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

## TL;DR

Researchers demonstrated a new method to control magnetization without magnetic fields using a combination of 2D magnets and topological insulators.

## Contribution

A novel heterostructure design enables deterministic, field-free spin-orbit torque switching in perpendicular magnets with high coercivity.

## Key findings

- The heterostructure combines a 2D magnet and a topological insulator to achieve field-free switching of perpendicular magnetization.
- The system exhibits a three-fold angular dependence due to wafer-scale deposition of multiple sublattices.
- The interface symmetry reduction leads to strong, deterministic switching with a coercivity of ≈1.3 T.

## 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, Cr3Te4, and a topological insulator, (Bi0.75Sb0.25)2Te3. 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 (Cs) symmetry. This synergy allows for extremely strong, field‐free SOT switching of Cr3Te4 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.

We show a giant, bias‐field free, deterministic, spin‐orbit‐torque switching of perpendicular hard magnets with HC over 1.3 T. By combining the three‐fold 3m symmetry from topological insulator surface states with the rectangular mm2 symmetry from the 2 x 1 intercalation in Cr3Te4, the interface symmetry is significantly reduced into a unidirectional m symmetry and produces the extremely strong, deterministic perpendicular switching.