Large-amplitude and widely tunable self-oscillations enabled by the inertial effect in uniaxial antiferromagnets driven by spin-orbit torques

Recently, the inertia has been demonstrated for magnetization dynamics, such as the nutational resonance and spin wave, as well as the inertial switching. Here, we focus on the inertial effect of self-oscillations induced by the spin-orbit torques in easy-axis antiferromagnets. Utilizing the stability analysis of equilibria and the exact solution of precession, we analytically construct the phase diagram controlled by the current and the inertial relaxation time. We then show that the magnetic inertia expands the tunable range of oscillation, the frequency of which is in the terahertz regime. Meanwhile, the frequency is proportional to the current and can enter an ultrahigh regime. Particularly, a lager-amplitude oscillation always persists when increasing the current. These features stand in sharp contrast to the case without an inertia, for which the amplitude of oscillation decreases with an increasing current and the oscillation fades away beyond a critical current. Our results not only enrich the nonlinear magnetic dynamics involving the inertial effect but also provide guidelines for the terahertz application of antiferromagnetic spintronics.