Impact of Tungsten Sputtering Condition on Magnetic and Transport Properties of Double-MgO Magnetic Tunneling Junction with CoFeB/W/CoFeB Free Layer

H. Honjo, S. Ikeda, H. Sato, K. Nishioka, T. Watanabe, S. Miura, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, H. Koike, H. Inoue, M. Muraguchi, M. Niwa, H. Ohno, T. Endoh

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

We investigated an effect of sputtering gas species (Ar, Kr, and Xe) for deposition of a W insertion layer in the CoFeB/W/CoFeB free layer on magnetic properties of the free layer and tunnel magnetoresistance (TMR) ratio of magnetic tunnel junctions (MTJs) stacks using the free layer annealed at 400 °C for 1 h. As the W insertion layer thickness tW increased, we found the degradation of perpendicular anisotropy and larger reduction of saturation magnetic moment per unit area mS in the free layer using Ar compared to those using Kr and Xe. We also found a smaller TMR ratio for the MTJ stack using Ar compared to those using Kr and Xe. Energy-dispersive X-ray spectrometry line analysis revealed more significant interdiffusion between W and CoFeB layers in the free layer using Ar than those using Kr and Xe, that could result in the smaller m and perpendicular anisotropy in the free layer and smaller TMR ratio for the MTJ stack using Ar than those using Kr and Xe. We also investigated concentration of Ar, Kr, and Xe in W layers deposited using Ar, Kr, and Xe, respectively, by high-resolution Rutherford backscattering spectrometry, revealing that 0.2 at% Ar was detected in the W layer using Ar, while Kr and Xe were not detected in W layers using Kr and Xe. Such a difference in concentration of inert gas atoms in the W layer could be one possible reason for the difference about degree of interdiffusion between W and CoFeB layers.

Original languageEnglish
Article number7920343
JournalIEEE Transactions on Magnetics
Volume53
Issue number11
DOIs
Publication statusPublished - 2017 Nov

Keywords

  • CoFeB-MgO
  • double interfaces structure
  • interfacial anisotropy
  • magnetic tunnel junction (MTJ)
  • perpendicular anisotropy
  • spin-transfer-torque magnetoresistive random access memory (STT-MRAM)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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