Low-field microwave magnetoimpedance in amorphous microwires

We have measured the low-field (<40 Oe) microwave losses in 5 mu m diam gla ss-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). Th ey exhibit well-differentiated hysteresis loops depending on the magnetostr ictive character of the alloy compositions [positive (FeSiBC), vanishing (C oMnSiB), and negative (CoSiB) magnetostriction] as a consequence of the par ticular magnetoelastic anisotropy distribution and hence the spontaneous do main structure. In the low-field region for which the microwires are not ma gnetically 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 l osses and the magnetization process of magnetically nonsaturated samples. ( C) 1999 American Institute of Physics. [S0021-8979(99)34408-X].