Influence of the interlayer exchange coupling on the electric transport in Fe/Cr/Fe and Fe/Cr/T/Fe (T=Mn, V): An ab initio study

The electronic and magnetic properties of the Fe/Cr/Fe systems are studied within the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method by performing calculations for varying spacer thickness. The obtained interlayer exchange coupling shows a 2 ML period as well as phase slips due to the spin-density wave (SDW). In agreement with experimental findings we are able to prove that Mn impurities destroy the spin-density wave, whereby a statistically disordered Cr-Mn alloy spacer exhibits substantially larger effects than an atomic Mn layer separating the Cr spacer from the Fe leads. Using for such a layer V instead of Mn the SDW survives, but leads to a phase shift. The 2 ML period remains if an in-between layer of Mn or V is considered, whereas in the case of alloy formation in the spacer a superposition of different periods occurs. Further effort has been devoted to investigate the transport properties of the Fe/Cr/Fe sandwiches in the current perpendicular to the plane geometry in order to examine possible differences in the giant magnetoresistance due to the above-mentioned changes in the interlayer exchange coupling. From the present investigations we are able to show that the changes in the magnetic coupling, e.g., periods of oscillations or shifts, can directly be observed in the giant magnetoresistance.