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

We demonstrated the noise performances of Al
₂
O
₃
-based magnetic tunnel junction sensors (MTJs) in the low-frequency regimes. Conetic alloy Ni
₇₇
Fe
₁₄
Cu
₅
Mo
₄
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.