Epitaxial Co2FeSi/LiNbO3 multiferroic heterostructures with a low damping constant

Piezoelectric LiNbO
3
has been widely utilized to generate and detect spin waves in surface acoustic wave devices. Here we demonstrate an epitaxial Co-based Heusler alloy on a LiNbO
3
128° Y-cut (LN-128Y) substrate by molecular beam epitaxy. Although there is no matching between the lattice length and symmetry, the insertion of a bcc metal buffer layer enables to grow L2
1
- ordered epitaxial Co
2
FeSi films on the LN-128Y substrate. The epitaxial Co
2
FeSi/LN- 128Y multiferroic heterostructures show a high saturation magnetization of ~1235 emu/cc and a low damping constant of ~6 × 10
⁻³
. This study will open a way for an efficient electric-field control of the spin waves in surface acoustic wave devices.