Spin current control of magnetism

TL;DR

This paper demonstrates that ultrathin Fe films' magnetocrystalline anisotropy can be reversibly controlled by spin currents generated via the spin Hall effect in Pt, offering a new method for magnetic manipulation in spintronics.

Contribution

It introduces a novel approach to modulate magnetocrystalline anisotropy using spin currents, distinct from traditional electric-field control via gate voltages.

Findings

MCA of Fe films is reversibly modified by spin currents.

The effect depends on Fe thickness and magnetization direction.

Control is achieved through interface effects and exchange splitting modifications.

Abstract

Exploring novel strategies to manipulate the order parameter of magnetic materials by electrical means is of great importance, not only for advancing our understanding of fundamental magnetism, but also for unlocking potential practical applications. A well-established concept to date uses gate voltages to control magnetic properties, such as saturation magnetization, magnetic anisotropies, coercive field, Curie temperature and Gilbert damping, by modulating the charge carrier population within a capacitor structure. Note that the induced carriers are non-spin-polarized, so the control via the electric-field is independent of the direction of the magnetization. Here, we show that the magnetocrystalline anisotropy (MCA) of ultrathin Fe films can be reversibly modified by a spin current generated in Pt by the spin Hall effect. The effect decreases with increasing Fe thickness, indicating that the origin of the modification can be traced back to the interface. Uniquely, the change in MCA due to the spin current depends not only on the polarity of the charge current but also on the direction of magnetization, i.e. the change in MCA has opposite sign when the direction of magnetization is reversed. The control of magnetism by the spin current results from the modified exchange splitting of majority- and minority-spin bands, and differs significantly from the manipulation by gate voltages via a capacitor structure, providing a functionality that was previously unavailable and could be useful in advanced spintronic devices.