How a Light Metal Twists Magnetism express
Usually, to flip a magnet in a memory device, heavy metals like platinum or tungsten are used. When current flows, their electrons are deflected sideways, like a crowd on an escalator, and this deflection imparts a rotational torque to the magnetic layer. But heavy metals are expensive and lose a lot of energy as heat.
Now researchers have replaced the heavy metal with a light one — vanadium nitride (VN). Here, a different mechanism is at play: the orbital Hall effect. Electrons in VN don't just fly; they move in orbits, like planets around the Sun. When current flows, the orbits tilt, and this tilt is transferred to the adjacent [Co/Pt]3 layer, where it becomes a conventional spin torque. That torque flips the magnetization.
Full switching required a current density of about 10⁷ A/cm² and an external magnetic field. Without the field, switching was only partial. The current density is comparable to tungsten-based devices, but the material itself is lighter and potentially cheaper. Calculations confirmed that VN has large orbital conductivity and small spin conductivity, meaning the orbital current indeed dominates.
This approach could underpin a new type of electronics—'orbitronics'—where information is carried by orbital angular momentum rather than spin or charge. It opens the door to more economical memory and logic devices.
Original abstract
as written by the authors arXiv:2601.01115
The orbital Hall effect (OHE) in light transition metals offers a promising route to generate orbital torques for efficient magnetization control, providing an alternative to conventional spin Hall effect approaches that rely on heavy metals. We demonstrate perpendicular magnetization switching in [Co/Pt]3 multilayers driven by the OHE in a light 3d transition metal nitride, VN, with 111-texture of face-center cubic structure. Second harmonic Hall measurement reveals a large torque efficiency of -0.41 in the VN(7.5 nm)/[Co(0.35nm)/Pt(0.3 nm)]3, which significantly surpasses that in the control samples with Co, Py, and CoFeB ferromagnets, suggesting strong conversion of orbital current originating from VN to spin current by [Co/Pt]3 ferromagnet. Full switching by in-plane current is achieved with an in-plane magnetic field, while partial field-free switching occurs without it. The critical current density for the switching is found to be comparable to that of the W-based spin-orbit torque device. First-principles calculations confirm a large orbital Hall conductivity in VN, with a small spin Hall conductivity around the Fermi energy. Our results highlight the potential in the combination of light 3d transition metal nitrides and Co/Pt ferromagnetic multilayer with 111-texture to maximize the magnetization switching efficiency of orbitronic devices.
Vanadium nitride is nearly as hard as steel but conducts electricity almost like a metal, so it's used in wear-resistant coatings and, as it turns out, in spintronics.