Predictive Materials Design of Magnetic Random-Access Memory Based on Nanoscale Atomic Structure and Element Distribution

Xiang Li*, Taisuke Sasaki, Cecile Grezes, Di Wu, Kin Wong, Chong Bi, Phuong Vu Ong, Farbod Ebrahimi, Guoqiang Yu, Nicholas Kioussis, Weigang Wang, Tadakatsu Ohkubo, Pedram Khalili Amiri, Kang L. Wang

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Magnetic tunnel junctions (MTJs) capable of electrical read and write operations have emerged as a canonical building block for nonvolatile memory and logic. However, the cause of the widespread device properties found experimentally in various MTJ stacks, including tunneling magnetoresistance (TMR), perpendicular magnetic anisotropy (PMA), and voltage-controlled magnetic anisotropy (VCMA), remains elusive. Here, using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy, we found that the MTJ crystallization quality, boron diffusion out of the CoFeB fixed layer, and minimal oxidation of the fixed layer correlate with the TMR. As with the CoFeB free layer, seed layer diffusion into the free layer/MgO interface is negatively correlated with the interfacial PMA, whereas the metal-oxides concentrations in the free layer correlate with the VCMA. Combined with formation enthalpy and thermal diffusion analysis that can explain the evolution of element distribution from MTJ stack designs and annealing temperatures, we further established a predictive materials design framework to guide the complex design space explorations for high-performance MTJs. On the basis of this framework, we demonstrate experimentally high PMA and VCMA values of 1.74 mJ/m2 and 115 fJ/V·m-1 with annealing stability above 400 °C.

Original languageEnglish (US)
Pages (from-to)8621-8629
Number of pages9
JournalNano letters
Volume19
Issue number12
DOIs
StatePublished - Dec 11 2019
Externally publishedYes

Keywords

  • Voltage-controlled magnetic anisotropy
  • crystal structure
  • element distribution
  • magnetic tunnel junction
  • perpendicular magnetic anisotropy
  • tunneling magnetoresistance

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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  • Cite this

    Li, X., Sasaki, T., Grezes, C., Wu, D., Wong, K., Bi, C., Ong, P. V., Ebrahimi, F., Yu, G., Kioussis, N., Wang, W., Ohkubo, T., Khalili Amiri, P., & Wang, K. L. (2019). Predictive Materials Design of Magnetic Random-Access Memory Based on Nanoscale Atomic Structure and Element Distribution. Nano letters, 19(12), 8621-8629. https://doi.org/10.1021/acs.nanolett.9b03190