Giant tunneling electroresistance (up to $\sim $10,000{\%}) in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/BaTiO$_{3}$/La$_{0.5}$Ca$_{0.5}$MnO$_{3}$/La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ ferroelectric tunnel junctions

Tunnel junction with a Ferroelectric (FE) barrier (FTJ) presents an opportunity for nanoelectronics because of the bi-stable electric field control of the tunneling resistance. FTJs of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/BaTiO$_{3}$/La$_{0.5}$Ca$_{0.5}$MnO$_{3}$/La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ have been fabricated with pulsed-laser deposition. The special feature in the FTJ design is to insert an ultrathin (0.4 - 1.2 nm) La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ film between La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ Ferromagnetic (FM) electrode and BaTiO$_{3}$ FE barrier. A giant and reproducible tunneling electroresistance effect ($\sim $10,000{\%}) was obtained with the reversal of FE polarization, about two orders of magnitude larger than the similar sized FTJ without the inserted La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ layer. This result is consistent with the theoretical prediction [PRL 106, 157203 (2011)] that at a BaTiO$_{3}$/La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ interface, an anti-FM insulating - FM metallic phase transition can occur in La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ when the polarization of the BaTiO$_{3}$ is reversed due to the interfacial charge doping effect.