Strain and Exchange Bias-Enabled Field-Free Voltage-Controlled Magnetic Anisotropy Switching

Abstract

In pursuing energy-efficient and high-performance nonvolatile magnetic memory devices, this study explores voltage-induced techniques, specifically voltage-controlled magnetic anisotropy (VCMA), as an alternative to current-induced methods, which suffer from Ohmic loss. The perpendicular magnetic anisotropy (PMA) nanomagnet, known for its superior stability and scalability compared to in-plane variants, VCMA switching in PMA system requires an in-plane symmetry breaking field, which limits its practicality for on-chip applications. We investigate field-free VCMA switching utilizing strain from a piezoelectric layer and an exchange bias from an antiferromagnetic material. Using macro-spin simulations based on the Landau-Lifshitz-Gilbert equation, we systematically analyze how the VCMA effect, strain-induced magnetoelastic effect, exchange bias, oxide and free layer thicknesses, and damping constant affect the switching performance of the device. The write error rate (WER) drops drastically from 0.2 (without stress) to \({10}^{-6}\) (100 MPa stress), showcasing the effectiveness of our approach. We also find that the damping constant, especially in the 0.01–0.05 range, plays a crucial role in further optimizing the switching performance of the device. This study offers new insights for enhancing magnetic memory technology.