On the nature of the microwave spectra and relaxation in conductive Fe4+-doped garnet films

The origin of the large magnetic relaxation effects at microwave frequencies observed in Fe
⁴⁺
-doped YIG films has been investigated in detail. Owing to the fairly high conductivity, eddy currents play a fundamental role in shaping the microwave spectra, leading to a superposition between a narrow magnetostatic mode series and a broad background signal. At the same time, eddy currents provide the largest contribution to the magnetic damping, giving rise to a characteristic linewidth angular dependence. Experimental results are in agreement with a simple model developed by means of a magnetostatic approach.