Hysteresis of Néel-line motion and effective width of 180 degrees Bloch walls in bulk iron.

Subdivided 180\ifmmode^\circ\else\textdegree\fi{} Bloch walls of alternating polarity have been observed on iron whiskers employing the interference-contrast colloid technique. The field-induced conversion of these complex walls is predominantly controlled by N\'eel-line motion. The static polarization curves, optically recorded for whiskers of various thicknesses, permit an experimental estimation of an effective Bloch-wall width which is in good agreement with the theoretically obtained value for bulk material.