From direct to inverse GMR: introduction of Cr in Fe/Cu superlattices

It is well known that layered systems can present giant magnetoresistance ( GMR). Particularly, the multilayers Fe-N/Cu-8/Fe-M/Cr/Fe-M/Cu-8 show invers e GMR. That is, the electrical conductivity decreases with the applied magn etic field. In the most common multilayers the conductivity increases with the applied field and this kind of GMR is called direct. In general the GMR is attributed to spin-dependent scattering in the bulk and mainly at inter faces. In this work we calculate the electronic band contribution to the GM R for Fe-3/Cu-4/Fe/Cr/Fe/Cu-4 and Fe-3/Cu-4 multilayers within the semiclas sical approximation. The electrical conductivity is obtained in the ballist ic and diffusive regimes. The results show a large change in the GMR behavi or when one layer of Cr is introduced within the Fe layers. The GMR calcula ted in the CPP configuration (current flowing perpendicular to layers) of F e-3/Cu-4 is of the direct type, with a value of about 40% while that obtain ed for Fe-3/Cu-4/Fe/Cr/Fe/Cu-4 is inverse and of the order of 45%. In the C IP configuration (current flowing parallel to the layers) the calculated GM R is direct with a value of about 35% for the system without Cr while, by t he introduction of Cr, we obtain also a direct GMR but of about 3%. (C) 200 1 Published by Elsevier Science B.V.