Controlling the magnetic properties of microwires by gradient annealing

Abstract

Abstract

Amorphous magnetic microwires offer a versatile platform for controlling domain structure and magnetic properties through annealing.. Thus, bending annealing yields to obtain a previously unobserved form of magnetic bistability influenced by the bending radius, with magnetization reversal accompanied by rapid domain wall, DW, motion. Spiral annealing represents another powerful post-processing technique that enables the onset of both transverse and longitudinal stress gradients by shaping the sample during the annealing, thereby producing graded magnetic anisotropy directly influencing DW dynamics. Magneto-optical demonstrate a correlation between the anisotropy field and local curvature. Furthermore, spiral annealing facilitates the stabilization of specific domain structures, including helical configurations, within defined curvature ranges. The preservation of stress-induced anisotropy distribution after straightening the sample is of particular importance for technological applications. Complementary studies on bent microwires demonstrate that transverse stress gradients across the wire diameter lead to the coexistence of axial, elliptical, and spiral domain structures on different sides of the wire. Stress-annealing with a controlled temperature gradient enables the formation of graded magnetic anisotropy along the microwire allowing for spatial control of DW dynamics, including acceleration, deceleration, and even DW trapping in regions with high enough induced anisotropy. The induced transverse anisotropy influences DW propagation in a manner analogous to the effect of an applied transverse magnetic field, resulting in a decrease in DW length and a change in its mobility.. Furthermore, torsion-induced anisotropy offers an additional means of controlling characteristics by introducing asymmetry into magnetic and impedance properties, leading to enhanced magneto-impedance sensitivity and improved response linearity. These findings underscore the significance of local stress distribution in determining magnetization reversal behavior and domain configuration. A variety of domain structures can be obtained by annealing under temperature or stress gradient. Collectively, these approaches provide a comprehensive toolbox for designing advanced magnetic microwire-based devices. .