Improvement of Giant Magnetoimpedance and Sensitivity in Co68.5-xFe4WxSi16.5B11 (x = 0.8, 2) Ribbons Sandwiched in PVA/Fe3O4 Nanocomposite Films

In this work, giant magnetoimpedance (GMI); magnetic hysteresis loop; and sensitivity of Co68.5Fe4Si16.5B11 (S), Co67.7Fe4W0.8Si16.5B11 (W1), and Co66.5Fe4W2Si16.5B11 (W2) are comparatively studied for evaluating the effect of tungsten (W) on cobalt-based ribbons. At the frequency of 4.5 MHz and current of 25 mA, the values of GMI and sensitivity of W1 and W2 ribbons are, respectively, 105% and 36%/Oe, and 97% and 68%/Oe, so they are significantly enhanced as compared to S ribbons. Next, iron oxide (Fe3O4) nanoparticles are synthesized using the co-precipitation method, and polyvinyl alcohol-Fe3O4 (PVA/Fe3O4) nanocomposite films are prepared by dispersing Fe3O4 nanoparticles with weight ratios of 1–9% in the PVA solution. Then, magnetic properties and sensitivity of W1 and W2 ribbons are studied in the presence of PVA/Fe3O4 nanocomposite films with different ratios on both sides of the ribbons as well as in the absence of PVA/Fe3O4 nanocomposites. The results reveal that by increasing Fe3O4 weight ratio in PVA, the GMI and sensitivity of sandwiched ribbons increase remarkably as compared to ribbons free of PVA/Fe3O4 nanocomposite films. The maximum values of GMI and sensitivity are observed in the W1 ribbon covered with 7% nanocomposite, and sensitivity is enhanced up to 91%/Oe as compared to non-covered ribbons. These results present a new efficient method for increasing GMI and sensitivity in biosensor applications.