Influence of a magnetic seed line on the switching behaviour of submicrometre sized magnetic tunnel junctions

Magnetic tunnel junctions in the sub-micrometre range have been patterned b y electron beam lithography. The hard reference electrode is composed of an artificial antiferromagnetic subsystem while the soft magnetic detection l ayer is Permalloy (NiFe). The magnetic switching characteristic is studied for various seed layers. For a polycrystalline iron seed line the magnetore sistance switching curve is irregular and not well behaved, while for a non magnetic seed layer (Ru) the reproducibility is good and the switching can be related to the shape of the element. We discuss possible coupling mechan isms and show that the magnetization reversal of the soft layer is mainly d riven by the large stray fields of moving Neel-type domain walls in the Fe seed layer.