Enhanced High-frequency Magneto-impedance Response of Melt-extracted Co69.25Fe4.25Si13B13.5 Microwires Subject to Joule Annealing

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Soft ferromagnetic wires, Joule annealing, Magneto-impedance, High frequency, Magnetic sensors

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We report an enhancement of low-field, high-frequency magneto-impedance (MI) response and circumferential domain structures of melt-extracted amorphous Co69.25Fe4.25Si13B13.5 microwires by dc Joule annealing. The current amplitudes of 5 mA, 10 mA, and 20 mA were applied to amorphous microwires for different time treatments. The magnetic field dependence of impedance and circumferential domain structure of the microwires were explored using an impedance analyzer over a high frequency range (20 MHz–1000 MHz) and magnetic force microscopy (MFM), respectively. Consequently, the optimum value of 5 mA current for 20 min markedly improved the MI ratio up to 610% (1.7 times of 380% from the as-cast state) at a working frequency of 20 MHz. Moreover, the magnetic field sensitivity has been achieved up to 500%/Oe (more than two times of 225%/Oe from the as-cast one) at a frequency of 40 MHz. MFM images clearly show the development of a well-defined circumferential domain structure of the annealed microwire comparing with the as-cast one. The improvement of the high-frequency MI response in Co-rich amorphous microwires is promising for sensitive magnetic microsensors for low field detection.

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Journal of Science: Advanced Materials and Devices, v. 1, issue 1, p. 69-74

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