Giant Magneto-impedance Effect Of Graphene Composite Soft Magnetic Materials

The giant magneto-impedance(GMI)effect has attracted much attention since it was discovered in Co-based amorphous wire in 1994.Compared with traditional magnetic sensors,GMI sensors have several obvious advantages,including high sensitivity,remote query and low manufacturing costs.GMI sensor sensing components are usually composed of soft magnetic materials with high magnetic susceptibility and low coercivity.When there are other conductive or magnetic materials around the soft sensitive components,its GMI effect and magnetism will change.Many researchers have reported that magnetospheric coating on amorphous or nanocrystalline ribbon results in large variations in the GMI ratio.However,there are relatively few studies on the adjustment of the magnetic properties of nanocrystalline ribbons by conductive coatings.Therefore,it is necessary to study the influence of conductive materials on sensitive magnetic components.Moreover,in the multilayer structure,the inductance of the outer ferromagnetic layer is greater than the resistance of the inner conductive layer,so different GMI responses also occur.Therefore,we hope to find a new material with high conductivity to synthesize multilayer composite materials,hoping that GMI can have a more obvious response.Lightweight carbon materials have many advantages.One of the star materials,graphene,is expected to perform well in GMI sensitive components.Different graphene and different structures have significant influence on the GMI effect of soft magnetic composites.However,the researchers found that the roughness and internal stress of the composite nanocrystalline ribbons synthesized by transfer of CVD graphene,coating and other techniques would affect the GMI performance of the composite ribbons.Therefore,the main contents and results are as follows:1.In order to optimize the GMI effect and reduce the roughness of composite ribbons,the GMI effect of graphene composite soft magnetic material was explored.On the nanocrystalline Fe_73.5Cu₁Nb₃Si₁₃B_9.5 ribbon(FINEMET),the inner layer of reduced graphene oxide(rGO)was synthesized by electroless plating,and the outer layer of Fe Co was obtained by magnetron sputtering.By controlling the Fe Co layer thickness,the best sandwich structure Fe Co/rGO/FINEMET/rGO/Fe Co(/F/GFC)composite ribbon was obtained.When the concentration of graphene oxide(GO)was3 mg/100 m L,the solution p H value was 12.5,the concentration of hydrazine hydrate was 1.5 m L/16 m L,the electroless plating reaction temperature was 90?,the reaction time was 60 min,and the Fe Co layer thickness was 40 nm,the GMI effect of/F/GFC reached 70.32%,which was 2.1 times of the bare FINEMET ribbon,1.4 times of the FINEMET/rGO composite ribbon and 1.2 times of the FINEMET/Fe Co composite ribbon.The experimental results were explained by the regulation of magnetic properties of soft magnetic materials by magnetic dipole interaction.It provided a potential idea for the application of graphene composite magnetic materials in magnetic sensors.2.In order to avoid the impurities introduced by electroless plating and improve the quality of graphene and GMI effect,the GMI effect of chemical vapor deposition(CVD)graphene composite soft magnetic materials were explored.Graphene was directly grown on nanocrystalline ribbons by CVD method,and the optimum growth conditions were explored.Experimental results showed FINEMET/G composite ribbon were successfully prepared by using PMMA as carbon source.In addition,the Ni layer was used as a graphene growth transition layer by magnetron sputtering,and the FINEMET/Ni/G prepared when the Ni thickness was 300 nm at a growth temperature of 560?obtained the best GMI effect enhancement.This enables the direct growth of CVD graphene on FINEMET to synthesize GMI materials.