Thickness dependence of giant magnetoresistance of AgNiFe heterogeneous alloys films

We have investigated the thickness dependence of the giant magnetoresistance (GMR) observed in AgNiFe heterogeneous alloy films. The films were sputtered from a mosaic target at the system ambient temperature onto glass substrates. In order to maintain interfacial uniformity, and to control the spin-dependent transmission of electrons at the AgNiFe film interfaces, they were covered by 200-Angstrom-thick NiFe under- and overlayers. The samples have total thicknesses in the range 400-3000 Angstrom. The film resistivity, magnetoresistivity, and magnetization were measured in the temperature range 4-300 K and in fields of up to 1.1 T and the structure examined using both large- and small-angle x-ray diffraction. The results indicate that the observed thickness dependence of the GMR of the AgNiFe films is within the experimental error It is postulated that this is due to coherent spin transmission of conduction electrons across the sandwich interfaces which does not degrade the GMR by mixing of the spin currents. (C) 1996 American Institute of Physics.