Low temperature effect on magnetic conversion and giant magnetoresistance in electrodeposited CoCu/Cu multilayers

In the present study, the variation of superparamagnetic (SPM) and ferromagnetic (FM) components and their effect on giant magnetoresistance (GMR) in electrodeposited CoCu/Cu multilayers (ML's) were investigated in the temperature range 30–300 K. For this, two different kinds of ML's, one with discontinuous Co-layer consisting of large superparamagnetic (SPM) (tCo = 0.2 and 0.3 nm) fractions and the other with continuous Co-layer containing large ferromagnetic (FM) (tCo = 2 and 3 nm) content were considered. Magnetoresistance measurements showed increase in MR magnitude with decrease in temperature associated with magnetic conversions in the magnetic Co-layers. At 300 K, a substantial difference in magnitude of MR was found for multilayers with tCo = 0.3 (5.07%) and 3 nm (8.82%). However, at 30 K very close values of MR for multilayer pair with tCo = 0.3 (16.48%) and 3 nm (17.72%) ensures a significant transformations of SPM to FM fractions in Co-layer at tCo = 0.3 nm. Similar results were obtained for the other pair of ML's i.e. tCo = 0.2 and 2 nm. This study suggests a suitable minimization of SPM content in the Co-layer could be another effective mechanism in maximizing the MR value. The measured temperature dependence of MR obeyed a simple T1 law