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

Abstract

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 (4nm)]50 multilayers were carried out by varying the Co-layer thickness (tCo) down to 0.2nm 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 1nm. Magnetic field direction dependent magnetoresistance (MR) measurements revealed that the isotropy in MR changes with tCo from tridimensional at 0.2nm to in-plane at 0.4nm to fully anisotropic at 1.0nm. This illustrated that a fully granular magnetic Co-layer structure (tCo=0.2nm) transforms into discontinuous layered one (tCo=0.4nm) due to coalescence of suparparamagnetic regions to a continuous ferromagnetic layer (tCo=1nm).