Effect of annealing on the characteristics of Au/Ni80Fe20 and Au/Ni30Fe70 bilayer films grown on glass

Au/Ni80Fe20 and Au/Ni30Fe70 bilayer films obtained by electron beam evaporation and sputtering were annealed in a vacuum of 5×10−4 Pa from 100 to 350 °C for 15 and 30 min, respectively. Auger electron spectroscopy (AES) was used to analyze the composition inside the Au layers. X-ray diffraction (XRD) was used to analyze the structural characteristic of the bilayer films. The sheet resistance of the bilayer films was measured using four-point probe technique. No impurity such as carbon, nitrogen, oxygen, sulphur and chlorine was detected inside the Au layers. As the annealing temperature and time changed from 150 °C, 15 min to 350 °C, 30 min, the Ni atoms in the Au/Ni80Fe20 bilayer films diffuse preferentially into the Au layer while a significant diffusion of Fe atoms in the Au/Ni30Fe70 bilayer film into the Au layer was observed. The diffusion of Ni and/or Fe atoms into the Au layer results in an increase in the resistivity of the bilayer film. Large numbers of Ni atoms diffusing into the Au layer of the Au/Ni80Fe20 bilayer film result in a remarkable decrease in the lattice constant of the Au layer.