Transit-time measurements of domain-wall mobilities in YFeO3

Using a transit-time technique, we have measured domain-wall velocities versus applied field H for Bloch, Nêel, and the head-to-head walls in bulk single-crystal bars of yttrium orthoferrite from 150 to 600 °K. Fields as high as 100 Oe were applied and wall velocities exceeding 106 cm/sec were recorded. After correcting for magnetostatic effects, all three walls display a well-defined linear v-H region, with a common mobility μ of 1.2×104 cm/sec Oe at 300 °K. As a function of temperature T the wall mobility varies as 1/T2. From these results it is argued that the mobility arises from thermal spin-wave scattering. Velocities for the three walls become field independent abruptly at vs=4.2×105 cm/sec and maintain this velocity until H exceeds ∼60 Oe, whereupon the velocity again increases. We demonstrate that this ’’saturation’’ at vs is due to the interaction between the wall and the bulk acoustic phonons.