Bias-voltage-controlled interlayer exchange coupling

We propose a new system whose magnetization direction can be controlled by an applied bias voltage without an external magnetic field. The system consists of a four layered structure F-1/S/I/F-2 (F-1, F-2: ferromagnets, S: spacer, I: insulator), An analytic expression for bias-voltage-controlled interlayer exchange coupling in this system is developed within a simple free-electron-like, one-dimensional approximation, According to the approach, the magnetic configurations of the two magnetic layers oscillate from antiferromagnetic to ferromagnetic with applied bias voltage. This implies that we can switch/rotate the magnetization direction without an external magnetic field. Possible applications of such a system are also discussed.