TEMPERATURE-DEPENDENCE OF THE ELECTRICAL-RESISTIVITY, THERMOPOWER AND MAGNETORESISTANCE OF CO-RE SUPERLATTICES

Detailed measurements of the electrical resistivity (rho, drho/dT), magnetoresistance (DELTA rho/rho) and thermopower (S) have been performed on magnetron-sputtered (Co20angstrom-Re5angstrom)x16 and (Co10 angstrom-Re16 angstrom)x16 superlattices, from 3.7 to 300 K. Resistivity minima were observed at low temperatures due to electron localization/electron-electron interactions, in addition to a magnon resistivity term AT2 e-DELTA/kT, with DELTA approximately 60 K. The magnetoresistance is negative in the two superlattices, both for H parallel-to I and H perpendicular-to I, but DELTA rho/rho is one order of magnitude larger in (Co20 angstrom-Re5 angstrom)x16, where strong antiferromagnetic interlayer coupling exists. In this sample we were able to separate a 'normal' DELTA rho/rho contribution due to spin-orbit/band effects, displaying the usual cos2theta angular dependence. The temperature dependence of the anomalous part of DELTA rho/rho, due to spin-dependent electron scattering, is also studied. The temperature dependence of the transport saturation field (H(s)) has been extracted from such data. The thermopower reveals anomalous small values when compared with pure Co and Co-Cu multilayers. The roles of impurity, magnon and s-d scattering (mediated by phonons) are critically analyzed.