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

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