Transport through anisotropic magnetic molecules with partially ferromagnetic leads: Spin-charge conversion and negative differential conductance

TL;DR

This paper models inelastic transport through anisotropic magnetic molecules with ferromagnetic leads, revealing spin blockade, negative differential conductance, and spin-charge conversion effects that are relevant for molecular spintronics.

Contribution

It introduces a theoretical framework for understanding spin blockade and negative differential conductance in magnetic molecules with ferromagnetic contacts, highlighting spin-charge conversion capabilities.

Findings

Current suppression due to spin blockade over wide voltage ranges

Negative differential conductance observed at low and room temperatures

Strong dependence of transmitted charge on initial spin state

Abstract

We theoretically investigate inelastic transport through anisotropic magnetic molecules weakly coupled to one ferromagnetic and one nonmagnetic lead. We find that the current is suppressed over wide voltage ranges due to spin blockade. In this system, spin blockade is associated with successive spin flips of the molecular spins and depends on the anisotropy energy barrier. This leads to the appearance of a window of bias voltages between the Coulomb blockade and spin blockade regimes where the current is large and to negative differential conductance at low temperatures. Remarkably, negative differential conductance is also present close to room temperature. Spin-blockade behavior is accompanied by super-Poissonian shot noise, like in nonmagnetic quantum dots. Finally, we show that the charge transmitted through the molecule between initial preparation in a certain spin state and infinite time very strongly depends on the initial spin state in certain parameter ranges. Thus the molecule can act as a spin-charge converter, an effect potentially useful as a read-out mechanism for molecular spintronics.