The effect op stress on the domain structures of iron whiskers

Abstract

Large iron whiskers were grown by the reduction of ferrous chloride and domain structures In unstrained and strained whiskers were Investigated. Tensional stresses were applied along the whisker axis and the resulting domain patterns observed by means of the Bitter technique. In the, case of whiskers with axes in [l00] directions and faces (001) cross-magnetised domains were observed to disappear upon the application of stress, either by the gradual reduction of their volume or by the sudden mutual annihilation of neighbouring domains. Calculations of the energy values for these sudden changes agree with the model postulated and visual observation of the movement confirmed the theory. For whiskers with axes at an angle to the [100] direction and faces (00l), calculations were carried out upon a number of different closure structure types to determine the equilibrium spacing for each pattern and these were then compared with observations to confirm the type of closure structure present. A method of estimating magnetostatic energy contributions for areas of free pole separated by neutral regions was developed. Whiskers with axes [111] and faces (211) and (110) were also studied. Calculations showed that the main wall was a normal zig-zag wall. The main structure was observed to consist of six 90º domains and two different types of closure structure were observed on alternate main domains. The effect of stress on this structure was explained as being due to the change in energy of the complex wall structure in the two different closure structures.