Critical Role of W Insertion Layer Sputtering Condition for Reference Layer on Magnetic and Transport Properties of Perpendicular-Anisotropy Magnetic Tunnel Junction

Hiroaki Honjo, Shoji Ikeda, Hideo Sato, Mitsuo Yasuhira, Tetsuo Endoh

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

We investigated an effect of sputtering gas species Ar, Kr, and Xe for deposition of a W insertion layer W(Ar, Kr, and Xe) in the synthetic ferrimagnetic reference layer consisting of [Co/Pt] multilayer/Ru/[Co/Pt] multilayer/W/CoFeB on magnetic properties of the reference layer and tunnel magnetoresistance ratio (TMR ratio) of magnetic tunnel junction (MTJ) stacks with the reference layer. In all the cases, the TMR ratio increased with the increase of the W insertion layer thickness tW and showed a maximum at certain tW. Although the maximum TMR ratio is almost the same for all the cases, tW range in which we observed the maximum TMR ratio is dependent on the gas species; tW = 0.2 nm for Ar, tW = 0.2-0.4 nm for Kr, and tW = 0.2-0.5 nm for Xe, indicating that tW margin giving high-TMR ratio becomes wider with increasing atomic number of the gas species. The lower TMR ratio for W (Ar) at larger tW region is due to the degradation of ferromagnetic coupling between the CoFeB and Co/Pt multilayer sandwiching W, resulting in canting of magnetization in the CoFeB layer. We found that an intermixing of Pt atoms in the Co/Pt multilayer occurred in the MTJ stack with W (Ar), whereas it did not intermix with W (Kr), indicating that the Pt interdiffusion caused the degradation of ferromagnetic coupling through W layer.

Original languageEnglish
Article number8676124
JournalIEEE Transactions on Magnetics
Volume55
Issue number7
DOIs
Publication statusPublished - 2019 Jul

Keywords

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

ASJC Scopus subject areas

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

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