Magnetic Properties Modulation Of Fe-based Ribbons By Permalloy Films Coating

In recent years, researchers found out that soft magnetic material surrounded by conductive or magnetic materials could change or modulate its magnetic properties, the interaction between them is yet to be further studied. Meanwhile, Giant magneto-impedance (GMI) effect has been applied in weak magnetic sensors, and has been developed into one of the research tools to investigate soft magnetic materials. To systematically study magnetic interaction between the magnetic materials, we prepared Ni80Fe20 layer coated on free surface/wheel surface of amorphous/ FINEMET ribbon and sandwich structured amorphous/FTNEMET ribbon by RF magnetron sputtering. We discussed the surface topography, GMI effect and hysteresis loops, and main conclusions are shown as follows:1. Three series of Ni80Fe20 layer coated on free surface/wheel surface of amorphous ribbon and sandwich structured amorphous ribbon.For the series of Ni80Fe20 layer coated on free surface of amorphous ribbon, GMI effect first increased and then decreased with Ni80Fe20 layer thickness growing, and when it reaches to 260nm, GMI ratio got to the highest 33%. This conclusion coincides well with the surface topography. It can be interpreted that 260nm thick Ni80Fe20 layer and amorphous ribbon both possess transverse magnetic structure, which leads to the strongest magnetic interaction between them, thus contributing to enhance magnetic properties. For the series of Ni80Fe20 layer coated on wheel surface and sandwich structured of amorphous ribbon, GMI effect of the sample with 260nm thick Ni80Fe20 layer was the highest resulted from magnetic interaction. The GMI ratio of 260nm sandwich structured sample was largest, which was due to the interaction between ribbon and two layers were both strong.2. Three series of Ni80Fe20 layer coated on free surface/wheel surface of FINEMET ribbon and sandwich structured FINEMET ribbon.By measuring GMI effect of three series samples, we concluded 260nm Ni80Fe20 thick layer coated on free surface/wheel surface of FTNEMET ribbon and sandwich structured FINEMET ribbon showed the highest GMI ratios in its series, separately. Because 260nm thick Ni80Fe20 layer and FINEMET ribbon both possess transverse magnetic structure, which leads to the strongest magnetic interaction between layer and ribbon. The sandwich structured sample had the largest GMI ratio compared to the other two, which was owing to the interaction between ribbon and two layers were both strong. Compared to Ni80Fe20 layer coated on wheel surface, double-peak GMI profile of it coated on free surface showed better symmetry maybe depending on the surface roughness.