Domain wall bowing in a FeSi picture frame crystal measured by time-dependent neutron depolarization

A new technique is presented to study the shape of a moving domain wall within the volume of a ferromagnetic material, which is based upon time-dependent neutron polarization analysis (3×3 components). A polarized neutron beam passes through the long leg of a single crystal picture frame specimen of 3.5% silicon-iron. A single domain wall travels through the crystal by applying a small block shaped magnetic field on the leg. The polarization of the transmitted neutrons has been analyzed as a function of time. From the measured components increasing wall bowing up to 15 percent has been observed with magnetic fields up to 15 A/m. Beyond that value irregularities due to domain wall breaking have been observed in qualitative agreement with publications by Carr and Bishop. Together with the wall break a relative magnetization reduction of 4.10^-3has been observed, which has been attributed to persistent reversed magnetization regions.