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

摘要

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 (t_(Co) nm)/Cu (4 nm)]_(50) multilayers were carried out by varying the Co-layer thickness (t_(Co)) 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 t_(Co) from 0.2 to 1 nm. Magnetic field direction dependent magnetoresistance (MR) measurements revealed that the isotropy in MR changes with t_(Co) 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 (t_(Co)=0.2nm) transforms into discontinuous layered one (t_(Co)=0.4nm) due to coalescence of suparparamagnetic regions to a continuous ferromagnetic layer (t_(Co)=1 nm).