Voltage-Driven Magnetization Switching Using Inverse-Bias Schemes

We study the influence of inverse biases applied before and after a write pulse on the write-error rate (WER) of voltage-driven magnetization switching in magnetic tunnel junctions. It is demonstrated that the inverse bias applied after the write pulse is effective not only for improving the minimum value of the WER but also for broadening the operating pulse-width window. In contrast, an inverse bias applied before the write pulse hardly improves the WER or even narrows the operating window. Numerical simulations based on the macrospin approximation reproduce these experimental results well and a detailed analysis of the magnetization trajectory reveals that the observed write-error increase is due to a change in the magnetization angle before writing. These experimental results, as well as the numerical analysis, should facilitate the development of writing schemes in voltage-driven magnetic random-access memories.