Band structure modification of Al oxide by Ti-alloying and magnetoresistance behavior of magnetic tunnel junctions with Ti-alloyed Al oxide barrier

Song, Jin-Oh; Lee, Seong-Rae; Shin, Hyun-Joon
June 2005
Applied Physics Letters;6/20/2005, Vol. 86 Issue 25, p252501
Academic Journal
We investigated the composition dependence of the band structure of Ti-alloyed Al oxide (TiAlOx), tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junctions (MTJs) with TiAlOx barrier, and the microstructural evolution of Ti–Al alloy films. X-ray absorption spectroscopy indicated that TiAlOx had localized d states in the band gap below the conduction band. As the Ti concentration increased, the resistance×area value and effective barrier height of the MTJs were reduced 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. The TMR ratio increased up to 49% at 5.33 at. % Ti. Ti alloying enhanced the barrier/electrode interface uniformity and reduced microstructural defects. These structural improvements enhanced not only the TMR effect but also the thermal stability of the MTJs.


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