A New Mechanism for Electric-field Controlled Bidirectional Magnetization Switching
Switching of perpendicular magnetic tunnel junctions (p-MTJs) with only an electric-field (E-field) has been the holy grail for realizing ultra-low energy memory and computing devices. Most efforts have been focused on manipulating the magnetic anisotropy in interfacial perpendicular magnetic anisotropy (i-PMA) materials. The need of another driving force, e.g. external magnetic field, is an obstacle for this approach. Bidirectional parallel-antiparallel magnetization switching in p-MTJs with only an E-field has not yet been reported. We report a novel switching mechanism to realize a parallel-antiparallel magnetization switching between the free and reference layers of p-MTJs by only E-field. Here the voltage-controlled magnetic anisotropy (VCMA) effect is combined with E-field mediated exchange coupling in a synthetic antiferromagnet (SAF) which favors ferromagnetic (FM) or antiferromagnetic (AFM) orientation. We demonstrate such switching in p-MTJs with a unique SAF free layer. Bidirectional switching and voltage-controlled random telegraphic switching were observed at room temperature in the sub-100 nanometer L10-FePd SAF p-MTJs at a critical current density ~1x10(5) A/cm2. This simple and efficient design may eliminate the main obstacle to the development of ultra-low energy nonvolatile memory and logic devices as well as provide an attractive pathway towards stochastic and neuromorphic computing.