Chaos in spin-torque oscillator with feedback circuit

This is the authors' abstract. We don't add key points for this paper.

Excitation of chaotic magnetization dynamics in nanomagnets is of great interest because it bridges the condensed matter physics and nonlinear science and has a potential to emerging technologies such as neuromorphic computing. However, it has been difficult to observe and identify chaos in spintronics devices because the excitation of chaos requires dynamics in a large-dimensional phase space, according to the Poincar\'e-Bendixson theorem. An efficient way to overcome this issue is using feedback, which enables the dynamical degrees of freedom to be increased even in a single device. Here, we experimentally demonstrate the excitation of chaos in a vortex spin-torque oscillator by utilizing a feedback circuit. The radio-frequency current emitted by the oscillator flows in the feedback circuit and is converted into an oscillating magnetic field. The oscillating field generates a torque acting on the vortex and modulates its dynamics, resulting in chaotic dynamics which can be tuned by electrical means.