Magnetostriction of Amorphous Magnetic Microwires: Role of Local Atomic Environment and Internal Stresses Relaxation

We studied the magnetostriction coefficients, λs, Curie temperature, Tc, and their dependence on annealing conditions in Fe47Ni27Si11B13C2 and Co67Fe3,9Ni1,5B11,5Si14,5Mo1,6 amorphous glass-coated microwires with rather different character of hysteresis loops. A positive λs≈20x10-6is observed in as-prepared Fe47Ni27Si11B13C2, while low and negative λs ≈-0.3x10-6 is ob-tained for Co67Fe3,9Ni1,5B11,5Si14,5Mo1,6 microwire. Annealing affects the magnetostriction coeffi-cients and Curie temperatures, Tc, of both Fe47Ni27Si11B13C2 and Co67Fe3,9Ni1,5B11,5Si14,5Mo1,6 glass-coated microwires in a similar way. Observed dependencies of hysteresis loops, λs and Tc on annealing conditions are discussed in terms of superposition of internal stresses relaxation and structural relaxation of studied microwires. We observed linear λs dependence on applied stress, σ, in both studied microwires. A decrease with applied stress is observed for Co-rich mi-crowires with negative magnetostriction coefficient. In contrast, a linear increase of the magne-tostriction coefficient with applied stress is observed for Fe-Ni- rich microwires with positive magnetostriction coefficient. Observed results are discussed in terms of influence of internal stresses and short range atomic rearrangements induced by annealing on hysteresis loops, magnetostriction coefficients and Curie temperatures of studied microwires.