  Single-molecule transistors provide a unique experimental tool to investigate
the coupling between charge transport and the molecular degrees of freedom in
individual molecules. One interesting class of molecules for such experiments
are the single-molecule magnets, since the intramolecular exchange forces
present in these molecules should couple strongly to the spin of transport
electrons, thereby providing both new mechanisms for modulating electron flow
and also new means for probing nanoscale magnetic excitations. Here we report
single-molecule transistor measurements on devices incorporating Mn12
molecules. By studying the electron-tunneling spectrum as a function of
magnetic field, we are able to identify clear signatures of magnetic states and
their associated magnetic anisotropy. A comparison of the data to simulations
also suggests that electron flow can strongly enhance magnetic relaxation of
the magnetic molecule.
