Langevin magnetic sensor using perpendicular anisotropic CoFeB/MgO/CoFeB tunneling junction with ferromagnetic and superparamagnetic CoFeB layers

Magnetic field sensors utilizing tunneling magnetoresistance (TMR) effect often consists of two ferromagnetic layers with orthogonal anisotropy in a tunnel magnetoresistance structure. In this report, we extend the study to a perpendicular magnetic anisotropic Ta/CoFeB/MgO/CoFeB/Ta junction with ferromagnetic-superparamagnetic pairs and introduce a new type magnetic field sensor . Because the magnetoresistance follows Langevin curve, the present structure, which exhibits a high sensitivity in the low filed region, is easy to be characterized . Moreover, the perpendicular sensor has strong bias-voltage effect, which is tunable by the bias voltage.