Large voltage control of magnetic anisotropy in CoFeB/MgO/OX structures at room temperature

Voltage control of magnetic anisotropy (VCMA) provides an energy-efficient approach to manipulate spintronic devices. Currently, VCMA only shows a weak effect in magnetic tunnel junctions (MTJs) composed of CoFeB/MgO/CoFeB that are the core structure of spintronic memories and logic devices. Multiple approaches have been proposed and studied by researchers to increase the VCMA effect. Here, we demonstrate a large VCMA effect in the CoFeB/MgO/SiO2 double-oxide structure, which can be potentially modified to be compatible with the MTJ cell. The VCMA coefficient as high as 174 fJ/Vm is achieved in this structure at room temperature, with its magnitude comparable to the reported ion-driven VCMA with a high ion-conductive oxide at an elevated temperature. Theoretical analysis indicates that the large VCMA is a magnetoionic effect, which is dominated by ion migration and can be explained by a nanograin cluster model. This double-oxide structure is promising to be extended to an MTJ structure to reduce switching energy in spintronic devices.