Field-free spin hall oscillator based on giant magnetoresistance effect and its potential for electrical synchronization.

Spin Hall nano oscillators (SHNOs) have attracted much attention in recent years due to their great potential for applications in neuromorphic computation. However, the output power of SHNOs is very low and an external magnetic field is required to generate microwave signal continuously, which hinders the further development of SHNOs. In order to solve the two problems, we propose a new-type SHNO based on the giant magnetoresistance (GMR) effect, while retaining the advantage of the simple fabrication process of the conventional oscillator. The huge magnetoresistance ratio provided by the GMR effect can increase the power of this novel oscillator by several orders of magnitude. In addition, by designing the magnetization easy axis of the free and reference layers in the GMR film layers, this novel oscillator can operate effectively without the need of and external magnetic field. Furthermore, we have preliminarily investigated the feasibility of electrical synchronization in the field of SHNOs from the perspective of microspin simulation and found that parallel connection can provide stronger coupling strength compared with series connection. Our research solves the core problems that currently hinder the further development of SHNOs, facilitating the realization and application of large-scale synchronized array of SHNOs.