Separation of Heating and Magnetoelastic Coupling Effects in Surface-Acoustic-Wave-Enhanced Creep of Magnetic Domain Walls

Abstract

Surface acoustic waves (SAWs) have significant potential for energy-efficient control of magnetic domain walls (DWs) owing to the magnetoelastic coupling effect. However, the dissipation of radio-frequency (rf) power in a SAW device can result in heating, which can also affect the DW motion. In this work, the heating of a SAW device consisting of a $\mathrm{Pt}$/$\mathrm{Co}$/$\mathrm{Ta}$ thin film with perpendicular magnetic anisotropy in between two interdigitated transducers is measured in situ with use of an on-chip $\mathrm{Pt}$ film as a thermometer within the SAW beam path. The application of SAWs at a center frequency of 48 MHz and a total rf power of 21 dBm results in a temperature increase of approximately 10 K within the SAW beam path owing to rf-power dissipation. DW velocity in a $\mathrm{Pt}$/$\mathrm{Co}$/$\mathrm{Ta}$ thin film is evaluated separately with use of Kerr microscopy at various temperatures or in the presence of SAWs. With a 10-K increase in temperature only, the DW velocity is found to increase from $33\ifmmode\pm\else\textpm\fi{}3\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{m}/\mathrm{s}$ (at room temperature) to $104\ifmmode\pm\else\textpm\fi{}8\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{m}/\mathrm{s}$ under an external magnetic field of 65 Oe. Traveling-SAW-assisted DW velocity ($116\ifmmode\pm\else\textpm\fi{}3\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{m}/\mathrm{s}$) is slightly higher than that with a 10-K temperature increase alone, suggesting that the heating plays the major role in promoting DW motion, whereas the DW motion is significantly enhanced ($418\ifmmode\pm\else\textpm\fi{}8\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{m}/\mathrm{s}$) in the presence of standing SAWs, indicating that magnetoelastic coupling is more important than heating in this scenario.

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