Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

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 AF-MERAM elements, 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. In particular, the read out of the magnetic state is realized by Zero-Offset Hall [Kosub et al., Phys. Rev. Lett. 115, 097201 (2015)] which can detect the proximity magnetization that developes in metallic electrodes at the boundary of insulating antiferromagnets. This technique possesses considerable applicability to the field of antiferromagnetic spintronics, as it can probe the net magnetization of both metallic and insulating antiferromagnetic thin films.