Influence of sputtering pressure on the giant magnetoresistance and structure in Fe–Cu–Ni granular thin films

Composition, structure and giant magnetoresistance in Fe_xCu_yNi_z films prepared at different sputtering pressures were investigated. X-ray diffraction studies showed only Cu (1 1 1) peak from the Cu grain. The shifts in the d-spacing d₁₁₁ of Cu indicates a progressive substitution of Ni in the Cu lattice. Similar trends in d₁₁₁ of Cu observed for the samples prepared at different sputtering pressures indicate that the structural behaviour of the samples is nearly independent of the sputtering pressure. A significant enhancement of magnetoresistance (MR) for the samples sputtered at 0.001 mbar as compared to that sputtered at 0.02 mbar is attributed to the reduced role of residual gas impurities in the films upon lowering the sputtering pressure. An interesting observation is that the MR did not significantly decrease even with a large substitution of Ni in the Cu grains.