Changing Exchange Bias in Spin Valves with an Electric Current

TLDR

Spin transfer enables electrical currents to impart spin angular momentum to ferromagnets, offering precise spatial and temporal control of magnetic states and promising applications in memory and recording, and recent theory predicts that this effect can also occur in antiferromagnets and may even be stronger under certain conditions. This study demonstrates spin angular momentum transfer across a ferromagnet/antiferromagnet interface. The effect is driven by a high‑density current (~10¹² A m⁻²) and observed through changes in the exchange bias at the interface. The exchange bias can be increased or decreased depending on current polarity, a result consistent with a spin‑polarized current exerting torque on antiferromagnetic moments, and this controllability could be exploited to switch spin‑valve devices for memory applications.

Abstract

An electrical current can transfer spin angular momentum to a ferromagnet. This novel physical phenomenon, called spin transfer, offers unprecedented spatial and temporal control over the magnetic state of a ferromagnet and has tremendous potential in a broad range of technologies, including magnetic memory and recording. Recently, it has been predicted that spin transfer is not limited to ferromagnets, but can also occur in antiferromagnetic materials and even be stronger under some conditions. In this paper we demonstrate transfer of spin angular momentum across an interface between ferromagnetic and antiferromagnetic metals. The spin transfer is mediated by an electrical current of high density (~10^12 A/m^2) and revealed by variation in the exchange bias at the ferromagnet/antiferromagnet interface. We find that, depending on the polarity of the electrical current flowing across the interface, the strength of the exchange bias can either increase or decrease. This finding is explained by the theoretical prediction that a spin polarized current generates a torque on magnetic moments in the antiferromagnet. Current-mediated variation of exchange bias can be used to control the magnetic state of spin-valve devices, e.g., in magnetic memory applications.