Spintronic Oscillators, Their Synchronization Properties, and Applications in Oscillatory Neural Networks (ONNs)

In this chapter, we first discuss the operating principle of the spin Hall nano-oscillator (SHNO) and then discuss how auto-oscillation of the magnetic moments in it can be modelled using the macro-spin model (Landau–Lifschitz–Gilbert–Slonczweski (LLGS) equations) and micromagnetic model discussed earlier in the book. Next, we discuss how multiple SHNOs can be synchronized using dipole field, spin waves, electrical coupling, etc., and review some experimental demonstrations. Next, we discuss the modelling of dipole-coupled SHNOs, in the nanopillar geometry, using coupled LLGS equations and show their synchronization behaviour. We also briefly discuss modelling (following micromagnetic framework) and experimental demonstrations of spin-wave-coupled SHNOs and their synchronization behaviour. Finally, we discuss applications of this synchronization scheme in neuromorphic computing.