Voltage-Driven Spin-Transfer Torque in a Magnetic Particle

TL;DR

This paper explores a voltage-driven spin-transfer torque device using magnetic particles or molecules, demonstrating that magnetization can be manipulated electronically with minimal power, relying on critical voltage rather than current.

Contribution

It introduces a novel spin-transfer torque mechanism driven by voltage in magnetic particles or molecules, reducing power dissipation and enabling efficient magnetization control.

Findings

Magnetization switching is governed by a critical voltage, not current.

Spin-orbit energy shifts influence the critical voltage.

Device enables low-power magnetic state manipulation.

Abstract

We discuss a spin-transfer torque device, where the role of the soft ferromagnetic layer is played by a magnetic particle or a magnetic molecule, in weak tunnel contact with two spin polarized leads. We investigate if the magnetization of the particle can be manipulated electronically, in the regime where the critical current for magnetization switching is negligibly weak, which could be due to the reduced particle dimensions. Using master equation simulations to evaluate the effects of spin-orbit anisotropy energy fluctuations on spin-transfer, we obtain reliable reading and writing of the magnetization state of such magnetic particle, and find that the device relies on a critical voltage rather than a critical current. The critical voltage is governed by the spin-orbit energy shifts of discrete levels in the particle. This finding opens a possibility to significantly reduce the power dissipation involved in spin-transfer torque switching, by using very small magnetic particles or molecules.