Tunable mode coupling in nano-contact spin torque oscillators

Recent experiments on spin-torque oscillators (STOs) have revealed interactions between multiple magnetodynamic modes, including mode coexistence, mode hopping, and temperature-driven crossover between modes. The initial multimode theory indicates that a linear coupling between several dominant modes, arising from the interaction of the subdynamic system with a magnon bath, plays an essential role in the generation of various multimode behaviors. In this work [1], we derive a set of rate equations to describe the dynamics of coupled magnetodynamic modes in a nanocontact STO, and analyze the dependence of the coupled dynamic behaviors of modes on various experimental conditions. For a minimal two-mode system, we further map the energy and phase difference of the two modes onto a 2D phase space and demonstrate in the phase portraits how the manifolds of periodic orbits and fixed points vary with external magnetic field and temperature.
[1] SZ, E. Iacocca, and O. Heinonen, Phys. Rev. Applied 8, 014034 (2017).