The influence of contact resistance and interface layers in extraordinary magnetoresistance devices

The electrical resistance change of a device when subjected to applied magnetic fields is essential for magnetoresistive magnetometers as well as for studying fundamental transport phenomena in condensed matter. One of the largest magnetoresistances at room temperature is observed in extraordinary magnetoresistance (EMR) devices composed of high-mobility materials with metal inclusions. However, the contact resistance between the constituent materials is often detrimental to their performance. In this work, we study the influence of the interface-near region on the performance of EMR devices using a numerical model, which mimics local doping, carrier depletion, and mobility degradation by independently varying the carrier density and mobility of an interfacial layer. We show that the magnetoresistance decreases by five orders of magnitude when the specific contact resistance increases from 10⁻⁵ to 10⁻² Ω cm². Our results also show that it is beneficial to increase the conductivity of the interface layer, even at the expense of degrading either its carrier density or mobility. This study paves the way for designing contacting strategies for realizing high-performing EMR devices.