Magnetization switching remains one of the central applications of spintronic devices.
"Useful devices, such as magnetic memory or logic circuits, require the ability to switch individual magnetic bits without disturbing neighboring ones," explains Mehrdad Elyasi, a member of AIMR. "This means technologically relevant solutions must not require global magnetic fields or high-power current inputs to achieve localized deterministic switching."
To this end, a promising approach uses quasiparticles called magnons—wave-like magnetic disturbances that, in principle, can be confined, guided, or even generated locally, particularly using patterned nanostructures or pulsed excitations.
However, recent work on materials with perpendicular magnetic anisotropy (PMA)—ideal for high-density memory—showed that magnons could only switch magnetization reliably in the presence of an external magnetic field.
To overcome this, researchers needed a way to produce a controlled, out-of-plane spin-polarized magnon currents strong enough to deterministically switch PMA materials—without relying on external fields.
In a 2024 article published in Nature Nanotechnology, Elyasi and co-workers addressed this challenge by exploiting the crystal symmetry and spin canting angle of WTe2 to generate the desired magnon torque in a WTe2/NiO/CoFeB heterostructure1. The team used the low symmetry of WTe2 to produce spin-polarized electrons with both in-plane and out-of-plane components, which were injected into the adjacent NiO layer. The NiO antiferromagnetic insulator then converted the spin current into magnon currents, preserving their original polarization direction—a slight out-of-plane canting angle of approximately 8.5°.
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