DOMAIN-WALL DYNAMIC INSTABILITY

Computer simulation is utilized to follow the dynamic evolution of a one-dimensional Bloch domain wall. The Landau-Lifshitz equation with Gilbert damping is solved with the applied field along the domain magnetization. Walker's solution is verified for the case where the anisotropy field is much larger than the Walker critical field. When the critical field is comparable to the anisotropy field, the wall motion exhibits instability. For an external field lower than the Walker critical field, after some transient behavior, the steady-state Walker-type wall configuration is reached; when the applied field is above the Walker limit, the initial single wall gradually evolves into an odd number of Bloch walls with consecutively opposite senses. Wall motions for soft ferrite material with different dampings are also investigated. For very small damping the stability holds well. However, for medium damping, it is found that below some critical field, smaller than Walker's, the steady-state solution is stable. Above that field, the single wall first develops a frontal wake which enlarges until instability when an odd number of walls form.