Mechanical switching in ferroelectrics by shear stress and its implications on charged domain wall generation and vortex memory devices

Abstract

Recently, the resurgence of interest in flexoelectricity in solids has promoted research on switching of ferroelectric domains via mechanical loads. In this work, combining thermodynamic calculation and phase-field simulation, we revealed that mechanical switching of polarization can be achieved in ferroelectrics by shear stress via a simple mechanism where the presence of flexoelectricity is not necessary. The switching is a consequence of the trilinear coupling between shear stress and the two polarization components that lie in the shear strain plane. Specifically, when the direction of one polarization component is fixed, switching of the other component can be induced by applying a shear stress. Moreover, when the shear stress is fixed, switching of one of the polarization components can lead to the switching of the other component. Phase diagrams of the stable polarization state as a function of shear stress, temperature and electric field are calculated. Furthermore, as demonstrated by phase-field simulation on a ferroelectric thin film, domain switching can indeed be realized by a local shear stress. Importantly, the combining effect of shear stress and electric field can lead to a deterministic writing of charged domain walls, which should be very useful for the fabrication of domain wall devices. The implication of such a shear-stress-modified polarization switching on the design of vortex memory device is also discussed.