Electric-field-induced extremely large change in resistance in graphene ferromagnets

Abstract

A colossal magnetoresistance ($\sim 100\times10^3\%$) and an extremely large magnetoresistance ($\sim 1\times10^6\%$) have been previously explored in manganite perovskites and Dirac materials, respectively. However, the requirement of an extremely strong magnetic field (and an extremely low temperature) makes them not applicable for realistic devices. In this work, we propose a device that can generate even larger changes in resistance in a zero-magnetic field and at a high temperature. The device is composed of a graphene under two strips of yttrium iron garnet (YIG), where two gate voltages are applied to cancel the heavy charge doping in the YIG-induced half-metallic ferromagnets. By calculations using the Landauer-B\"{u}ttiker formalism, we demonstrate that, when a proper gate voltage is applied on the free ferromagnet, changes in resistance up to $305\times10^6\%$ ($16\times10^3\%$) can be achieved at the liquid helium (nitrogen) temperature and in a zero magnetic field. We attribute such a remarkable effect to a gate-induced full-polarization reversal in the free ferromagnet, which results in a metal-state to insulator-state transition in the device. We also find that, the proposed effect can be realized in devices using other magnetic insulators such as EuO and EuS. Our work should be helpful for developing a realistic switching device that is energy saving and CMOS-technology compatible.