The effect of annealing and crystallization on the magnetoelastic properties of Co Si B amorphous wires

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The field dependence of Young’s modulus (ΔE effect) of amorphous wires of Co72.5Si12.5B15 has been studied in the as-quenched state, and after annealing for times between one and several hundred minutes at temperatures of 450, 480, and 500 °C. In the as-quenched state the ΔE effect is small (<2%), because the quenching stresses couple with the magnetostriction (λs∼−3×10−6) to produce significant anisotropy. Annealing for short times (≳1 min) is sufficient to relieve much of the quenching stress, resulting in magnetic softening and enhanced ΔE effect (at best ≳30%). Further annealing eventually reverses these trends, increasing coercivity and anisotropy, and reducing the ΔE effect. This behavior is attributed to surface crystallization. The results are interpreted in terms of the core-shell domain model, and are consistent with the retention of a significant component of circumferential domain structure in the shell in all annealing conditions studied.