  Artificial modulation of a neuronal subset through ion channels activation
can initiate firing patterns of an entire neural circuit in vivo. As nanovalves
in the cell membrane, voltage-gated ion channels can be artificially controlled
by the electric field gradient that caused by externally applied time varying
magnetic fields. Herein, we theoretically investigate the feasibility of
modulating neural activities by using magnetic spintronic nanostructures. An
antiferromagnet/ferromagnet (AFM/FM) structure is explored as neuromodulator.
For FM layer with perpendicular magnetization, stable bidirectional
magnetization switching can be achieved by applying in-plane currents through
AFM layer to induce the spin-orbit torque (SOT) due to the spin Hall effect
(SHE). This Spin-orbit Torque Neurostimulator (SOTNS) utilizes in-plane charge
current pulses to switch the magnetization in FM layer. The time changing
magnetic stray field induces electric field that modulates the surrounding
neurons. The Object Oriented Micromagnetic Framework (OOMMF) is used to
calculate space and time dependent magnetic dynamics of SOTNS structure. The
current driven magnetization dynamics in SOTNS has no mechanically moving
parts. Furthermore, the size of SOTNS can be down to tens of nanometers, thus,
arrays of SOTNSs could be fabricated, integrated together and patterned on a
flexible substrate, which gives us much more flexible control of the
neuromodulation with cellular resolution.
