Domain walls (DWs) in thin films with perpendicular magnetic anisotropy (PMA) are promising information carriers for the next generation of data storage and logic operation devices. 1,2 However, controlling DW motion efficiently remains unsolved. Here, we experimentally demonstrated an enhanced DW velocity in a PMA film using both standing and travelling surface acoustic waves (SAWs). Two interdigitated transducers (Fig.1a), centre frequency 47.93 MHz (Fig. 1b), were patterned on opposite side of a Ta(5)/Pt(2.5)/Co(0.5)/Ta(5) film (thicknesses in nm). The film was dc magnetron sputtered onto a lithium niobate substrate. Kerr microscopy was used to measure the DW velocity by measuring the DW displacement due to a pulsed field. Results showed that DW velocity increased from 7±1 to 34±1 µm/s with an increasing magnetic field from 10.9 to 14.8 Oe without SAWs (Fig.1c). A significant DW velocity increase can be observed in the presence of the standing SAW (Fig.1c) with applied SAW power from 15.5 to 20.5 dBm. An up to 24-fold DW velocity increase (870±10 µm/s at 14.8 Oe) can be found in the presence of standing SAWs at 20.5 dBm compared to that without SAW at the same field. A less significant DW increase (372±6 µm/s at 14.8 Oe) can also be observed with the application of travelling SAWs (Fig.1d). SAWs locally and periodically lower and raise the anisotropy of the thin film due to the magnetoelastic coupling effect, temporarily assisting the DW to overcome pinning energy barriers during its motion. 3,4 This process is possibly an accumulative effect, which can explain the velocity difference between results for the travelling and standing SAW. This study demonstrates the potential for SAWs to efficiently manipulate magnetic DWs.
References
1 Marathe et al. Vacuum, 14, 329, (2017)
2 Li et al., J. Appl. Phys, 115, 17E307 (2014)
3 Shepley Sci. Rep. 5, 7921 (2015)
4 Shuai et al. Appl. Phys. Lett. 120, 252402 (2022)

Fig. 1 (a) Experimental set-up; (b) S-parameters of the SAW device; (c) Domain wall velocity against the applied field with standing SAWs (various applied SAW power) and without SAW. (d) Domain wall velocity against the applied field without SAW and with standing/travelling SAWs (applied SAW power of 20.5 dBm).