Magnetic and electric property evolution of amorphous cobalt-rich alloys driven by field annealing

Abstract

Microstructure changes of the cross-section of Co-rich amorphous ribbons (Co68.15Fe4.35Si12.5B15, atomic%) annealed at 450 °C for 30 min with a zero field, a 10 Oe longitudinal external magnetic field or a 10 Oe transverse external magnetic field are investigated by comparing with as-spun ribbons. The ribbons annealed without a field, and under the transverse or longitudinal field exhibit different gradient microstructures along the cross-section of the ribbons, forming gradient amorphous–nanocrystalline (AN) composites different from the as-spun amorphous species. These kinds of AN composites preserve unique magnetic properties and enhanced conductivities when compared with the as-spun ribbons, leading to excellent giant magneto-impedance (GMI) effects. In particular, the AN composites prepared from the ribbons annealed under the longitudinal field lose the dual-peak feature shown by the as-spun ribbons but a mono-GMI peak appears, preserving a maximum MI ratio as high as 520% and a low magnetic field (0–1 Oe) sensitivity of 80% Oe−1 at 15 MHz and a maximum field of 40 Oe. The distinctly graded AN composites prepared from the ribbons annealed under the transverse field still preserve the dual-peak feature as the as-spun ribbons, having a maximum MI ratio of 320% and a significantly enhanced low magnetic field (0–1 Oe) sensitivity of 200% Oe−1 at 10 MHz and a maximum field of 40 Oe.

Magnetoimpedance Effect in Field Annealed (FeNi)_{78}Nb_{7}B_{15} Amorphous and Nanocrystalline Bilayer Ribbons

“…Here, two maxima are observed at the positions where the external dc magnetic eld, applied in the longitudinal direction, reaches the transverse anisotropy eld, ±H k . On the other hand, longitudinal magnetic anisotropy induced by LF-annealing, leads to single peak behaviour of the magnetoimpedance, in accordance with [6]. Figure 2 shows the measured ∆Z/Z(H) dependences for mono and bilayer ribbons after eld annealing at 673 K in longitudinal magnetic eld.…”

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.…”

A General Strategy for Nanohybrids Synthesis via Coupled Competitive Reactions Controlled in a Hybrid Process

“…Composition and strucrue controlled hybridization has become an effective approach for realizing multi-functionality, stability and/or producing new physicochemical properties of nanomaterials due to the surface and interface enhanced properties and the synergistic effect among components 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 . With the advancement of science and technology promoted by nanohybrids, large scale, controlled-engineering of nanoparticles (NPs) becomes more and more urgent to fulfill their academic and industrial perspectives 3 10 25 26 27 28 29 30 31 32 .…”