Magnetic field driving gradient effects on the microstructure in amorphous–nanocrystalline cobalt alloy ribbons

Abstract

Field effects on the early crystallization of Co-rich amorphous ribbons (Co(68.15)Fe(4.35)Si(12.5)B(15), atomic%) performed at 450 °C for 30 minutes in an applied 10 Oe longitudinal or transverse external magnetic field are investigated by comparing with the as-spun and annealed samples in zero applied magnetic field. Results indicate that the crystallization on the surface skin of the ribbon differs from that of the middle section due to the combined effects from the field direction and the defects or stress characteristics across the ribbons. In particular, the ribbons annealed under a transverse field exhibit an extremely distinct graded microstructure across the ribbon, which features amorphous-phased skin layers (top and bottom) of about 4-5 μm thickness and a middle amorphous-nanocrystalline composite layer about 10-12 μm thick, with the nanograins of 434 ± 99 nm dispersing in the amorphous matrix.

On the effect of cooling rate during melt spinning of FINEMET ribbons

“…It should be noted that bright halo rings observed in this pattern may be assigned to the very small volume fraction of nanocrystals that is not detectable with XRD due to the limited sensitivity of this technique. 23 The structure of annealed ribbons has also been investigated by TEM as depicted in Fig. 5c-e.…”

Optimization of GMI properties by AC Joule annealing in melt‐extracted Co‐rich amorphous wires for sensor applications

“…amorphous wires and ribbons, magnetic films, nanocrystalline wires, etc.) but also the featured GMI tailoring techniques by using proper postprocessing treatments including furnace annealing, Joule annealing, field annealing, laser annealing and tension annealing . It is necessary to select the proper annealing method for tuning the magnetic properties according to the geometric shape of sensitive materials, for ribbons the field annealing is more effective for the controlled magnetic anisotropy distribution and exchange coupling , while for wires one of mostly widely adopted is Joule annealing for amorphous wires based on previous reports , because the wire has good geometric symmetry and special magnetic domains, and strong circumferential anisotropy and suitable stress release under the current action can be induced.…”

Tunable Linear Dependence of Giant Magnetoimpedance Response of Microwires Annealed under Fluid Oil for Sensor Applications

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Generally, CoFe-based amorphous magnetic materials exhibit excellent soft magnetic properties such as the giant magnetoimpedance (GMI), effect which is promising for high-sensitivity sensor applications. [1][2][3][4][5][6][7] The GMI material for magnetic sensors demands high impedance ratio, high magnetic field sensitivity, and a large magnetic field response range to meet the detection requirement under different magnetic fields. However, it is a challenge to develop such a GMI material in the sensor field.

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