were obtained using straightforward numerical methods show that when the damping constant alpha < 1, coherent switching will sometimes occur well below the Stoner-Wohlfarth threshold. The amount of deviation which is significant over a wide range of experimentally observable parameters increases as alpha and the pulse rise time decrease. The deviation is due to the nonequilibrium condition which arises for small values of alpha and pulse rise time. The final position is always the expected Stoner-Wohlfart equilibrium position.