R. Zamorano

Correlations between low-field microwave absorption and magnetoimpedance in Co-based amorphous ribbons

Microwave power absorption measurements at 9.4 GHz were carried out on as-cast amorphous ribbons of nominal composition Co66Fe4B12Si13Nb4Cu. Two absorptions were observed: a small signal at a low dc field (<0.01T) and another one at a high dc field (∼0.1682T). The high-field signal shows all the features corresponding to ferromagnetic resonance. The low-field absorption (LFA) signal exhibits different characteristics such as hysteresis and a minimum in power absorption at zero magnetic field. A correlation between this LFA signal and magnetoimpedance measurements showed that both electromagnetic processes are associated with the same phenomenon.

Effect of the Particle Size on the Microwave Absorption in the Yttrium-Iron Garnet

A comparative study between micropowders and nanopowders of Y3Fe5O12 (YIG) by means of ferromagnetic resonance (FMR) is reported. Significant changes in lineshape of the FMR spectra between both samples are observed, in particular, the absorption mode in nanopowders have an internal structure which can be associated with magnetostatic modes. Additionally, a method to measure the non-resonant microwave absorption, as function of an applied magnetic field around zero field, known as the low-field microwave absorption (LFMA) is also employed. LFMA technique is used to give a further knowledge on the YIG samples, showing their main characteristics highlighted. These techniques are powerful tools for the research of magnetic materials at microwave frequencies.