Study On The Preparation And Magnetic Properties Of Electroless-deposited NiFeP/Cu Composite Wires

Although early studies of GMI effect were focused on homogeneous materials,more attention has been paid to heterogeneous materials,especially in composite wires and sandwiched films.Compared with homogeneous materials,the GMI of heterogeneous materials is considerably enhanced.In addition,an obvious impedance change can be observed at much lower frequencies.In this work,NiFeP/Cu composite wires were prepared by electroless deposition.The influence of preparation conditions on magnetic properties and GMI effect was investigated comprehensively and systematically.The main conclusions are shown as follows:1.Optimization of plating conditions for NiFeP/Cu composite wires prepared by traditional electroless platingNiFeP/Cu composite wires were prepared by electroless deposition.The influence of the main parameters of the preparation process on GMI effect was investigated comprehensively and systematically.It turned out that these parameters had a significant effect on the magnitude and frequency dependence of GMI.Based on the above investigation,the optimal condition was further achieved with the mole ratio of FN=0.3,the NaH₂PO₂ concentration of 0.2 M,the pH of 11.5,and the plating temperature of 80°C.2.Giant magneto-impedance effect of NiFeP/Cu composite wires under optimal preparation conditionsUnder optimal conditions,the plating rate is about 18.6μm/h,keeping almost constant within the whole plating time.During the plating process,the variations of the Ni,Fe and P percentage in the layers are all small.Moreover,the samples both possess excellent soft magnetic properties.As a result,the GMI ratio of the optimal sample can reach 1103%.3.Giant magnetoimpedance effect of NiFeP/Cu composite wires prepared by chemical plating under DC currentNiFeP/Cu composite wires were prepared by chemical plating under DC current onto a Cu wire.The influence of the current magnitude on the surface morphology,magnetic properties and GMI effect was investigated.It was found that DC current has significant influence on GMI effect.As a result,the maximum GMI ratio of 1964%and the maximum field sensitivity of 463%/Oe were available at 50 mA,which only requires the preparation process of 15min.4.Giant magnetoimpedance effect of NiFeP/Cu composite wires prepared by chemical plating under AC currentChemical plating method of alternating current and intermittent alternating current were used to obtain NiFeP/Cu composite wires.A comparative study of the GMI effect of composite wires in different current forms was conducted.The results showed that the GMI effect of alternating current series samples is much lower than that of direct current samples.