Switching of a quantum dot spin valve by single molecule magnets

Abstract

We explore theoretically the spin transport in nanostructures consisting of a gold quantum dot bridging nonmagnetic electrodes and two Mn${}_{12}$-Ph single molecule magnets (SMMs) that are thiol bonded to the dot but are not in direct contact with the electrodes. We find that reversal of the magnetic moment of either SMM by the application of a magnetic field leads to a large change in the resistance of the dot, i.e., a strong spin-valve effect. We show that this phenomenon arises from the following physical principle: The spin-dependent molecular orbitals that extend over the dot and both SMMs change drastically when the magnetic moment of either SMM is reversed, resulting in a large change in the conduction via those orbitals. The same physics may also be responsible for the spin-valve phenomena discovered recently in carbon nanotube quantum dots with rare-earth SMMs [M. Urdampilleta et al., Nat. Mater. 10, 502 (2011)].