Universal material trends in extraordinary magnetoresistive devices

Abstract

Extraordinary magnetoresistance (EMR) is a geometric magnetoresistance emerging in hybrid systems typically comprising a high-mobility material and a metal. Due to a field-dependent redistribution of electrical currents in these devices, the electrical resistance at room temperature can increase by 10^7% when applying a magnetic field of 5 T. Although EMR holds considerable potential for realizing sensitive, all-electronic magnetometers, this potential is largely unmet. A key challenge is that the performance of EMR devices depends very sensitively on variations in a vast parameter space where changes in the device geometry and material properties produce widely different EMR performances. The challenge of navigating in the large parameter space is further amplified by the poor understanding of the interplay between the device geometry and material properties. By systematically varying the material parameters in four key EMR geometries using diffusive transport simulations, we here elucidate this interplay with the aim of finding universal guidelines for designing EMR devices. Common to all geometries, we find that the sensitivity scales inversely with the carrier density, while the MR reaches saturation at low carrier densities. Increasing the mobility beyond 20,000 cm^2/Vs is required to observe strong EMR effects at 1 T with the optimal magnetoresistance observed for mobilities between 100,000-500,000 cm^2/Vs. An interface resistance below 10^-4 Ohm*cm^2 between the constituent materials in the hybrid devices was also found to be a prerequisite for very high magnetoresistances in all geometries. By further simulating several high-mobility materials at room and cryogenic temperatures, we conclude that encapsulated graphene and InSb are amongst the most promising candidates for EMR devices showing high magnetoresistance exceeding 10^7% below 1 T at room temperature. This study paves the way for understanding how to realize EMR devices with record-high magnetoresistance and high sensitivity for detecting magnetic fields.