Supersonic domain-wall dynamics is investigated in wafer samples of YF
eO3 having thicknesses of 10 mu m, 35 mu m, 40 mu m, 120 mu m, and 125
mu m, prepared by different methods, and in a mm, mm, EuFeO3 sample o
f thickness 60 mu m at liquid-nitrogen temperature. Relations are esta
blished for the occurrence of nonlinear segments in the form of consta
nt-wall-velocity intervals in the dependence of the wall velocity on t
he pulsed magnetic field amplitude. Qualitative agreement is obtained
between the experimental data and calculated values of the velocities
and widths of the constant-velocity intervals, on the assumption that
the mechanism of resonance retardation of the domain walls by parametr
ically excited Winter (wall as opposed to bulk) magnons is operative a
t supersonic velocities. (C) 1998 American Institute of Physics. [S106
3-7834(98)01909-1].