Giant Magneto-Impedance Of NiFe/Cu And NiFeMo/Cu Composite Wire Produced By Pulsed Electrodeposition

With the development of society and technology, more and more information equipments will be used, so the request for the properties of magnetism sensor has been becoming higher and higher. The new type magnetism sensor must be minitype, quick response, high sensitivity and good stability. Giant magneto-impedance(GMI) effect is the phenomenon that the impedance of material can be dramatically changed by the applied static magnetic field. Sensors made by giant magneto-impedance materials can meet the demands of high sensitivity,micro-size,quick response,low power consuming,no contact detecting and no hysteresis. Furthermore, this kind of sensors are driven by AC current, so that one can easily realize many functions in using them, such as modulating, demodulating, filtering of the wave, oscillation and resonance. So giant magneto-impedance effect will have a good view in applied in high sensitivity magnetism sensor and head. The Ni-Fe alloy has excellent soft-magnetism properties, so the GMI effect is expected to abtain in this material.Pulsed electrodeposition was adopted to make NiFe composite wires in this work, Mossbauer spectroscopy, XRD, TEM, SEM and AGM were used to explore the micro-structure and magnetism properties of the samples. The GMI effect was measured by the GMI measurer.Pulsed electrodeposition was performed by using vitriolic plating with given mixture ratio. We have prepared several groups of samples by changing pulse frequency, plating time, magnitude of deposit current etc. then explore the effect on the GMI of different samples.We found that the surface of composite wires are very smooth and compaction. The grain size of film is in the range of 15nm-40nm, and it varied regularly with parameters of pulsed electrodeposition; As the parameters of pulsed electrodeposition changed, the film was found to be NiFe alloy and FeNi3 alloy respectively; the GMI effect of samples that prepared at low pulse frequency is always better than that prepared at high pulse frequency, it is because of the different stress at different frequencies; The thickness of the film increases with increasing of plating time, but the GMI effect doesn't, experiment show that when the thickness of the film is in the range of 6μm to 11μm, the GMI effect of sample is very excellent and the maxmin GMI ratio is more than 250%; Dimension of deposit current has a influence on magnetic anisotropy of the film, it makes film generate transverse magnetianisotropy, and the transverse magnetic anisotropy is the most important factor affecting GMI effect.The GMI effect of samples these prepared in this experiment is more than 100% basically, and it reaches the highest value as 428% under the following conditions: frequency of 500Hz, y of 20%, plating time of 10 minutes,driving frequency of 30KHz.NiFeMo/Cu composite wire is prepared in this experiment too, we found that as the increasing of Mo content in the bath, the film change from crystalline state to amorphous state. The maxmin GMI ratio is 83% when driving frequency is 600KHz.