Extraordinary magnetometry: A review on extraordinary magnetoresistance

Extraordinary magnetoresistance (EMR) is a geometric magnetoresistance effect occurring in hybrid devices consisting of a high-mobility material interfaced with a high-conductivity material. The change in resistance can exceed 10⁷% at room temperature when a strong magnetic field is applied. Magnetic field sensors based on EMR hold the potential for measuring weak magnetic fields with an unprecedented sensitivity, yet, to date this potential is largely unmet. In this work, we provide an extensive review of the current state-of-the-art in EMR devices with a focus on the geometry of the hybrid devices, the constituent material properties, and applications of EMR. We present a direct comparison of the best devices in literature across magnetoresistance, sensitivity and noise equivalent field for different materials and geometric designs. The compilation of studies collected in this review illustrates the extremely rich possibilities for tuning the magnetoresistive behaviour by varying the device geometry and material properties. In addition, we aim to improve the understanding of the effect and the interplay between the geometry and material properties. Finally, we discuss recent trends in the field and future perspectives for EMR.