Manipulation of magnetic properties of glass-coated microwires by annealing A. Zhukov a,b,n , K. Chichay c , A. Talaat a , V. Rodionova c,d , J.M. Blanco e , M. Ipatov a , V. Zhukova a a Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, 20009 San Sebastian, Spain b IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain c Immanuel Kant Baltic Federal University, 236041 Kaliningrad, Russia d National University of Science and Technology (MISIS),119049 Moscow, Russia e Dpto. Física Aplicada, EUPDS Basque Country University UPV/EHU, Spain article info Article history: Received 12 June 2014 Received in revised form 30 September 2014 Accepted 2 October 2014 Available online 7 October 2014 Keywords: Thin wires Magnetic anisotropy Giant magnetoimpedance Domain wall propagation abstract We demonstrated that magnetic properties (hysteresis loops, domain wall propagation and giant magnetoimpedance effect) of Fe and Co-rich amorphous microwires can be tailored by stress and conventional annealing. Observed dependences discussed considering stress relaxation, back stresses and change of the magnetostriction after samples annealing. These considerations have been proved by experimental observation of the change of the magnetostriction coefficient sign induced by annealing. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Studies of amorphous magnetically soft glass-coated micro- wires have attracted considerable interest in the field of applied magnetism because of their reduced dimensionality (metallic nucleus diameter ranging between 0.5 and 30 μm), cheap and simple fabrication method and outstanding soft magnetic proper- ties [1,2]. From the applications point of view the most attractive properties of these materials are excellent soft magnetic proper- ties and giant magnetoimpedance, GMI, effect usually observed in Co-rich compositions and the magnetic bistability and fast domain wall propagation typical for Fe-rich compositions [1,2]. Magnetic sensors developed using amorphous wires with GMI effect allow achieving of pT magnetic field sensitivity with low noise [3]. High circumferential permeability usually exhibited by Co-rich amor- phous wires with vanishing magnetostriction constant is essential for observation of high GMI effect [1]. The Fe-rich amorphous wires are also proposed for various applications in the electronic article surveillance, magnetic tags, magnetic memories and logics [4–7]. Magnetic bistablility typical for Fe-rich glass-coated micro- wires has been interpreted in terms of depinning of the reversed domains inside the internal single domain and the consequent fast domain wall, DW, propagation [1,4]. Naturally the DW speed is one of most important factors affecting the viability of aforementioned potential applications. As reported elsewhere amorphous and nanocrystalline microwires exhibit extremely high DW velocity [4,8,9]. Generally hysteretic magnetic properties of amorphous ferro- magnetic microwires are affected by the magnetostriction coeffi- cient, λ s , and by the strength of internal stresses, s i , induced by glass-coating affected by the ρ-ratio of metallic nucleus diameter, d, to the total microwire diameter, D (ρ ¼ d/D) [1]. The origin of the internal stresses is related to the fabrication method of glass- coated microwires involving rapid solidification of composite microwire from the melt [1]. Consequently annealing has been successfully used for optimization of magnetic properties of glass- coated microwires [10,11]. Usually the effect of annealing is discussed considering the magnetoelastic energy, K me ¼ 3/2 λ s s (where s the total stresses, s ¼ s appl þ s i ,, s appl are applied stresses) [11,12]. Vanishing λ s values can be achieved in amorphous Fe–Co based alloys with Co/Fe E70/5 [12,13]. Moreover low magnetostrictive compositions exhibit stress dependence of the Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2014.10.003 0304-8853/& 2014 Elsevier B.V. All rights reserved. n Corresponding author at: Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, 20009 San Sebastian, Spain. Fax. 34 943017130. E-mail address: arkadi.joukov@ehu.es (A. Zhukov). Journal of Magnetism and Magnetic Materials 383 (2015) 232–236