Dynamics of magnetic domain walls in an oscillating field

The dynamics of domain walls in an ac magnetic field is formulated and solv ed numerically under free boundary conditions. Previous calculations are ap plicable only in the limit when the sample size is much less than the bare penetration depth, whereas no such approximation is made in the present app roach. Our calculation provides for an interpretation of recent experimenta l results that observe a peak in the ac susceptibility of soft magnets as a function of the amplitude of the external magnetic field. (C) 2000 America n Institute of Physics. [S0021-8979(00)28908-1].