Tunneling through magnetic molecules with arbitrary angle between easy axis and magnetic field

TL;DR

This paper theoretically investigates inelastic tunneling in magnetic molecules with arbitrary orientations under strong magnetic fields, revealing complex conductance structures and orientation-dependent features.

Contribution

It introduces a comprehensive theoretical model for tunneling through magnetic molecules at arbitrary angles, including an efficient solution method and application to Mn12 molecules.

Findings

Rich fine structure in differential conductance due to arbitrary orientations.

Averaging over random orientations produces van Hove singularities.

Detailed molecular transition information can be extracted from conductance data.

Abstract

Inelastic tunneling through magnetically anisotropic molecules is studied theoretically in the presence of a strong magnetic field. Since the molecular orientation is not well controlled in tunneling experiments, we consider arbitrary angles between easy axis and field. This destroys all conservation laws except that of charge, leading to a rich fine structure in the differential conductance. Besides single molecules we also study monolayers of molecules with either aligned or random easy axes. We show that detailed information on the molecular transitions and orientations can be obtained from the differential conductance for varying magnetic field. For random easy axes, averaging over orientations leads to van Hove singularities in the differential conductance. Rate equations in the sequential-tunneling approximation are employed. An efficient approximation for their solution for complex molecules is presented. The results are applied to Mn12-based magnetic molecules.