Ideal memristor based on viscous magnetization dynamics driven by spin torque*

We use analytical calculations and simulations to show that ideal memristors - devices whose resistance is proportional to the charge that flows through them - can be realized using spin torque-driven viscous magnetization dynamics. The large damping required for the viscous dynamics can be achieved by utilizing the spin liquid state in F/AF heterostructures, where spin glass and spin liquid states emerge due to the frustration of exchange interaction [1,2]. The viscosity, and thus the memristive response, is tunable by proximity to the glass transition.
We also show that Joule heating facilitates nonvolatile operation, and provides second-order memristive functionality to the proposed memristors, with temperature serving as an extra state variable. The variation of temperature, similar to the increase and spontaneous decay of Ca²⁺ ion in neural synapses, provides a mechanism for encoding the timing information of current spikes into the variations of synaptic weights, enabling the implementation of spike timing-dependent plasticity in spintronic neuromorphic networks.
[1] T. Ma, S. Urazhdin Phys. Rev. B 97, 054402 (2018).
[2] S. Urazhdin, W.Li, L. Novozhilova J. Magn. Magn. Mater. 476, 75-85 (2019)