A three-dimensional multiscale peridynamics model for Ferroelectric/Multiferroic Tunnel Junctions

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In this project, a three-dimensional multiscale peridynamics (PD) model for fracture in ferroelectric/multiferroic tunnel junctions is proposed. A ferroelectric tunnel junction (FTJ) is a ferroelectric sandwich layer used as a barrier material between electrodes for tunneling of electrones. By using ferromagnetic electrodes the functionality of FTJs can be extended to create multiferroic tunnel junctions (MTJs). FTJs/MTJs have been widely used in electronic devices such as ferroelectric memories, microsystems, tunable microwaves, binary data storage, ferroelectric random access memories (FRAMs), among others. Fracture in FTJ/MTJs can influence their reliability. For instance, it might lead to the reduction of the electric field seen by the ferroelectric thin-film. One popular fracture mechanism in ferroelectric thin-films is caused by the polarization switching and results in a systematic loss of the remanent switchable polarization as a function of the number of bipolar switching cycles. A molecular dynamics (MD) model for FTJ/MTJs should be devised at the fine scale while a state-based thermomechanical-electromagnetic PD continuum model needs to be developed at the coarse-scale. The transfer of length scales is accomplished through higher order gradient (HOG) models of the PD and the MD models so that they show the same dynamic dispersion. The advantage of the PD model over existing models such as XFEM is its ease in handling discontinuities as they are a natural outcome of the analysis. No representation of the crack topology is needed. Moreover, due to the non-local character of the PD model, it can be coupled to the MD model in a more natural way. The approach will be verified and validated by comparison to available experimental data and used in order to answer some urgent questions related to the fracture behavior in FTJ/MTJs.