Large magnetoelectric effect in organic ferroelectric copolymer-based multiferroic tunnel junctions

We report electrically controlled interfacial spin polarization, or the magnetoelectric effect in multiferroic tunnel junctions by employing organic ferroelectric copolymers, poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFE)), as a tunneling barrier. First, we show that the ferroelectric domains and spontaneous ferroelectric polarization of the P(VDF-TrFE) films can be formed in a thin interlayer. Next, we demonstrate that the tunneling magnetoresistance in the unpolarized multiferroic tunnel junction severely quenches from 21% at 20 K to 0.7% at 296 K. Remarkably, we find that the interfacial spin polarization of the device, dubbed spinterface, can be gradually tuned by controlling the ferroelectric polarization with an applied electric field. Specifically, the tunneling electromagnetoresistance can reach around 1000% while the tunneling electroresistance reaches about 30% at 200 K. We speculate that the interface might act as a polarization-dependent spin filter causing the large spinterface effect. The result suggests that organic magnetoelectric-based information storage with four-state bits is feasible at room temperature.