Field‐Free, Deterministic Giant Spin‐Orbit Torque Switching of 1.3 T Perpendicular Magnetization With Symmetry‐Lifted Topological Surface States

Abstract

ABSTRACT The field‐free control of perpendicular magnetization using spin‐orbit torque (SOT) is a key challenge in spintronics, simplifying design and integration for both memory and logic applications. Unlike conventional heavy metal/ferromagnet heterostructures that already break out‐of‐plane symmetry, thus can readily offer in‐plane switching, realizing deterministic out‐of‐plane switching requires breaking additional in‐plane symmetries. In this study, we demonstrate field‐free switching in a heterostructure composed of a self‐intercalated 2D magnet, Cr 3 Te 4 , and a topological insulator, (Bi 0.75 Sb 0.25 ) 2 Te 3 . In this system, the surface states of the topological insulator ensure efficient charge‐to‐spin conversion, but not deterministic on its own. The ordered 2 × 1 self‐intercalation of the perpendicular magnet provides additional symmetry breaking on the interface, rendering a combined unidirectional m (C s ) symmetry. This synergy allows for extremely strong, field‐free SOT switching of Cr 3 Te 4 with perpendicular coercivity ≈1.3 T. Unlike exfoliated 2D materials that tend to be single‐crystal, our wafer‐scale deposition naturally nucleates three equivalent types of 2 × 1 sublattices, and therefore the combined SOT switching manifests an apparent three‐fold angular dependence. These findings highlight a promising pathway toward efficient, topological insulator‐based spintronic device and material engineering.