Probing spin frustration in high-symmetry magnetic nanomolecules by inelastic neutron scattering

Abstract

Low temperature inelastic neutron scattering studies have been performed to characterize the low energy magnetic excitation spectrum of the magnetic nanomolecule ${{\mathrm{Mo}}_{72}{\mathrm{Fe}}_{30}}$. This unique highly symmetric cluster features spin frustration and is one of the largest discrete magnetic molecules studied to date by inelastic neutron scattering. The $30\phantom{\rule{0.3em}{0ex}}\mathrm{s}=5∕2$ ${\mathrm{Fe}}^{\mathrm{III}}$ ions, embedded in a spherical polyoxomolybdate molecule, occupy the vertices of an icosidodecahedron and are coupled via nearest-neighbor antiferromagnetic interactions. The overall energy scale of the excitation and the gross features of the temperature dependence of the observed neutron scattering are explained by a quantum model of the frustrated spin cluster. However, no satisfactory theoretical explanation is yet available for the observed magnetic field dependence.