Domain-Wall Mobility in Yttrium Orthoferrite

Domain-wall mobility values from 6000 cm ${\sec }^{-1\mathrm{}}$ ${\mathrm{Oe}}^{-1\mathrm{}}$ at 300°K to 50 000 cm ${\sec }^{-1\mathrm{}}$ ${\mathrm{Oe}}^{-1\mathrm{}}$ at 77°K, among the highest observed in insulating magnetic materials, have been measured in YFe${\mathrm{O}}_3$. We have observed a monotonic temperature dependence of mobility which is qualitatively different from that found in other magnetic insulators and which we believe represents intrinsic behavior of wall mobility in YFe${\mathrm{O}}_3$. Domination of wall relaxation by surface roughness has been eliminated by proper surface preparation.