Low-field microwave magnetoimpedance in amorphous microwires

We have measured the low-field (<40 Oe) microwave losses in 5 μm diam glass-covered amorphous wires fabricated by the Taylor-Ulitovsky method at 9.8 and 32.5 GHz and their hysteresis loops at very low frequency (0.1 Hz). They exhibit well-differentiated hysteresis loops depending on the magnetostrictive character of the alloy compositions [positive (FeSiBC), vanishing (CoMnSiB), and negative (CoSiB) magnetostriction] as a consequence of the particular magnetoelastic anisotropy distribution and hence the spontaneous domain structure. In the low-field region for which the microwires are not magnetically saturated, as is typical in ferromagnetic resonance experiments, the microwave losses evolve with applied field in a similar manner to that of the magnetization process, and denote a correlation between microwave losses and the magnetization process of magnetically nonsaturated samples.