Abstract
Amorphous ferromagnetic microwires have drawn attention primarily due to their excellent soft magnetic properties as the elements of sensors. In this work, semi-hard magnetic microwires of composition Fe4.3Co67.7Si11B14Cr3 were obtained after a process of directional crystallization from amorphous state. The XRD analysis of crushed and whole wires identified the formation of the face-centered Co-modification as the main phase of directionally crystallized core alloy, which explains a large increase in anisotropy and coercivity. The application of a magnetic field during crystallization may orient the easy anisotropy axis of crystallites along the wire. This is confirmed by the investigation of crystallite orientation with respect to the wire axis and X-rays direction in diffractometer. The obtained results revealed that the formation of crystallites in amorphous Co-rich microwires occurs with the predominant orientation of the crystallographic direction [111] along the wire axis and the direction of a magnetic field during the directional crystallization process.
Highlights
Amorphous soft ferromagnetic wires exhibiting fast magnetization reversal and giant magnetoimpedance are promising materials for developing sensitive sensors of weak magnetic field, current, mechanical stress for various applications including structural health monitoring
The wires after directional crystallization are fully crystalline, because there are no sharp peaks in their DSC curves
In the case of wires of type 4 which failed the directional crystallization (Fig.3), the intensity of the peaks decreases and the estimated average size of Co-phase crystallites is in the range of 1.7-1.8 nm, which can be regarded as existence of a quasi-amorphous state
Summary
Amorphous soft ferromagnetic wires exhibiting fast magnetization reversal and giant magnetoimpedance are promising materials for developing sensitive sensors of weak magnetic field, current, mechanical stress for various applications including structural health monitoring. After annealing treatment at temperatures close to the crystallization temperature, initially amorphous microwires change their structural and magnetic properties. The transformation from soft to hard magnetic properties was explained by the formation of crystallites of a hexagonal modification of cobalt [2] and their alignment along the wire during the crystallization process. A more detailed XRD analysis performed in [3] revealed the presence of face-centered modification of cobalt after the crystallization procedure, which could have cubic crystalline anisotropy. The mechanisms of coercivity and anisotropy increase in microwires after directional crystallization were investigated. A number of experiments with different orientation of the wire samples with respect to the measuring directions was carried out with the help of diffractometric and magnetometric methods
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