Theoretical and Experimental Investigation of Spintronics-Based Magnetic Sensors for Geophysical Applications in the Nigerian Basement Complex

Background: Magnetic anomaly mapping of Nigeria's Basement Complex for mineral exploration requires highly sensitive magnetic sensors. Spintronics-based sensors, including giant magnetoresistance and tunnelling magnetoresistance devices, offer superior sensitivity compared with conventional fluxgate sensors but have not been optimised for Nigerian geophysical applications. Aim: This study theoretically and experimentally investigated spintronics-based magnetic sensors for geophysical applications in the Nigerian Basement Complex. Methods: Giant magnetoresistance spin valves and magnetic tunnel junction sensors were fabricated by magnetron sputtering and characterised for sensitivity, noise floor, and linearity from DC to 1 kHz. A quantum transport model was developed to describe magnetoresistance behaviour in multilayer structures. Field deployment tests were conducted during magnetic surveys of Basement Complex terrain in Plateau State and Kwara State. Results: The magnetic tunnel junction sensor achieved a sensitivity of 220 mV/mT and a noise floor below 10 pT/Hz0.5 at 1 Hz, surpassing commercial fluxgate sensors by a factor of 6. Magnetic anomaly maps generated using the spintronics sensor resolved features down to 2 nT, enabling identification of previously unmapped mafic intrusions. Conclusion: Spintronics-based sensors provide transformative resolution improvements for Nigerian Basement Complex magnetic surveys. Commercial development of low-cost MTJ sensor arrays for mineral exploration is strongly recommended. Keywords: spintronics, magnetic sensor, geophysics, Nigerian Basement Complex, giant magnetoresistance.