Domain-wall mobility in some rare-earth iron garnets

The domain-wall mobility has been measured in (Gd
1-x
Tb
x
)
3
Fe
5
O
12
and (Gd
1-x
Dy
x
)
3
Fe
5
O
12
for
x
in the range 0 to 0.33. All the measurements were performed at 25°C on flux-grown crystals, and the mobility was found to vary from 2250 (cm/s)/Oe for Gd
3
Fe
5
O
12
to 160 (cm/s)/Oe for (Gd
0.67
Dy
0.33
)
3
Fe
5
O
12
and 78 (cm/s)/Oe for (Gd
0.67
Tb
0.33
)
3
Fe
5
O
12
. The damping of the wall motion was found to increase linearly with
x
to a good approximation. A method of determining the wall mobility in bulk samples from measurements of the RF susceptibility spectra is described. The results are discussed in terms of the slow relaxation model.