Nanomagnetic Gears With Electrically Controlled Transmission Ratio

Magnetic gears offer a reliable, low-maintenance, efficient, and vibration-free alternative to traditional mechanical gears. At the micro- and nanoscale, electrical manipulation of magnetic domains can further enhance the performance and versatility of these gears. In this work, we introduce the concept of spintronic magnetic nanogears which are scalable solutions which exhibit an electrical continuously adjustable transmission ratio between the two gear rotors by employing as driving mechanics the spin-orbit torque. We have analyzed the coupling of magnetic domains in two parallel circular nanotracks, each serving as a rotor in the gear system, using experimentally determined material parameters. We notice that to current densities J up to 4.1012 A/m2 and distances up to 30 nm, the magnetic domains remain fully coupled via stray fields. By exploiting the current-driven motion of the magnetic domains, we derive a transmission ratio given by ω2/ω1 = 1 + ωd/ω1 where ω2 and ω1 are the angular velocities of the driven and driver rotors, respectively, and ωd(J) is the current driven angular velocity of the magnetic domains. This work paves the way for the development of a new generation of highly tunable nanomagnetic gears with potential applications in nano-actuators, micromachines and other nanoscale devices.