Electric-Field-Controlled Magnetoelectric RAM: Progress, Challenges, and Scaling

Abstract

We review the recent progress in the development of magnetoelectric random access memory (MeRAM), based on electric-fieldcontrolled writing in magnetic tunnel junctions (MTJs). MeRAM uses the tunneling magnetoresistance (TMR) effect for readout in a two-terminal memory element, similar to other types of magnetic random access memory (MRAM). However, the writing of information is performed by voltage control of the magnetic anisotropy (VCMA) at the interface of an MgO tunnel barrier and the CoFeB-based free layer, as opposed to current-controlled (e.g. spin-transfer torque, STT or spin-orbit torque, SOT) mechanisms. We present results on voltage-induced switching of MTJs in both resonant (precessional) and thermally activated regimes, which demonstrate fast (< 1 ns) and ultralow-power (< 40 fJ/bit) write operation at voltages ~ 1.5 -2 V. We also discuss the implications of the VCMA-based write mechanism on memory array design, highlighting the possibility of crossbar implementation for high bit density. Results are presented from a 1 Kb MeRAM test array. Endurance and voltage scaling data are presented. The scaling behavior is analyzed, and material-level requirements are discussed for the translation of MeRAM into mainstream memory applications.Index Terms-Nonvolatile memory, MeRAM, MRAM, voltage control of magnetic anisotropy, spin transfer torque. † These authors contributed equally to this work.

Highly efficient voltage control of spin and enhanced interfacial perpendicular magnetic anisotropy in iridium-doped Fe/MgO magnetic tunnel junctions

“…These results indicate the feasibility of constructing voltage-driven spintronic devices, such as voltage-torque magnetoresistive random access memory devices. 20 The VCMA effect is observed at the interface between an ultrathin ferromagnetic metal and dielectric layers. This effect can be induced by purely electronic effects and by chemical or mechanical effects.…”

Voltage control of magnetic anisotropy in epitaxial Ru/Co2FeAl/MgO heterostructures

“…Achieving a sufficient voltage control of magnetic anisotropy (VCMA) in magnetic heterostructures is of particular importance for realizing energy-efficiency electronic devices with ultralow power consumption, such as voltage-torque magnetoresistive random access memories (MRAMs)12 and low power logic LSIs34. By using voltage-controlled magnetization switching, the power consumption for manipulating a bit cell is proposed to be ~1 fJ, which is two orders of magnitude lower than ~0.1 pJ in the spin transfer torque (STT) technology5.…”

Nanostructure‐enhanced magnetoelectric/magnetostrictive properties and reduced losses in self‐assembled epitaxial CuFe2O4–BiFeO3 layers on Pb(Mg1/3Nb2/3)O3–33at%PbTiO3 crystals

“…Because of coexisting polarization and magnetization orders, multiferroic materials have been studied for various applications. [1][2][3][4][5] These include electric-field-controlled magnetoelectric (ME) random access (MeRAMs) 2 memories, logic devices, 6 and even solid-state synapse-like neuromorphic learning. 7 Magnetoelectric materials offer several potential advantages, such as electric field (E) control, 4,5 high speed, 2 and the possibility of nonvolatility.…”

“…[1][2][3][4][5] These include electric-field-controlled magnetoelectric (ME) random access (MeRAMs) 2 memories, logic devices, 6 and even solid-state synapse-like neuromorphic learning. 7 Magnetoelectric materials offer several potential advantages, such as electric field (E) control, 4,5 high speed, 2 and the possibility of nonvolatility. [8][9][10] The mechanical quality factor (Q) is often used as a measure of energy loss per cycle 11,12 and/or the efficiency 13,14 : higher Q generally implies higher efficiencies and lower losses.…”