Spin-orbit interaction induced magnetic field, which can arise from an asymmetry of the potential well, causes imbalance of carrier densities between spin-up and spin-down electrons. In the potentiometric measurement, the detected signal follows the magnetization status of the detection ferromagnet (FM1). In case of adding the neighboring ferromagnet (FM2), the measured potential is decided by both of FMs. When the magnitude of external field is between the coercive field of the FM1 and FM2, the detector reads the intermediate potential. The detector interacts with the neighboring ferromagnet and shows four levels of potential states.