Tunneling magnetoresistance in GaMnAs/AlAs/GaMnAs ferromagnetic semiconductor heterostructures

We have observed tunneling magnetoresistance (TMR) in epitaxially grown GaMnAs/AlAs/GaMnAs ferromagnetic semiconductor tunnel junctions, The TMR ratio, which is the change in tunnel resistance due to the change of magnetization configuration from parallel to anti-parallel, was more than 70% (maximum 75%) in junctions with a very thin (less than or equal to 1.6 nm) AlAs tunnel barrier, when the magnetic field was applied along the [1 0 0] axis in the film plane. Peculiar TMR characteristics were observed due to the magneto-crystal line anisotropy of GaMnAs, The TMR ratio was found to rapidly decrease with increasing barrier thickness, which is explained by calculations assuming that the parallel wave vector of carriers is conserved in tunneling. (C) 2002 Elsevier Science B.V. All rights reserved.