Researchers achieve field‑free switching of hard ferromagnets with giant spin‑orbit torque
Researchers at the University of Waterloo recently demonstrated fully electrical, field‑free control of perpendicular magnetization using spin‑orbit torque (SOT) in a low‑symmetry 2D magnet/topological‑insulator heterostructure, paving the way for scalable, energy‑efficient spintronic memory and logic devices.
Stacking the three-fold symmetry of BiSbTe on top of the two-fold symmetry of intercalated-CrTe, the interface only permits a unidirectional symmetry which produces an extremely strong out-of-plane spin torque and can deterministically switch a very hard, perpendicular magnet with ease. Image credit: University of Waterloo
Modern MRAM and related spintronic memories need dense, robust perpendicular magnetic anisotropy (PMA) bits that can be switched deterministically with low energy consumption, but conventional SOT easily switches only in‑plane moments and typically requires an external bias field to tilt perpendicular spins “up” or “down”. In perpendicular configurations, bits point out of the film plane, which boosts storage density but makes the energy‑efficient, fully electrical control of their state difficult. Standard heavy‑metal/ferromagnet stacks already break out‑of‑plane symmetry and can support in‑plane switching, yet deterministic out‑of‑plane reversal demands breaking additional in‑plane symmetries - usually via an applied magnetic field, which adds circuit complexity, power overhead, and risks cross‑talk between neighboring bits.
