Spin transport and tunable Gilbert damping in a single-molecule magnet junction

TL;DR

This paper investigates spin transport and tunable Gilbert damping in a single-molecule magnet junction, revealing how electronic interactions influence magnetic dynamics and how damping can be controlled electrically.

Contribution

It introduces a theoretical framework for analyzing spin currents and damping in a molecular junction with precessing magnetization, highlighting tunable damping mechanisms.

Findings

Gilbert damping coefficient is controllable by bias, gate voltages, and magnetic field.

Inelastic tunneling processes contribute to spin currents and torque.

Damping exhibits non-monotonic dependence on tunneling rates.

Abstract

We study time-dependent electronic and spin transport through an electronic level connected to two leads and coupled with a single-molecule magnet via exchange interaction. The molecular spin is treated as a classical variable and precesses around an external magnetic field. We derive expressions for charge and spin currents by means of the Keldysh non-equilibrium Green's functions technique in linear order with respect to the time-dependent magnetic field created by this precession. The coupling between the electronic spins and the magnetization dynamics of the molecule creates inelastic tunneling processes which contribute to the spin currents. The inelastic spin currents, in turn, generate a spin-transfer torque acting on the molecular spin. This back-action includes a contribution to the Gilbert damping and a modification of the precession frequency. The Gilbert damping coefficient can be controlled by the bias and gate voltages or via the external magnetic field and has a non-monotonic dependence on the tunneling rates.