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We develop perpendicularly magnetized magnetic tunnel junctions (MTJs) consisting of a CoFeB/Mg40Fe10O50 (MgFeO)/CoFeB multilayer. The use of MgFeO yields a substantial improvement in the flatness of MTJ film stack compared with conventional MTJ films using MgO as a tunnel barrier layer, and 1.7 times enhancement in the perpendicular magnetic anisotropy energy is obtained for the ultrathin CoFeB layer deposited on the MgFeO layer. Nanostructural analysis combined with elemental distribution mapping reveals the formation of highly (001)-oriented MgFeO in the as-deposited MTJ film, and the crystalline MgFeO layer effectively inhibits diffusion of B atoms from the CoFeB layers through the tunnel barrier layer during post-annealing process. Accordingly, the MgFeO-MTJ exhibits superior stability against high temperature annealing and a large tunnel magnetoresistance ratio of 235% is demonstrated in MTJ nanopillar devices after annealing at 400◦C. Ferromagnetic resonance measurements also reveal a reduced magnetic damping in the MgFeO-MTJs owing to the improved uniformity in the CoFeB layer. The present experimental results will facilitate the development of magnetoresistive memory devices with increasing memory density and higher energy efficiencies.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: transmission electron microscopy

Date published: 2024-02-09

Publisher: Elsevier BV

Journal:

• Acta Materialia (ISSN: 13596454) vol. 267 119749

Funding:

• New Energy and Industrial Technology Development Organization JPNP16007

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5406

First published URL: https://doi.org/10.1016/j.actamat.2024.119749

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Updated at: 2026-02-09 12:30:04 +0900

Published on MDR: 2026-02-09 09:54:03 +0900