Role of the electronic structure on the relationship between the crystallinity of CoFe and its tunneling magnetoresistance

Abstract

The influence of the crystallinity of CoFe on tunneling magnetoresistance is investigated in magnetic tunnel junctions with an amorphous Al2 O3 tunnel barrier. An enhancement in the tunneling magnetoresistance is found when the CoFe is made amorphous compared to when it is crystalline. Ab initio electronic structure calculations show substantial differences in the band structures of crystalline and amorphous forms of bulk CoFe alloys but a decreased spin polarization at the Fermi energy in the amorphous phase. We speculate that the increased tunneling magnetoresistance is rather due to changes in bonding at the interface between Al2 O3 and CoFe. © 2009 American Institute of Physics.