Giant Magnetoimpedance Effect Of Electroless-deposited NiFeP/BeCu Composite Wire

In this paper, we prepared the NiFeP/CuBe composited wires by electroless- deposition, and used different ways to anneal the samples. Then the giant magneto-impedance effect (GMI) of the NiFeP/CuBe composite wires were studied systemically. The results demonstrate that the different magnetic domain structures are important to the GMI effect of the composite wires.1, The NiFeP films are excel lently electro less-deposited on CuBe wire and the NiFeP/CuBe composite wire is hereby prepared.2, n order to get ideal GMI effect, the optimized condition of fabricating was studied. The composition of NiFeP film is dependent on the concentrations of Ni²⁺ and Fe²⁺ in NiFeP electroless-plating bath, which is vital to the GMI effect of the NiFeP/CuBe composite wires. The optimal conditions are as follow: FN = [Fe²⁺]/[Ni²⁺+Fe²⁺] = 0.7, and the composition of the composite wires is Ni₇₉Fe₁₅P₆. And when the CuBe wires were deposited for 1 hour in the bath, the thickness of the ferro-magnetic layer is about 1.5μm.3, Annealing techniques have great effects on the samples. DC Joule annealing can induce circular anisotropy, so as to increase the GMI effect of the samples; while stress annealing and annealed in a furnace can only induce longitudinal anisotropy, which will lead to the decrease of the GMI effect of the samples.4, NiFeP/CuBe samples are sensitive to the temperature. With the increase of the temperature, from anisotropy to nanocrystalline, and then the samples crystallized. Meanwhile, its prefered orientation changes.5, In certain condition, DC Joule annealing can induce circular anisotropy among the ferro-magnetic layer of the samples, thus increases the ratio of the GMI effect of the samples. When the current is lagerer than 2. 4A, the GMI effect of the samples enhance greatly. In the optimum condition tof annealing for 2minutes with 2.8A, when the drive frequency is 475KHz, the sample's highest value is 53.2%And meanwhile, obvious MI effect of NiFeP/CuBe composite wire is observed with the value of 26.5% at 50kHz.