Bottom‐Stack Shear Transfer in Thin‐Film Flexoelectric Measurements

Bending‐based measurements are widely used to probe flexoelectricity in ferroelectric thin films, but the measured response is often shaped by mechanical boundary conditions beyond the intrinsic flexoelectric coefficient. Here we show that the conducting bottom stack acts as a hidden electromechanical boundary condition in mica‐supported BaTiO 3 (BTO) capacitors. Dynamic bending measurements reveal opposite bottom‐layer‐thickness dependences for two‐dimensional and oxide electrodes, while a BTO(001)/LSMO(001)/MoS 2 /mica hybrid exhibits an intermediate response at the same nominal BTO orientation as the MoS 2 ‐supported films. Interface‐resolved first‐principles calculations show that the hybrid retains a stiff BTO/LSMO contact above substantially more compliant LSMO/MoS 2 and MoS 2 /mica junctions. A reduced shear‐transfer model combines the local interface stiffnesses into an effective interfacial‐path stiffness, and finite‐element simulations confirm progressive suppression of interfacial slip with increasing tangential stiffness. These results identify the complete bottom‐stack shear‐transfer pathway as a mechanical control of bending‐induced polarization and piezoelectric admixture in ferroelectric thin‐film flexoelectric measurements.