Magnetic Tunnel Junctions With [Co/Pd]-Based Reference Layer and CoFeB Sensing Layer for Magnetic Sensor

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We investigated the tunneling magnetoresistance (TMR) properties for the magnetic sensor application in MgO-based magnetic tunnel junctions (MTJs) using a perpendicularly magnetized [Co/Pd]-based reference layer and an in-plane magnetized CoFeB sensing layer with various thicknesses (tCoFeB). Linear TMR curves to an out-of-plane magnetic field were successfully obtained with a dynamic range of more than 600 Oe, corresponding to the coercivity of the [Co/Pd]-based reference layer. The MTJs showed the highest sensitivity of 0.026%/Oe for tCoFeB = 1.8 nm and the smallest nonlinearity of 0.11% full scale for tCoFeB= 3 nm. We clarified that the sensitivity and the nonlinearity in the MTJs are significantly associated with tCoFeB, which is attributed to the change in the anisotropy field of the CoFeB sensing layer.