  Interfacial spin to charge conversion arises due to an electric potential
perpendicular to the interface. The electric potential can be artificially
induced, for example, using ferroelectric and piezoelectric thin films at the
interface. An alternate way to induce the electric potential could be
flexoelectric field. The flexoelectricity can be observed in all the material
that either have or lack inversion symmetry, additionally no large gate bias is
needed. In this experimental study, we report large spin to charge conversion
(spin-Hall angle- 0.578) at Ni80Fe20/amorphous-Si interfaces attributed to
flexoelectricity mediated Rashba spin-orbit coupling. The flexoelectricity at
the interface also gave rise to interlayer spin-acoustic phonon or
flexo-magnetoelastic coupling. In addition to spin-charge conversion, the
strained interfaces also led to almost three-fold increase in anomalous Nernst
effect. This strain engineering for spin dependent thermoelectric behavior at
room temperature opens a new window to the realization of spintronics and
spin-caloritronics devices.
