MAGNETIC-PROPERTIES OF A MN CLUSTER ORGANIC-COMPOUND

We describe unusual magnetic properties of a 12 Mn cluster organic com pound that has a S = 10 ground state and a very high anisotropy. Ac su sceptibility and magnetization measurements on powder samples show a s uperparamagnetic like behavior, with relaxation times following tau = tau(0) exp(Delta/T), where tau(0) similar to 10(-7) s. Field cooled an d zero field cooled magnetization curves split below 3 K, with onset o f hysteresis. Low temperature specific heat measurements show no anoma ly down to 1.6 K. The isolated and well-defined dusters form an excell ent model system for magnetic relaxation studies and possible quantum tunneling effects at very low temperatures.