The Limit of the Giant Magnetoresistance Effect in Only Three Layers

Abstract

The giant magnetoresistance (GMR) behavior of the very simplest structures consisting of one nonmagnetic layer sandwiched in between two ferromagnetic layers has been thoroughly investigated. It has been shown that these trilayers exhibit room temperature GMR effect amplitudes of 16% that match the GMR values of well designed biased spin-valve structures. The oscillatory interlayer exchange coupling (IEC) has been determined for different series of structures like glass/{Py(= Ni 80 Fe 20 )/FM}/spacer/FM, with FM = Co or Ni 57 Co 43 and the spacer materials such as Cu or Cu 85 Ag 10 Au 5 , over a wide range of spacer layer thickness. The GMR effect amplitude has also been extracted as a function of the individual layer thickness. It has been demonstrated, that an extended Stoner-Wohlfarth model can very well be used to predict the GMR characteristics of these trilayers or more complicated structures. The sensitivity of these structures can be as high as 40%/mT. GMR effects of up to 20% at room temperature have been realized with dual structures of type glass/(Py/Co}/Cu/Co/Cu/Co. Changing the thickness of the middle Co layer the GMR effect amplitude as well as the saturation field can be tailored. In addition it has been shown, that the Cu 85 Ag 10 Au 5 spacer material is much more stable to temperature exposure than pure Cu.