Offset Field Control for VCMA-MRAM

Abstract

One of the key challenges in the industrialisation of Voltage Controlled Magnetic Anisotropy-Magnetic Random Access Memory (VCMA-MRAM) is the reliability of the writingprocess. As VCMA is a non-deterministic write process, it is more sensitive to any offset of the Free Layer (FL) (mu H-0(off)) due to stray fields generated by the Hard Layer (HL)/Reference Layer(RL), as compared to alternative MRAM technologies. In this work,a simple method for the control of mu H-0(off) is demonstrated. Therelative moments of the HL and RL can be tuned by varying the Coconcentration, and number of repeats, in a typical Co/Pt HL. The effect of this is demonstrated at thin film and device level where a FL offset of mu H-0(off) =0mT is obtained, with minimal change in any other device properties. Furthermore, the switching probabilitydistribution, with respect to VCMA pulse width, is shown to besymmetric in the optimised device. This result shows that with simple tuning, one of the key challenges to VCMA-MRAM can be solved.