Stochastic dynamics of skyrmions and domain walls on the racetrack: Impact of equilibrium and nonequilibrium noise
Dr. Anton Hlushchenko, Kharkiv Institute of Physics and Technology, Kharkiv, Ukraine

Date, Time
30.10, 15:00 - 16:00

Current-driven motion of domain walls and skyrmions is of key importance for the operation of non-volatile memory devices. The motion of both skyrmions and domain structures is driven by the same spin transfer mechanism, and racetrack memory requires the creation of current densities to achieve velocities of about 10–100 m/s, which is necessary for applications. High speed applications require higher current density, which results in increased spin current noise in the system. We provide a detailed description of the influence of equilibrium (thermal) and nonequilibrium (spin current) noise on the skyrmion dynamics. Our approach is based on the stochastic Thiele equation that takes into account both random sources. It allows us to derive diffusion coefficients describing the influence of equilibrium and nonequilibrium fluctuations and obtain mean squared displacement (MSD) as a function of time. Our theoretical analysis and micromagnetic simulations demonstrate dominance of the spin current noise in typical racetrack samples up to the room temperatures. We also consider first passage time (FPT) problem for the skyrmion motion on the racetrack and calculate mean FPT and its standard deviation along and across the racetrack. The stochasticity of the motion of magnetic textures is of importance for their stability and detection on the racetracks.