Angular Dependence of Low-Frequency Noise in Al $_{2}$ O $_{3}$ -Based Magnetic Tunnel Junction Sensors

We demonstrated the noise performances of Al₂O₃-based magnetic tunnel junction sensors (MTJs) in the low-frequency regimes. Conetic alloy Ni₇₇Fe₁₄Cu₅Mo₄ was deposited as both the MTJ pinned layer and free layer because of its superb magnetically soft properties. A rotating magnetic field was employed to investigate the angular dependence of the MTJ low-frequency noise. Hooge parameter was applied for parameterizing the low-frequency noise. The measurement results demonstrate that the Hooge parameters are angular-dependent and they exhibit a linear relation with respect to the angular magnetoresistive susceptibility. It can be also observed that the Hooge parameters possess a higher value when the Conetic MTJs are in the region of antiparallel state. These results indicate that the magnetic fluctuations in the ferromagnetic layers contribute to the low-frequency noise level in Conetic MTJ sensors.