Highfrequency properties of amorphous microwires

Microwave engineering is of great importance in a wide spectrum of applications most of them related to wireless telecommunications systems, as in telephone, broadcast satellite television, or in satellite global positioning. Recently the demand for high density integration of electronic devices has lead to serious noise and signal interference problems, promoting the research and development of thin films with specific features of electromagnetic noise absorption. As this research is evolving, a need to control the magnetic anisotropy and resistivity for thin films came into attention since near field absorption is tailored by ferromagnetic resonance profile and eddy current losses. On the other hand it has been widely documented that amorphous microwires possess very interesting high frequency properties due to the strong magnetoelastic anisotropy which is induced in the fabrication process. By defining strictly the geometric characteristics and the alloy composition the ferromagnetic resonance profiles can be accurately controlled. Furthermore, the high production rate and high permeability feature of microwires without any rigid substrates are advantageous for use as noise absorbers. The discovery of natural ferromagnetic resonance (NFMR) in amorphous microwires was preceded by their study with standard FMR method.