INTERFACIAL POLARIZATION EFFECT ON THE INTERLAYER COUPLINGS IN CO RH SANDWICHES/

The structural, magnetic and transport properties of Co/Rh sandwiches grown by ultra high vacuum evaporation and sputtering have been studie d. High-energy electron diffraction observations during the growth rev eal that both Co and Rh layers have been stabilised in the (111) fee s tructure for the evaporated sandwiches. X-ray measurements performed o n sputtered samples show a predominant fee polycrystalline structure o f the stacks with a preferential (111) texture. Magnetisation and magn etoresistance measurements show a very strong antiferromagnetic exchan ge coupling for thin Rh layers, reaching 39 erg/cm(2) for 4.8 Angstrom Rh, the strongest ever observed in exchange coupled systems. This val ue is in good agreement with the value of 38 erg/cm(2) obtained by ab initio calculations for Co/Rh (hcp) superlattices. This is explained b y the magnetic nature of the Co/Rh interfaces. Indeed, the variation o f the measured saturation magnetisation as a function of the Co layer thickness shows no evidence of Co moment reduction for the Co atoms lo cated at the interfaces, even for the very thin layers. The value of t he preserved magnetic moments of the cobalt atoms at the interfaces is confirmed by ab initio calculations for Co/Rh superlattices taking th e intermixing into account.