Dependence of physical properties and giant magnetoresistance ratio on substrate position during rf sputtering of NiO and α-Fe2O3 for bottom spin valves

Abstract

The dependence of composition, crystalline orientation texture, surface roughness, and giant magnetoresistance (GMR) ratio on substrate position during rf reactive sputtering of antiferromagnetic NiO and α-Fe2O3 films for dc magnetron sputtered Co/Cu/Co bottom spin valves have been investigated. For substrate positions from the center to edge of the target, the GMR ratio increased from 13.5% to 19.8% for NiO and from 9.8% to 13% for α-Fe2O3. These significant enhancements of GMR ratio was found to correlate with a decrease of surface roughness, increase in crystalline texture, and a nearly bulk stoichiometry of the NiO and α-Fe2O3 thin films.