The magnetic field sensing performance of FeCo-based soft magnetic alloys with varying Fe/Co ratio

(FeCo)84CuB15 soft magnetic alloys with Fe/Co ratios (5:1, 3:1, and 1:1) were prepared using the planar flow casting method. The structural and magnetic properties together with magnetic field-sensing performance of the ribbons were investigated in detail. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the structural characterization. The magnetic parameters were determined by vibrating sample magnetom-eter and B-H loop tracer. The 2-D magnetic field variations on the surface of the ribbons were determined via a magnetic force microscope. The fluxgate sensors were prepared using the casted ribbons to test magnetic field sensing ability by measuring the second harmonic voltage induced in the pick-up coils by the lock-in amplifier. The working range and the noise of the sensors were also determined. The amorphous structure of the ribbons was confirmed by X-ray diffraction (XRD) patterns. The magnetic hysteresis measurements revealed the soft magnetic behaviour of the alloys having magnetization values as high as 1.3 T and coercivities around 1 Oe. As Fe/Co ratio increases, permeability values increase substantially. Meanwhile, the coercivities remained almost the same as close to 1 Oe. The alloys' magnetic field sensing feature decreased drastically as the Fe/Co ratio rose. Besides, noise parameters degraded. The linear response of the sensors to the external magnetic field (i.e., working range) enlarged with increasing Fe-content in the alloys.