Spin Rectification and Electrically Controlled Spin Transport in Molecular-Ferroelectrics-Based Spin Valves

We report a spin-rectification effect in a spin-valve structure consisting of ferroelectric croconic acid (${\mathrm{C}}_{5}{\mathrm{H}}_{2}{\mathrm{O}}_{5}$) sandwiched between ferromagnetic electrodes ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{Mn}\mathrm{O}}_{3}$ and $\mathrm{Co}$, which can be switched between a high-resistance (off) and a low-resistance (on) state by a poling voltage. In the off state, the magnetoresistance (MR) sign reverses with the measurement voltage with a 0.1-V offset, suggesting a spin-rectification behavior, while in the on state the MR remains negative. These observations can be understood in terms of electrically controlled interfacial energy-band alignment either from the electrostatic effect or from the interfacial redox process. The observed spin-rectification effect suggests the possibility of diodelike devices for spin-polarized current.