Intrinsic spin-relaxation induced negative tunnel magnetoresistance in a single-molecule magnet

TL;DR

This paper theoretically examines how intrinsic spin-relaxation influences spin-dependent transport and tunnel magnetoresistance in a single-molecule magnet, revealing suppression and sign changes of TMR under various conditions.

Contribution

It introduces a comprehensive rate-equation approach including cotunneling to analyze the impact of spin-relaxation on TMR in SMMs, highlighting conditions for negative TMR.

Findings

Fast spin-relaxation suppresses TMR in the sequential tunneling region.

External magnetic fields can induce large negative TMR with increased relaxation.

TMR can become negative at high bias voltages due to spin-relaxation effects.

Abstract

We investigate theoretically the effects of intrinsic spin-relaxation on the spin-dependent transport through a single-molecule magnet (SMM), which is weakly coupled to ferromagnetic leads. The tunnel magnetoresistance (TMR) is obtained by means of the rate-equation approach including not only the sequential but also the cotunneling processes. It is shown that the TMR is strongly suppressed by the fast spin-relaxation in the sequential region and can vary from a large positive to slight negative value in the cotunneling region. Moreover, with an external magnetic field along the easy-axis of SMM, a large negative TMR is found when the relaxation strength increases. Finally, in the high bias voltage limit the TMR for the negative bias is slightly larger than its characteristic value of the sequential region, however it can become negative for the positive bias caused by the fast spin-relaxation.