Magnetic tunnel sensors with Co-Cu artificial antiferromagnetic (AAF) hardsubsystem

Micron-size magnetic tunnel junctions are studied, in which the pinning of the hard magnetic reference layer is accomplished by the so-called Artifici al Antiferromagnetic Subsystem(AAF). In the AAF, two Co layers are antiferr omagnetically coupled by a 1 nm thick Cu layer, thus giving rise to stabili ty windows larger than 2 kA/m for the AAF, Al2O3-tunnel barriers of 1 and 1 .5 nm Al thickness were put on top of the AAF and at its opposite surface F e detection layers are located. The signal could be enhanced by a factor of two to 22 % by inserting a 1 nm Go-coating between the barrier and the Fe, Thus sensors were realized with signals four times higher than for the GMR counterparts.