Magnetoinductance Effect in Co<sub>67</sub>Fe<sub>4</sub>Si<sub>14.5</sub>B<sub>14.5</sub> Amorphous Ribbons Annealed With Different Orientation Magnetic Fields

Abstract

Magnetoinductance (MI) elements were constructed by winding a single coil on Co67Fe4Si14.5B14.5 amorphous ribbons fabricated by a single-roller melt-spinning technique. The effect of annealing methods on magnetic properties of amorphous ribbons was investigated. It was found that saturation magnetization, coercive force, and effective permeability of Co-amorphous ribbons were further improved by applying a magnetic field during annealing process. MI effect was evaluated by measuring the inductance under the magnetic field along the axis of MI elements. Experimental results showed that MI effect exhibited a characteristic of single peak curve and decreased with external magnetic fields regardless of the annealing methods. Although MI effect also decreased with frequency, the effect of frequency on MI effect was quite different for amorphous ribbons annealed with different processes. At the low frequency of 100 Hz, both the maximum inductance of $\sim 3.5\times 10^{-4}$ H and maximum magnetic field sensitivity of $\sim 37$ %/(A/m) belonged to MI elements with the ribbons annealed with the longitudinal magnetic field (LF). But at higher frequencies like 200 kHz, the annealing treatment LF was unexpectedly deteriorated to MI effect and the inductance and sensitivity of MI elements with the ribbons annealed longitudinal magnetic fields were even lower than those of MI elements with the as-quenched amorphous ribbons. By applying a transverse magnetic field during annealing process for amorphous ribbons, MI effect was always improved at all testing frequencies. The results were analyzed in terms of magnetic properties and magnetization process.