Nonvolatile FFs (NVFFs) have attracted great interests for power-gating applications and a variety of NVFFs have been proposed by integrating nonvolatile memory devices. Nevertheless, the mainstream spin transfer torque effect based magnetic tunnel junction switching approach still consumes much dynamic power and long delay. The spin-orbit torque effect provides an alternative approach for high-speed and low-power MTJ switching, therefore rather promising for NVFF design. In this work, we propose four NVFF designs based on the FF architectures (either DFF or SRFF). The circuit structures and operations are investigated, and the performance is evaluated at 40 nm technology node.