Resonant transmission of microwave radiation through iron-rich metal-metalloid foils at 9 GHz

Magnetic-field-dependent microwave transmissions have been observed to take place across the thickness of iron-rich metal-metalloid foils that are much thicker than the microwave skin depth at FMR (ferromagnetic resonance). The attenuation constants of these transmissions have been obtained from the dependence of the transmission intensity on the specimen thickness and have been found to depend little on the difference of such magnetic properties as magnetization, magnetostriction, and permeability. These attenuation constants are about four times smaller than those of the driving microwave field within the specimen, and the attenuation lengths estimated from these attenuation constants are about 4.5 μm. The observations are not consistent with the possibility that a direct penetration of the driving microwave field is responsible for the present transmission phenomenon. The effect of evaporated nickel-iron films on the transmission peak has been examined in the thickness range from 1000 Å to 6000 Å. It has been found that the transmission peak changes nonmonotonically depending on the film thickness. This nonmonotonic change indicates that there is a kind of interference effect due to waves of submicron wavelengths. The results are consistent with the possibility that the observed magnetic-field-dependent microwave transmissions are caused by elastic or magnetoelastic waves