Mobility and/or damping of the domain wall

The domain wall mobility of ferrimagnets is determined by using an original permeability spectrometer, which operates over a very broad frequency range (1 Hz to 1 GHz) from 77 to 600 K. Using such spectrometer permits to separate the diffusion relaxation and the domain wall relaxation. Three series of samples are investigated (YIG and Ni-Zn ferrites with various contents of diffusants and Gd-Y mixed garnets) in order to test the present theories of the domain wall damping: the diffusion damping theory and the spin damping theory. In fact, neither the diffusion damping nor the spin damping can account for the experimental mobility values. (author)