Nonlinear Magnetoimpedance In NiFeSiMnMo/Cu/NiFeSiMnMo Multilayered Films

Recently, the Magneto Impedance effect (GMI) found in amorphous wires with soft magnetic properties is noticeable as a new principle for sensing magnetic filed. According to this effect, the impedance of the wire in the range of high frequencies over 10 MHz changes remarkably with the external magnetic field. This effect is expected to be promising for magnetic field sensor with high sensitivity. Therefore, we have attempted to introduce this effect into amorphous multilayered films to extend application fields. The films were deposited onto Si substrates by vaporizing plating, and the giant magneto-impedance effect has been investigated in multilayered films NiFeSiMnMo/Cu/NiFeSiMnMo annealed at 290°C for 4 h. The frequency and field dependences of the GMI have been observed in the frequency range from 50 KHz to 13 MHz. The GMI ratio increases at first with increasing frequency, and reaches its maximum value of 14.9% at a very low characteristic frequency of about 3 MHz, and then decreases with further increasing frequency. These superior properties are related to the special structure of the multilayered films. The maximum giant magneto-impedance ratios were also studied in the longitudinal and transverse fields, respectively. Then a novel multilayered films sensor sensitive to small magnetic field based on the Magneto Impedance effect has been proposed.The sensor consists of half bridge of the individual detecting element with NiFeSiMnMo/Cu/NiFeSiMnMo multilayered films, which exhibits the large impedance change ratio more than 43.5% when an external magnetic field is applied. No hysteresis, good linearity and good stability against temperature variation as well as high sensitivity in the sensor characteristics have been achieved.The soft magnetic properties and nonlinear giant magnetoimpedance (GMI) effect were investigated in multilayered NiFeSiMnMo/Cu/ NiFeSiMnMo with different thickness of NiFeSiMnMo films. The NiFeSiMnMo/Cu/ NiFeSiMnMo multilayer films prepared on the substrate of corning glass with a further thermal treatment of the final GMI elements. The large GMI ratio is correlated to thickness of NiFeSiMnMo film in the multilayered NiFeSiMnMo/Cu/ NiFeSiMnMo films. The use of thin film technology for GMI is preferable in many applications because of its compatibility with integrated circuit technology which enables miniaturization, avoiding alignment issues, and wire soldering. Maximum GMI sensitivities of 8.9%Oe~-1 and3.9% Oe~-1 were achieved in longitudinal and transverse fields, respectively.