Effect of rapid annealing on magnetic properties and magneto-impedance of cobalt-based alloy ribbons

Abstract The effects of rapid annealing (RA) for 3, 7, 10, and 15 s on the crystallization and magnetic properties of cobalt-based alloy ribbons were studied. The Ribbons consisted of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Co</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>42</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Fe</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>28</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Cr</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">B</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Si</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>18</mml:mn> </mml:mrow> </mml:msub> </mml:math> and were fabricated by single-drum rapid cooling technology. The as-cast samples were soft magnetic materials with an initial permeability of 2.5 × 10 4 , a Curie temperature of about 103 °C, and a saturation magnetization of about 107 emu g −1 . DSC analysis showed that RA for 10 s at 500 °C produced a crystallinity of 42% and a saturation magnetization of 111 emu g −1 . The results showed that the crystallinity of about 20% at 7 s rapid annealing was most suitable for the largest magneto-impedance (MI) effect with a maximum MI ratio of 113% at 15 MHz. This result demonstrates the close correlation between the rapid annealing mode, crystallinity ratio and MI effect, contributing to the development of RA technology for amorphous soft magnetic alloys.