Effect of Substituting Hf for Zr on Fe-Co-M-Nb-B (M = Zr, Hf) Amorphous Alloys with High Saturation Magnetization

The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreover, the optimum ratio of Fe/Co was determined after the survey on different alloys with varying Fe/Co ratio resulting in the maximum saturation magnetization while keeping the coercivity low. After optimization, the highest saturation magnetization of 1.62 T was achieved with coercity of 11 A/m. While substitution of Hf for Zr slightly reduced the crystallization onset temperature of the amorphous structure, the thermal stability of the soft magnetic amorphous alloys was not significantly affected by the Zr/Hf replacement.

Giant Stress Impedance Magnetoelastic Sensors Employing Soft Magnetic Amorphous Ribbons

Soft magnetic amorphous alloys obtained via rapid quenching techniques are widely employed in different technological fields such as magnetic field detection, bio labeling, non-contact positioning, etc. Among them, magnetoelastic applications stand out due to excellent mechanical properties exhibited by these alloys, resulting from their amorphous structure, namely, their high Young modulus and high tensile strength. In particular, the giant stress impedance (GSI) effect represents a powerful tool to develop highly sensitive magnetoelastic sensors. This effect is based on the changes in the high-frequency electric impedance as the result of the variation in magnetic permeability of the sample under the action of mechanical stresses. In this work, the GSI effect is analyzed in two soft magnetic ribbons ((Co0.93 Fe0.07)75 Si12.5 B12.5 and (Co0.95 Fe0.05)75 Si12.5 B12.5) for the subsequent development of two practical devices: (i) the characterization of the variations in the cross-section dimensions of irregularly shaped elements, and (ii) the design of a flow meter for measuring the rate of flow of water through a pipe.