Low-Field Microwave Phenomena in CoFeSiB Amorphous Magnetic Microwires

Metallic microwires with ferromagnetic nature and amorphous structure have been prepared by rapid solidification and drawing. Their alloy composition and thickness, 1 to 30 micron diameter, can be tailored to exhibit outstanding properties. Particularly, non-magnetostrictive CoFeSiB alloy microwires exhibit giant-magnetoimpedance effect while FeSiB alloy microwires show quite large Barkhausen magnetic jump. These properties make them very useful as sensing elements in particular magnetic, stress or temperature sensor devices. After presenting the general characteristics of investigated microwires, we introduce and analyse novel results about microwave absorption phenomena of such microwires in the low-DC field regime ( units or tens of Oe). We have used two alternative techniques: i) Absorption measurements as a function of DC applied low-field using a spectrometer operating at X-band frequency of 9.8 GHz, and ii) Ferromagnetic resonance measurements in a network analyzer in the frequency range up to 20 GHz for different DC applied fields. The interpretation of results obtained by combination of the two techniques confirm that low-field microwave phenomena are associated with the low-field magnetization processes observed at low-frequency, which are determined by the particular magnetic anisotropy present in the microwires. This conclusion is similar to giant magnetoimpedance phenomena typically observed at lower frequency range. Results are also discussed in terms of the suitability to extend the working frequency to employ these microwires as sensing elements up to the gigahertz range.