Investigation of harmonic and inharmonic domain wall oscillation by sinusoidal magnetic field in the notched Permalloy nanowire using micromagnetic approach

In this work, the harmonic and inharmonic domain wall (DW) oscillations by sinusoidal magnetic field in double triangular notched Permalloy nanowires were investigated by micromagnetic simulation. The simulation results show the DW resonant frequencies were linearly related to the induced field frequency. It is shown that in the wire thickness of 2.5 nm, there is a minimum value of sinusoidal field frequency so that the DW can be harmonically oscillating as the induced magnetic field. Below the certain value, the DW will be moving out of the notch as depinning process occurs. In the higher frequency, the DW resonant frequency fluctuates and the phase-lag is larger, so that the DW oscillates inharmonically with the injected sinusoidal field and the resonant frequency decreases significantly. These phenomena could be understood by the slight change of the DW approximated mass as its position shifted around notch area. Therefore, the understanding of DW structures and dynamics under the effect of oscillating magnetic field could be a consideration on the selection of optimized nanowire geometries in the development of the domain wall-based memory storage system.