MgO Based Magnetic Tunnel Junctions With Co$_{20}$Fe$_{60}$B$_{20}$ Sensing Layer for Magnetic Field Sensors

We applied Co₂₀Fe₆₀B₂₀ layers with thicknesses from 1.2 to 1.5 nm to the sensing layers of MgO based magnetic tunnel junctions (MTJs) with spin-valve-type structures annealed at 350 °C for magnetic field sensors. The CoFeB layer on MgO had in-plane magnetic anisotropy and also slight perpendicular magnetic anisotropy that originated at the MgO/CoFeB interface. MR characteristics of high reversibility and linearity were confirmed at a CoFeB thickness of 1.3 nm. We consider that the hysteresis-free properties of the sensing layer were obtained by the balance between in-plane magnetization and other components in magnetization including out-of-plane magnetization.