Highly Nonreciprocal Spin Waves Excited by Magnetoelastic Coupling in a Ni/Si Bilayer

We demonstrate a largely enhanced nonreciprocal propagation of spin waves (SWs) magnetoelastically excited in Ni/Si bilayer films. The nonreciprocity is attributed to the shear component of the strain tensor, which can be enlarged by increasing the thickness of the Si layer. By evaporating a 400-nm-thick Si layer on a Ni film, we enhanced the nonreciprocal ratio by up to 1200%. This finding paves the way for rectification of SWs in magnonic devices.