MAGNETIC SOLITON MOTION IN A NONUNIFORM MAGNETIC-FIELD

We discuss the dynamics of a magnetic soliton in a one-dimensional fer romagnet placed in a weakly nonuniform magnetic held. In the presence of a constant weak magnetic-field gradient the soliton quasimomentum i s a linear function of time, which induces oscillatory motion of the s oliton with a frequency determined by the magnetic-held gradient; the phenomenon is similar to Bloch oscillations of an electron in a weak e lectric held. An explicit description of soliton oscillations in the p resence of a weak magnetic-field gradient is given in the adiabatic ap proximation. Two turning points are found in the motion of the soliton and the varieties of bounded and unbounded soliton motion are discuss ed. The Landau-Lifshitz equations are solved numerically for the case of a soliton moving in a weakly nonuniform magnetic field. The soliton is shown to emit a low-intensity spin wave near one of the turning po ints due to violation of the adiabatic approximation, and the necessar y conditions for such an approximation to hold are established. (C) 19 98 American Institute of Physics. [S1063-7761(98)02808-X].