Study of giant magneto-impedance behavior in Co-Fe based amorphous/nanocrystalline materials

Giant magneto-impedance (GMI) behavior have been studied in melt spun Co71-XFeXCr7Si8B14 ( X = 0, 2, 3, 2, 4, 6, 8, and 12 at%) alloys. The addition of Fe in the system changed the saturation magnetostriction constant from negative to positive values. The GMI property was measured with a driving current of 5 mA and 4 MHz frequency using a spectrum analyzer. The GMI ratio increased with the increase of the applied dc field and became maximum at a field H-k known as the anisotropy field of the materials. The maximum of GMI ratio (GMI(max)) depended on the Fe content and was maximum (12%) for Fe = 4 at% for the alloys in the as-melt spun state. Substantial increase of GMImax to 66% for Fe = 4 at% was observed after annealing the sample at 673 K.