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

Spin-valve films with the structure Ta/NiFe/FeCo/Cu(18-30 Angstrom)/FeCo/Fe Mn-70 Angstrom/Ta were deposited using a Veeco ion beam deposition (IBD) sy stem, 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 bea m 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 Delta R/R simila r to 8% have been measured for the spin-valve films deposited in this energ y range. A strong dependence on beam energy of magnetic properties for thes e spin-valve films has been observed in the energy range from 600 to 1500 e V. Delta R/R for spin-valve films with a Cu layer thickness of 22 Angstrom decreases from 7.5% at 600 eV monotonically to 6.1% at 1500 eV with increas ing 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 Delta R/R to 8% have been achieved by depositin g 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 crysta llinity of these spin-valve films. (C) 1999 American Institute of Physics. [S0021-8979(99)27508-1].