Studies on Spin Ground States of Cubic-Symmetry Single-Molecule Magnets

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Recently several cube-shaped single-molecule magnets (SMM) were reported, most of which have exact cubic symmetry (Oh). The magnetic anisotropy in conventional SMMs is uniaxial and incompatible with higher point symmetry like Oh. The highly degenerate spin ground states are studied based on the classical vector picture and the giant-spin approximation.Giant spin ground states in cube-shaped SMMs were subjected to Oh quartic anisotropy, and eight or six lowest levels, which correspond to a set of equivalent classical stable directions, are well-isolated by an energy gap growing as ~S4.Fine-splitting patterns of lowest levels showed longer-period modulations with increasing 2S+1, in addition to odd-even effect expected for Kramers/non-Kramers ground states. These splittings should correspond to tunnel splitting of semiclassical giant spins trapped in the anisotropy wells.