Direct observation of the perpendicular shape anisotropy and thermal stability of p-STT-MRAM nano-pillars

Almeida, T. , Lequeux, S., Palomino, A., Sousa, R., Fruchart, O., Prejbeanu, I. L., Dieny, B., Masseboeuf, A. and Cooper, D. (2022) Direct observation of the perpendicular shape anisotropy and thermal stability of p-STT-MRAM nano-pillars. arXiv, (Unpublished)

Abstract

Perpendicular shape anisotropy (PSA) offers a practical solution to downscale spin-transfer torque Magnetic Random-Access Memory (STT-MRAM) beyond the sub-20 nm technology node whilst retaining thermal stability of the storage layer magnetization. However, our understanding of the thermomagnetic behavior of PSA-STT-MRAM is often indirect, relying on magnetoresistance measurements and micromagnetic modelling. Here, the magnetism of a FeCoB / NiFe PSA-STT-MRAM nano-pillar is investigated using off-axis electron holography, providing spatially resolved magnetic information as a function of temperature, which has been previously inaccessible. Magnetic induction maps reveal the micromagnetic configuration of the NiFe storage layer (60 nm high, 20 nm diameter), confirming the PSA induced by its 3:1 aspect ratio. In-situ heating demonstrates that the PSA of the FeCoB / NiFe composite storage layer is maintained up to at least 250 degrees centigrade, and direct quantitative measurements reveal the very moderate decrease of magnetic induction with temperature. Hence, this study shows explicitly that PSA provides significant stability in STT-MRAM applications that require reliable performance over a range of operating temperatures.

• Item Type: Articles
• Additional Information: CEA-Leti is a Carnot Institute. This work was supported by the French ANR via Carnot funding and the European Research Council (ERC MAGICAL, 664209).
• Status: Unpublished
• Refereed: No
• Glasgow Author(s) Enlighten ID: Almeida, Dr Trevor
• Authors: Almeida, T., Lequeux, S., Palomino, A., Sousa, R., Fruchart, O., Prejbeanu, I. L., Dieny, B., Masseboeuf, A., and Cooper, D.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: arXiv
• Copyright Holders: Copyright © 2022 The Authors
• Publisher Policy: Reproduced under a Creative Commons License