Enhancing extraordinary magnetoresistance devices through geometric variations of the outer boundary

Magnetometers with a high sensitivity at weak magnetic fields are desirable for a wide range of sensing applications. Devices that operate on the principle of extraordinary magnetoresistance (EMR) are appealing candidates because of their simplicity and ability to operate at room temperature but they suffer from low sensitivity when compared to state-of-the-art magnetometers such as superconducting quantum interference devices. Since the EMR phenomenon is principally a geometric effect, the shapes of the various parts of the device represent additional degrees-of-freedom which can be manipulated in order to modify the performance of the devices. While previous studies have mostly focused on the inner part of the sensor, in this work, we study the effect of systematically manipulating the shape of the outer boundary. We show that the maximum sensitivity of the device can be increased by 70% by placing a constriction between the voltage or current probes and by 300% if the shape of the boundary is shifted from circular to elliptical. We also show that a finite zero-field sensitivity can be obtained if the horizontal symmetry of the device is broken. These results demonstrate that the outer boundary can have a significant effect on device performance, a finding which paves the way for using shape optimization on the outer boundary for designing sensitive magnetometers.