Assessment of the anisotropy in the molecule Mn19 with a high-spin ground state S=83/2 by 35 GHz electron paramagnetic resonance

35 GHz electron paramagnetic resonance experiments on a powder sample of the magnetic molecule Wig with a high-spin ground state S = 83/2 are presented. At low temperatures, the data are well described by the simulated spectra for an isolated spin with a zero-field-splitting parameter D = 0.004 cm(-1), which is, in particular, positive. Hence, Mn-19 is not a single-molecule magnet; the previously observed magnetic hysteresis at ultralow temperatures is likely due to intermolecular dipolar interactions.