H. Montiel

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.

Magnetization dynamics and ferromagnetic resonance behavior of melt spun FeBSiGe amorphous alloys

Frequency-dependent magnetic properties of melt spun Fe80B10Si10-xGex (x = 0.0–10.0) were studied by means of inductance spectroscopy (using the complex permeability formalism) and ferromagnetic resonance techniques. The magnetization dynamics showed two magnetization mechanisms, reversible bulging of domains and hysteresis. The dominant mechanism changed as Ge progressively replaced Si; the changes reflect the crystallization processes observed for higher Ge contents, x > 5. High relaxation frequencies (above 1 MHz) were observed for alloys with x ≥ 2.5. In the ferromagnetic resonance response, coupling and decoupling between the amorphous and crystalline phases were detected depending on the orientation of the alloy samples. This allowed the calculation of the anisotropy fields of the alloys—the decreasing trend with increasing Ge content was interpreted in terms of a variable easy direction.

Resonant and nonresonant phenomena in measurements of ferromagnetic resonance in Co/sub 66/Fe/sub 4/B/sub 12/Si/sub 13/Nb/sub 4/Cu/sub 1/ amorphous ribbons

Ferromagnetic resonance measurements were carried out on amorphous ribbons of composition Co/sub 66/Fe/sub 4/B/sub 12/Si/sub 13/Nb/sub 4/Cu/sub 1/ prepared by melt spinning. The field modulated power absorption (dP/dH) was measured as a function of DC magnetic field (H) on strips 2 mm long, in an Electron Paramagnetic Resonance (EPR) spectrometer at X band (9.4 GHz) and Q Band (35 GHz). All spectra were taken at room temperature, under DC magnetic fields up to 10 KG for band X and 20 KG for band Q.