Dependence on annealing temperatures of tunneling spectra in high-resistance CoFeB/MgO/CoFeB magnetic tunnel junctions

Rie Matsumoto, Shingo Nishioka, Masaki Mizuguchi, Masashi Shiraishi, Hiroki Maehara, Koji Tsunekawa, David D. Djayaprawira, Naoki Watanabe, Yuichi Otani, Taro Nagahama, Akio Fukushima, Hitoshi Kubota, Shinji Yuasa, Yoshishige Suzuki

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

We investigated the annealing temperature dependence of differential tunneling conductance spectra (d I / d V as a function of V) in CoFeB/textured MgO(001)/CoFeB magnetic tunnel junctions (MTJs) that exhibit the giant tunneling magnetoresistance (TMR) effect at room temperature. The spectra were strongly affected by annealing the MTJs. A reduction in d I / d V at around ±300 mV was observed only in annealed MTJs in which the CoFeB electrodes were crystallized in a bcc(001) structure. Because the reduction in conductance was observed in both MTJs that have a 1.8-nm-thick MgO barrier and MTJs that have a 3.2-nm-thick MgO barrier, we concluded that Δ5 and Δ2′ evanescent states, which rapidly decay in the MgO tunneling barrier, are not the cause of the reduction in conductance. We believe the cause of the reduction is either the electronic structure of the interfaces between MgO(001)/bcc CoFeB(001) after annealing or a particular feature of Δ1 states in MgO(001) or bcc CoFeB(001).

Original languageEnglish
Pages (from-to)574-578
Number of pages5
JournalSolid State Communications
Volume143
Issue number11-12
DOIs
Publication statusPublished - 2007 Sep 1
Externally publishedYes

Keywords

  • A. Magnetic films and multilayers
  • D. Electronic band structure
  • D. Electronic transport
  • D. Tunneling

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry

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