Domain wall mobility in rare earth-transition metal alloys

The domain-wall mobility of amorphous alloys of rare-earth-transition-metal thin films has been measured at high temperatures (50 to 200°C) by means of the dynamic bubble collapse method for TbCo, GdCo, GdTbCo, TbFeCo, GdTbFe, and GdTbFeCo. It is found that the domain-wall velocity is linearly proportional to the applied field if the field is significantly larger than the coercivity. The values of the mobilities range from 0.9 to 29 cm/s-Oe. The mobility increases slightly with temperature in the range of 50-200°C. These data are in agreement with the fact that mobility is linearly related to the domain-wall width, which in turn increases in this temperature range because of the rapidly decreasing anisotropy. It is also found that mobility depends on the composition. Increasing the ratio of Gd to Tb significantly raises the value of the mobility