Enhanced magnetoresistance in annealed and Cr doped Fe/Cr multilayers

Abstract

In previous work we reported that the magnetoresistance of Fe/Cr multilayers can be increased by annealing the films at moderate temperatures, which increases the spin-dependent scattering of the conduction electrons. Here we present Mössbauer data that demonstrate that the structural effect of annealing is to promote Cr interdiffusion into the bulk of the iron layers rather than short scale intermixing at the interfaces. We have also investigated the effect of increasing the asymmetric scattering by adding chromium to the iron in Fe/Cr multilayers. The additional Cr was either alloyed with the Fe in compositions ranging from 1.5% to 50% Cr in Fe, or concentrated into 1 or 2 Å layers embedded at various positions in the Fe. We report enhanced room-temperature magnetoresistance of up to 11.4% in sputter-deposited Fe/Cr multilayers when the Fe layers are doped with 20% Cr. The maximum magnetoresistance observed for samples with embedded Cr layers was 10.5%. In comparison, the magnetoresistance was 7.5% in a similar, undoped sample.