Complex Magnetoimpedance in Joule-Heated $Co_{71,1}Fe_{3,9}Si_{10}B_{15}$ Microwires

Complex magnetoimpedance study is an alternating current technique that can be used to probe some properties of magnetic materials. We report on complex impedance measurements in low-negative magnetostrictive ferromagnetic CoFeSiB microwire. In these wires, the domain structure consists of two parts: an inner core, with domains oriented to the longitudinal direction of the wire, and an outer shell with circumferentially oriented domains. This magnetic structure is modified by AC current flowing through the microwire which produces an additional circumferential magnetic field $H_Φ$ and significantly affects magnetic structure inside the wires. The additional circular magnetization process in wires was studied by impedance measurements as a function of the amplitude and the frequency of the AC current after gradual Joule heating. Changes in the magnetization processes are reflected in the real permeability values and loss factor values.