The role of spin-dependent impurity scattering in Fe/Cr giant magnetoresistance multilayers

To probe the mechanism of giant magnetoresistance (GMR) observed in Fe/Cr multilayers, we have sputter deposited at the interfaces of Fe(15 Å)/Cr(12 Å) multilayers an additional, ultrathin (0-4 Å) layer of a variety of third elements (V, Mn, Ge, Ir, and Al). When alloyed with Fe in dilute concentrations, the elements chosen have known resistivities for spin-up (ρ↑) and spin-down (ρ↓) currents arising from spin-dependent impurity scattering. The results show a clear correlation between α=ρ↓/ρ↑ of the respective element and the way in which GMR varies with the ultrathin layer thickness. In addition, little difference in GMR is observed between multilayers where the ultrathin layer thickness t/2 is deposited on every Fe/Cr interface and those with a thickness t deposited on alternate interfaces. This investigation demonstrates the importance of the type and total number of scattering centers per multilayer period to the GMR effect.