Exchange coupling and giant magnetoresistance in electrodeposited Co/Cu multilayers

We present the results of the transport and magnetization measurements of electrodeposited Co/Cu multilayers grown in a single electrolyte based on CoSO4, H3BO3 and CuSO4. The samples are deposited on glass substrate covered by a 500 Angstrom thick Cu buffer layer. X-ray diffraction performed on the samples shows fee structure of both Co and Cu layers with preferential (111) orientation. Resistivity measurements show a giant magnetoresistance effect of about 4% at room temperature for multilayers with Co and Cu thickness between 4 nm I t(Co) less than or equal to 6 nm and 3 nm less than or equal to t(Cu) less than or equal to 4 nm respectively. For Co thickness t(Co) less than or equal to 1.5 nm, the magnetoresistance completely vanishes indicating that there is no more continuous Co layer. The indirect antiferromagnetic exchange coupling between magnetic Co layers is relatively large for 4 nm thick Cu spacer layer and gives rise to a temperature dependence of about 30 % between room temperature and 4.2 K.