Magnetic Field-Free Giant Magnetoresistance in a Proximity- and Gate-Induced Graphene Spin Valve

Abstract

Due to its two dimensional nature, ferromagnetism and charge doping can be induced by proximity and electric field effects in graphene. Taking advantage of these features, we propose an electrically engineered spin valve by combining two magnetic insulators (using EuO, EuS, or YIG) and three coating gates. Two top gates are used to cancel the heavy electron doping's in these magnets and one back gate is used to utilize the normal or half-metallic ferromagnetisms. We demonstrate that, when the second top gate is tuned to utilize the insulating or spin insulating states, huge giant magnetoresistance (GMR) at high temperature (several times of $10^5\%$ at 68K and 100K) can be achieved for EuO and YIG. These results imply a distinguished GMR that is magnetism tunable, vertical configured (ferromagnetism versus insulating), and magnetic field-free. Our work may offer a viable path to a tantalizing magnetic field-free spintronics.