MAGNETIC AND TRANSPORT-PROPERTIES OF NIFE AG AND CO/NIFE/CO/AG MULTILAYERS/

We present a comprehensive study of the structural, magnetic, and tran sport properties of NiFe/Ag multilayers grown by magnetron sputtering onto substrates maintained at liquid-nitrogen temperature. The influen ce of the Ag thickness (t(Ag)), NiFe thickness (t(NiFe)), and number o f bilayers (n) has been studied. These multi layers exhibit antiferrom agnetic and biquadratic coupling for 9 Angstrom<t(Ag)<12.5 Angstrom. F or a given Ag thickness in this interval, the saturation field is inve rsely proportional to t(NiFe) Furthermore, giant magnetoresistance (GM R) is observed with a maximum amplitude for t(NiFe)approximate to 25 A ngstrom. However, the maximum GMR sensitivity Delta R/R/H is obtained at larger NiFe thicknesses. The dependence, of the resistivity and mag netoresistance on the thickness of the NiFe layers has been analyzed w ithin the Camley and Barnas semiclassical theory. The effect of adding thin layers of Co at the NiFe/Ag interfaces has also been investigate d. A doubling of the GMR amplitude at room temperature and a significa nt increase in the saturation field are observed with the introduction of only one atomic plane of Co at each NiFe/Ag interface. A quantitat ive analysis of the data shows that the increase of the GMR is due to a better transmission of the spin-up electrons through the NiFe/Co/Ag interface than through the NiFe/Ag interface. The results are interpre ted in terms of a reinforcement of the magnetic ordering at the NiFe/C o/Ag interfaces, and correlatively a reduction of the interfacial magn etic scattering caused by the presence of the Co layer.