Effect of sputtering pressure on the structure and current-perpendicular-to-the-plane magnetotransport of Co/Ag multilayered films

Co/Ag multilayers have been sputter-deposited at pressures ranging from 0.86 to 10 mTorr, and magnetotransport measurements have been performed with the current both perpendicular to the plane (CPP) and in the plane (CTP) of the samples. X-ray-scattering studies indicate that the roughness of the interfaces is influenced by the presence of the Nb layers used to make electrical contact for the CPP measurements, as well as by the sputtering pressure. For samples deposited at higher sputtering pressures, the Nb contact layers also influence the low-temperature coercive field of the multilayers. The CPP-giant magnetoresistance is observed to decrease with increasing sputtering pressure and, in the case of the signal observed after cycling to above the saturation field, this decrease is found to come in roughly equal measure from an increase in the high field-saturated specific resistance and a decrease in the field-dependent specific resistance. Making use of the direct connection between microscopic physical parameters and experimental results available through the CPP geometry, we show that both of these changes arise primarily from increased scattering in both spin channels. We see very little, if any, evidence for a change in the spin-dependent scattering with sputtering pressure.