Cotunneling spectroscopy and the properties of excited-state spin manifolds ofMn12single molecule magnets

Abstract

We study charge transport through single molecule magnet (SMM) junctions in the cotunneling regime as a tool for investigating the properties of the excited-state manifolds of neutral ${\mathrm{Mn}}_{12}$ SMs. This study is motivated by a recent transport experiment [S. Kahle et al., Nano Lett. 12, 518 (2012)] that probed the details of the magnetic and electronic structure of ${\mathrm{Mn}}_{12}$ SMMs beyond the ground-state spin manifold. A giant spin Hamiltonian and master equation approach is used to explore theoretically the cotunneling transport through ${\mathrm{Mn}}_{12}$-Ac SMM junctions. We identify SMM transitions that can account for both the strong and weak features of the experimental differential conductance spectra. We find the experimental results to imply that the excited spin-state manifolds of the neutral SMM have either different anisotropy constants or different $g$ factors in comparison with its ground-state manifold. However, the latter scenario accounts best for the experimental data.