Influence of thickness and band structure of insulating barriers on resistance and tunneling magnetoresistance properties of magnetic tunnel junctions with Al-oxide and Ti-alloyed Al-oxide barriers

Jin Oh Song, Seong Rae Lee, Hyun Joon Shin

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We investigated the influence of insulating barrier thickness and the Ti composition dependence of the band structure of Al-oxide on the resistance and tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junction (MTJ). Low resistance × area (RA) value (1.1 MΩ μm2) was achieved by decreasing the Al-oxide thickness down to 1.0 nm. However, this led to the partial oxidation of the bottom ferromagnetic (FM) electrode of the junction and non-continuous thin barriers by the occurrence of pinholes, with low TMR ratio of 8.3%. For an alternative for low RA value, we developed a new Ti-alloyed Al-oxide (TiAlOx) that had lower band gap than Al-oxide as an insulating barrier of MTJ. As the Ti concentration increased up to 5.33 at.% Ti in Al, the RA value of the MTJs was reduced from 9.5 to 0.69 MΩ μm2, owing to the band-gap reduction of TiAlOx caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlOx has localized d states in the band gap below the conduction band. In addition, the TMR ratio increased with the Ti concentration and reached a maximum of 49% at 5.33 at.% Ti owing to the microstructural evolution of Ti-Al alloy film in the pre-oxidation state.

Original languageEnglish
Pages (from-to)18-20
Number of pages3
JournalCurrent Applied Physics
Volume7
Issue number1
DOIs
Publication statusPublished - 2007 Jan

Keywords

  • Barrier thickness
  • Low resistance MTJ
  • Magnetic tunnel junction
  • TiAlO barrier

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy(all)

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