Study of Giant Magneto-Impedance Behavior in Co-Fe Based Amorphous/Nanocrystalline Materials

Giant magneto-impedance (GMI) behavior have been studied in melt spun Co_71-XFe_XCr₇Si₈B₁₄ (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 GMI_max to 66% for Fe = 4 at% was observed after annealing the sample at 673 K.