Effect of annealing on characteristics of Ni48Fe12Cr40/Ni80Fe20 bilayer films deposited on Si(1Â 0Â 0)/SiO2 by electron beam evaporation

Ni48Fe12Cr40(7 nm)/Ni80Fe20(40 nm) bilayer films and Ni80Fe20(40 nm) monolayer films were deposited at ambient temperature on Si(1 0 0)/SiO2 substrates by electron beam evaporation. The effect of annealing on the structure, composition, magnetization and magnetoresistance of the Ni48Fe12Cr40/Ni80Fe20 bilayer films was investigated. The structure of the Ni48Fe12Cr40/Ni80Fe20 bilayer films remains stable for annealing temperature up to 280 °C. For the as-deposited bilayer film the introducing of the Ni48Fe12Cr40 underlayer promotes both the [1 1 1] texture and grain growth in the Ni80Fe20 layer. The annealing promotes the grain growth of the Ni48Fe12Cr40/Ni80Fe20 bilayer films when the annealing temperature exceeds 280 °C. After annealing at a temperature over 280 °C, Cr atoms inside the Ni48Fe12Cr40 layer diffuse into the Ni80Fe20 layer and segregate on the surface of the Ni80Fe20 layer. The Ni48Fe12Cr40 underlayer as a seed layer can enhance the anisotropic magnetoresistance ratio of the Ni80Fe20 layer at a annealing temperature up to 280 °C compared with Ni80Fe20 monolayer film. After annealing at a temperature over 280 °C, however, the anisotropic magnetoresistance ratio of the Ni80Fe20 monolayer films exceeds that of the Ni48Fe12Cr40/Ni80Fe20 bilayer films. For all annealing temperatures, the coercivities of the Ni48Fe12Cr40/Ni80Fe20 bilayer films are smaller than those of the Ni80Fe20 monolayer films.