Exchange-biased magnetic tunnel junctions: Dependence of offset field on junction width

Abstract

Exchange biased magnetic tunnel junctions were prepared by dc-magnetron sputtering in an ultrahigh vacuum (UHV) sputtering system and patterned by optical lithography. The magnetic switching characteristics of the magnetic tunnel junction structures vary systematically with the size and shape of the junction. The magnetic hysteresis loop of the free ferromagnetic layer, as measured resistively, is offset from zero magnetic field by a small offset field. The offset field has two components, a weak positive ferromagnetic coupling field and a negative magnetostatic coupling field. The offset field is in good agreement with the magnitude of the demagnetization field predicted from the moment of the pinned ferromagnetic layer.