Primary beam energy dependence of properties in ion beam sputtered spin–valve films

Abstract

Spin–valve films with the structure Ta/NiFe/FeCo/Cu(18–30 Å)/FeCo/FeMn–70 Å/Ta were deposited using a Veeco ion beam deposition (IBD) system, model IBD-350. The physical properties of these spin–valve films as a function of primary ion beam energy have been studied in a primary ion beam energy range of 600–1500 eV. Xe was used as the working gas. The optimal ion beam energy range for the best spin-valve performance has been found to be around 600 eV. Giant magnetoresistance (GMR) values of ΔR/R∼8% have been measured for the spin–valve films deposited in this energy range. A strong dependence on beam energy of magnetic properties for these spin–valve films has been observed in the energy range from 600 to 1500 eV. ΔR/R for spin–valve films with a Cu layer thickness of 22 Å decreases from 7.5% at 600 eV monotonically to 6.1% at 1500 eV with increasing ion beam energy. Interlayer coupling field increases from 20 Oe at 600 eV to 37 Oe at 1500 eV. Further reduction in the interlayer coupling field to 13 Oe and an increase in ΔR/R to 8% have been achieved by depositing the free layer at 1000 eV and the rest of the layers at 600 eV. These are consistent with the improvement in crystallographic orientation and crystallinity of these spin–valve films.