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

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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 μm 2) 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 (TiAlO x) 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 μm 2, owing to the band-gap reduction of TiAlO x caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlO x 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 1

Fingerprint

Tunnelling magnetoresistance
Tunnel junctions
tunnel junctions
Band structure
Oxides
oxides
Energy gap
low resistance
Oxidation
oxidation
Microstructural evolution
pinholes
Conduction bands
conduction bands
occurrences
orbitals
Electrodes
electrodes
Chemical analysis

Keywords

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

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science (miscellaneous)

Cite this

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title = "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",
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 μm 2) 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 (TiAlO x) 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 μm 2, owing to the band-gap reduction of TiAlO x caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlO x 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.",
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author = "Song, {Jin Oh} and Lee, {Seong Rae} and Shin, {Hyun Joon}",
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T1 - 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

AU - Song, Jin Oh

AU - Lee, Seong Rae

AU - Shin, Hyun Joon

PY - 2007/1/1

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N2 - 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 μm 2) 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 (TiAlO x) 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 μm 2, owing to the band-gap reduction of TiAlO x caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlO x 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.

AB - 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 μm 2) 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 (TiAlO x) 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 μm 2, owing to the band-gap reduction of TiAlO x caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlO x 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.

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