Magnetic and magnetoresistance studies of the evolution of the magnetic layer structure with Co layer thickness in electrodeposited Co–Cu/Cu multilayers

The structural transformation of electrochemically deposited Co–Cu/Cu multilayers with magnetic layer thickness was monitored via measurements of magnetization and magnetoresistance. For this, electrodeposition of [Co (tCo nm)/Cu (4 nm)]50 multilayers were carried out by varying the Co-layer thickness (tCo) down to 0.2 nm from a sulfate based single solution electrolyte. Magnetization measurements showed the appearance of anisotropy, increase in remanence magnetization and coercivity with systematic increase of tCo from 0.2 to 1 nm. Magnetic field direction dependent magnetoresistance (MR) measurements revealed that the isotropy in MR changes with tCo from tridimensional at 0.2 nm to in-plane at 0.4 nm to fully anisotropic at 1.0 nm. This illustrated that a fully granular magnetic Co-layer structure (tCo=0.2 nm) transforms into discontinuous layered one (tCo=0.4 nm) due to coalescence of suparparamagnetic regions to a continuous ferromagnetic layer (tCo=1 nm).