Comparison of Sensitivity and Low-Frequency Noise Contributions in Giant-Magnetoresistive and Tunneling-Magnetoresistive Spin-Valve Sensors with a Vortex-State Free Layer

For giant- (GMR) and tunneling- (TMR) magnetoresistive sensors, noise and sensitivity are crucial in determining the smallest magnetic field that can be detected. Both parameters are analyzed for a sensor design comprising a circular free layer that features a flux-closed vortex magnetization state. The authors find that in the low-frequency regime, where noise is predominantly pink, the detectivity depends $o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y$ on the active sensor area, not on the magnetoresistance ratio or bias voltage, and is the same for both GMR and TMR devices. As such sensors are widely used in $e.g.$ biomedical, automotive, and aerospace applications, this insight is expected to be far-reaching.