Design of the Magnetic Properties of Fe-Rich, Glass-Coated Microwires for Technical Applications


  • Useful discussions with Prof. J. González, Dr. V. Zhukova, V. Larin, and Dr. J. M. Blanco, and the technological support of Tamag Ltd. and AmoTec Ltd. are gratefully acknowledged. This work was supported in part by the Spanish Ministry of Science and Technology under Grant MAT2004-05348-C04-04.


The magnetic anisotropy of Fe-rich, thin, amorphous wires is tailored by stress annealing (SA). In particular, the effect of conventional annealing (CA) and SA on the magnetic properties of Fe74B13Si11C2 glass-coated microwires is studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain SA conditions (annealing temperature, Tann > 300 °C; applied stress, σ > 400 MPa), a transverse magnetic anisotropy is induced: a rectangular hysteresis loop transforms into an inclined one at magnetic-anisotropy fields above 1000 A m–1. Under tensile stress, the rectangular hysteresis loop of microwires annealed using SA is recovered. Samples subjected to SA show noticeable magnetoimpedance and stress-impedance effects, despite their large magnetostriction. The samples obtained exhibit a high stress sensitivity of their giant magnetoimpedance (GMI) effect and hysteretic properties, allowing the use of the obtained samples in magnetoelastic sensors, and for designing stress-sensitive, tunable composite materials. By varying the time and temperature of such SA, we are able to tailor both the magnetic properties and the GMI of Fe-rich microwires.