Magnetostriction of amorphous Co-based and Fe-Ni-based magnetic microwires: Effect of stresses and annealing

The magnetostriction coefficient and its stress dependence are evaluated in Co- and Fe-Ni- based glasscoated microwires with different character of hysteresis loops. The hysteresis loops as well as the magnetostriction coefficients of the microwires depend mostly on the chemical composition of the metallic nucleus. We found that the stress dependence of the magnetostricition coefficient, lambda s, is linear for both families of studied microwires, however a decrease with applied stress is observed for Co-rich microwires with negative magnetostriction coefficient. In contrast, a linear increase of the magnetostriction coefficient with applied stress is observed for Fe-Ni rich microwires with positive magnetostriction coefficient. Additionally the lambda s - value is affected by annealing. We evaluated the dependence of lambda s on annealing time, tann, for different annealing temperatures. In Co-rich microwires a change of the lambda s sign is observed. For both kinds of microwires (either with positive or with negative lambda s) lambda s(tann) at Tann = 400 degrees C present similar features: an increase with tann up to tann approximate to 10 min followed by a decrease for tann > 10 min. The lambda s(tann) dependencies are affected by the annealing temperature. Observed results are discussed in terms of influence of internal stresses and short range ordering induced by annealing. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).