The behaviour of ferromagnetic domains in silicon iron under stress

Polycrystalline and single crystal specimens of silicon iron were strained up to the yield point by the application of external stresses. A tending technique was found to be the most convenient method for doing this. Domain patterns were observed by means of the Bitter technique. Tensional stresses were applied along the [110] and 001] directions of (110) surfaced specimens and the result ing structures described in detail. This necessitated an analysis of the effect of stress on Bloch Wall energies for various wall orientations. Domain patterns were also examined on (100) surfaced specimens under the effect of compressive forces in the [110] and [100] directions. In the first case the maze patterns so produced were compared with theoretical considerations while in the second example the nucleation and growth of transverse domains were examined. A new model of fir tree structures, proposed by Spacek, was evaluated using a different expression for the magnetostatic energy and this was then applied to measurements on the effect of stress on fir tree closure domains. The theory did not compare very favourably with experiment. The work of Chikazumi and Suzulci, in which large stresses were applied to a (l00) surfaced specimen by scratching the surface, was extended to (110) surfaces.