Preparation Of The CoP/Insulator/BeCu Composite Wire And Study Of Its Giant Magneto-impedance Effect

In this dissertation,2 types CoP/Inulator/BeCu composite wires,the ordinary type and the LC resonance type,have been prepared by electroless deposition.The methods of deposition rate measuring,impedance analysis,complex permeability, simple equivalent circuit model were employed to study the influences of the variable factors on GMI ratio and field sensitivity,such as process conditions,geometry and aftertreatment conditions.The main contents and results are included as follows:1.CoP soft magnetic alloy was deposited on polyster-coated BeCu wire using the optimum conditions.The solution comprise:I=x(H₂PO₂^-):x(Co²⁺)=8.0,complexing agent 0.5 mol/L,ammonium sulphate 0.25 mol/L.The operation conditions are:pH 9.0,temperature 90℃,time 3h.2.The ordinary composite wire was treated with two-step joule heating.The sample presents notable GMI effect after annealing.Its GMI ratio dramatically increases from 179%to991%and field sensitivity from 0.56%/A·m^-1to 2.78%/A·m^-1,respectively. So two-step joule heating is the effective way to significantly improve the GMI performance.3.The GMI ratio is 487.5%and field sensitivity of 0.46%/A·m^-1in the LC resonance type composite wire,which are both higher than 94.1%and 0.12%/A·m^-1in the ordinary type composite wire at the resonance frequency.Based on the characteristics of the LC resonance composite wire,a simple equivalent circuit model was proposed to simulate experimental curves.The simulated results agreed well with the experimental results.The physical mechanism of LC resonance type GMI is that the local resistance R₁,R₂ and the local inductance L₁,L₂ change with the extemal field, appearing as magneto-resonance resistance vary and magneto-resonance frequency shift.4.The capacitance,the local resistance R₁,R₂ and the local inductance L₁,L₂ change with the geometry modifying and the heat treating.Consequently,it radically influences the LC resonance type GMI.