RESONANT-TUNNELING OF MAGNETIZATION IN MN-12 ACETATE COMPLEX

Based on low-temperature measurements on oriented crystallites of Mn-1 2 acetate complex, we report strong evidence for resonant tunneling of magnetization for these high spin molecules: we observed periodic ste ps in the hysteresis loops, periodic marked peaks in the magnetic rela xation rate at the fields corresponding to these steps, and a concomit ant periodic decrease of the blocking temperature with magnetic field. WE attribute these observations to thermally assisted resonant tunnel ing of the magnetization in a double well potential and propose a deta iled model to account for our results.