QUANTUM TUNNELING OF MAGNETIZATION IN MN-12 ACETATE CLUSTERS

The Mn cluster complex [Mn12O12(CH3COO)(16)(H2O)(4)] . 2CH(3)COOH . 4H (2)O exhibits macroscopic quantum tunneling of magnetic moment, as evi denced by pronounced steps in the magnetization curve at low temperatu res. The magnetization of Mn-12 acetate single crystals, and the slow relaxation of the magnetic moment, was measured in the temperature ran ge from 3 K down to 60 mK with a very sensitive cantilever magnetomete r. The relaxation of the magnetic moment, at low temperatures and for magnetic fields near a step in the magnetization curve, is logarithmic and shows a complicated temperature dependence. In contrast, other in vestigations had found a temperature-independent relaxation, with a re laxation time saturated at 10(8) s. (C) 1998 Elsevier Science B.V. All rights reserved.