Structural dependence of the tunnel magnetoresistance for magnetic tunnel junctions with a full-Heusler Co2Fe(Al,Si) electrode

Abstract

We have investigated the crystal structure and magnetic moment of the Co2FeAl and Co2FeSi films deposited onto thermally oxidized Si and MgO(100) single-crystal substrates, and the structural effect on the tunnel magnetoresistance (TMR) of the magnetic tunnel junctions (MTJs) using a Co2FeZ (Z=Al or Si). The structure was changed by the substrate and postannealing temperatures, in which the fully epitaxial and polycrystalline Co2FeAl and Co2FeSi films were obtained with the different disorder structure. The magnetic moment of Co2FeAl films was found to be uninfluenced by the crystal structure. Spin-valve-type MTJs consisting of Co2FeZ(100nm)∕Al(1.2nm)-oxide∕Co75Fe25(2nm)∕IrMn(10nm)∕Ta(60nm) were fabricated (Z=Al or Si) on thermally oxidized Si and MgO(100) single-crystal substrates. The maximum TMR obtained is about 50% at room temperature for MTJs with Co2FeAl films, regardless of the crystal structure of Co2FeAl.