GIANT MAGNETORESISTANCE OF ELECTRODEPOSITED CO/CU MULTILAYERS

We report on the structural and electrical characterization of electrodeposited Co/Cu multilayers grown in a single electrolyte based on CoSO4 and CuSO4. A high degree of crystallographic orientation and superlattice coherence is found in the growth on (100)- and (111)-oriented substrates. The magnetoresistance (MR), measured in the current-in-plane configuration at room temperature, is dominated by the giant MR effect for Cu-layer thicknesses d(Cu) greater than or similar to 3 nm and by the anisotropic MR effect for d(Cu) less than or similar to 2.5 nm. A maximum of 14% is measured for d(Cu) approximate to 4 nm. No evidence for antiferromagnetic coupling is found. Instead, the giant MR gradually diminishes with decreasing d(Cu) < 4 nm which is attributed to ferromagnetic coupling due to magnetic pinholes. The influence of the Cu2+-ion concentration, the addition of levelling agents, and the Go-and Cu-layer thicknesses on the structure and magnetoresistance is systematically investigated. Especially the use of levelling agents has a catastrophic effect on the structural quality of the multilayers and on the magnitude of the MR.