Studies Of Giant Magneto-Impedance Effect In NiFeSiMoMn Alloy Films

In this thesis, three sets of Permalloy films have been prepared by DC magnetron sputtering deposition, which include NiFeSiMoMn single films, NiFeSiMoMn/Cu bilayer films and NiFeSiMoMn/Cu/NiFeSiMoMn sandwiched films. In order to increase the thickness and improve the quality of sputtered films, low deposition rate and 30nm Ta buffer layer on substrate have been adopted. As a result, 3 u m single films and 2.6 u m /2.6 u m 72.6 u m sandwiched films have been successfully prepared.With the increase of its thickness, the single film transforms crystal phase into amorphous phase. The sample is amorphous phase at the thickness 1000 nm, however, its soft magnetic properties gradually become worse. The phenomenon originates mostly from the thermal stress. The results also show the great improvement in anisotropy with the transverse applied field 800Oe. The soft magnetic properties have become better in samples annealed at 400 C for 1 hour in a transverse magnetic field of 15 Oe at vacuum atmosphere.The diffuse depths of copper in the sample deposited and the sample annealed at 400 C are 4.6nm and over 20nm respectively. We can conclude that the diffuse depth will be increased greatly with annealing temperature. The deposited bilayer films present better soft magnetic properties than the single layer films with the same thickness. Copper as a buffer plays an important role in improving the film quality. At the same time, the diffusion of copper in samples annealed at 400 C for 1 hour gives negative effect on the magnetic properties, however, the effect is not very evident.The sandwiched films with the structure of 2.5um/2um/2um and 2u m/2um/2 u m have been prepared by covered-module method. GMI effect will be studied in deposited and annealed samples with variation of magnetic field, driving frequency and current.