  Magnetic random access memory schemes employing magnetoelectric coupling to
write binary information promise outstanding energy efficiency. We propose and
demonstrate a purely antiferromagnetic magnetoelectric random access memory
(AF-MERAM) that offers a remarkable 50 fold reduction of the writing threshold
compared to ferromagnet-based counterparts, is robust against magnetic
disturbances and exhibits no ferromagnetic hysteresis losses. Using the
magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal
switching via gate voltage pulses and all-electric readout at room temperature.
As no ferromagnetic component is present in the system, the writing magnetic
field does not need to be pulsed for readout, allowing permanent magnets to be
used. Based on our prototypes of these novel systems, we construct a
comprehensive model of the magnetoelectric selection mechanism in thin films of
magnetoelectric antiferromagnets. We identify that growth induced effects lead
to emergent ferrimagnetism, which is detrimental to the robustness of the
storage. After pinpointing lattice misfit as the likely origin, we provide
routes to enhance or mitigate this emergent ferrimagnetism as desired. Beyond
memory applications, the AF-MERAM concept introduces a general all-electric
interface for antiferromagnets and should find wide applicability in purely
antiferromagnetic spintronics devices.
