Evidence for the interaction between magnetic domain walls and dislocations in high-purity iron from magnetomechanical damping experiments

The magnetomechanical damping, when plotted as a function of the amplitude of an alternative shear strain, exhibits a maximum, from which it is possible to deduce the effective internal stress opposed to the motion of 90° magnetic domain walls. High-purity specimens of iron are strained up to 3% at room temperature, and from the variation of internal strain with applied stress it is shown that the effective internal stress is proportional to the square root of dislocation density. During further straining at 77K, the interaction between 90° magnetic domain walls and dislocation tangles is evidenced: the dislocation density inside the tangles decreases together with the effective internal stress, while the mobility of magnetic domain walls increases. The dislocation density inside the tangles is calculated for the sample prestrained 3% at room temperature from the values of the effective internal stress.