STEPS IN THE HYSTERESIS LOOPS OF A HIGH-SPIN MOLECULE

We report the first observation of steps in the hysteresis loop of a h igh-spin molecular magnet We propose that the steps, which occur every 0.46 T, are due to thermally assisted resonant tunneling between diff erent quantum spin states. Magnetic relaxation increases dramatically when the field is in the neighborhood of a step. A simple model accoun ts for the observations and predicts a value for the anisotropy barrie r consistent with that inferred from the superparamagnetic blocking te mperature. (C) 1996 American Institute of Physics.