Excitation and detection of short-waved spin waves in ultrathin Ta/CoFeB/MgO-layer system suitable for spin-orbit-torque magnonics

Abstract

We report on the excitation and detection of short-waved spin waves with wave vectors up to about $40\,\mathrm{rad}\,\mu\mathrm{m}^{-1}$ in spin-wave waveguides made from ultrathin, in-plane magnetized Co$_{8}$Fe$_{72}$B$_{20}$ (CoFeB). The CoFeB is incorporated in a layer stack of Ta/CoFeB/Mgo, a layer system featuring large spin orbit torques and a large perpendicular magnetic anisotropy constant. The short-waved spin waves are excited by nanometric coplanar waveguides and are detected via spin rectification and microfocussed Brillouin light scattering spectroscopy. We show that the large perpendicular magnetic anisotropy benefits the spin-wave lifetime greatly, resulting in a lifetime comparable to bulk systems without interfacial damping. The presented results pave the way for the successful extension of magnonics to ultrathin asymmetric layer stacks featuring large spin orbit torques.