Orbit-Transfer Torque Driven Field-Free Switching of Perpendicular Magnetization

The reversal of perpendicular magnetization (PM) by electric control is crucial for high-density integration of low-power magnetic random-access memory. Although the spin-transfer torque and spin-orbit torque technologies have been used to switch the magnetization of a free layer with perpendicular magnetic anisotropy, the former has limited endurance because of the high current density directly through the junction, while the latter requires an external magnetic field or unconventional configuration to break the symmetry. Here we propose and realize the orbit-transfer torque (OTT), that is, exerting torque on the magnetization using the orbital magnetic moments, and thus demonstrate a new strategy for current-driven PM reversal without external magnetic field. The perpendicular polarization of orbital magnetic moments is generated by a direct current in a few-layer WTe2 due to the existence of nonzero Berry curvature dipole, and the polarization direction can be switched by changing the current polarity. Guided by this principle, we construct the WTe2/Fe3GeTe2 heterostructures to achieve the OTT driven field-free deterministic switching of PM.

Automated summary

This study proposes a new strategy based on orbit-transfer torque (OTT) to achieve current-driven perpendicular magnetization (PM) reversal without an external magnetic field. The perpendicular polarization of the orbital magnetic moments is generated by a direct current in a few-layer WTe2, and the polarization direction can be switched by changing the current polarity. By constructing WTe2/Fe3GeTe2 heterostructures, field-free deterministic switching of PM driven by OTT is demonstrated.