Pulse-width Dependent Critical Current Density and the Depinning Probability of a Magnetic Skyrmion by Spin-Polarized Currents

Magnetic skyrmions are topological spin textures with potential applications in future spintronic devices. Spin -polarized current is an effective way to manipulate magnetic skyrmions. Recent experiments show that the critical current density to move the skyrmion decays gradually with the pulse width [Wang et al., Nat. Commun. 13, 1593 (2022)]. In this work, we numerically studied the critical current density of the skyrmion depinning in the presence of currents. In the framework of the Thiele equation, the current density plays a role as the potential that acts on the skyrmion. In the limit of zero damping, the system reduces to a Hamiltonian system even in the presence of current. Thus the induced potential due to the disorders determines the critical current density. The temperature enhances the skyrmion depinning process, which depends on the current density and the pulse width. The mean first passage time for the skyrmion depinning is calculated using the finite element method, which explains the inverse relation between the current density and the pulse width.