Octonary Resistance States in La_0.7Sr_0.3MnO₃/BaTiO₃/La_0.7Sr_0.3MnO₃ Multiferroic Tunnel Junctions

General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La_0.7Sr_0.3MnO₃/BaTiO₃/La_0.7Sr_0.3MnO₃ junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45° and 90°) magnetic configurations. Combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO₃ barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.