An incremental theory of magneto-elastic hysteresis in pseudo-cubic ferro-magnetostrictive alloys

This paper presents an incremental hysteretic magneto-elastic constitutive theory of pseudo-cubic ferromagnetostrictive alloys, which may be used to predict the magneto-elastic response of these materials under quite general applied magnetic field and stress processes. These processes may include fully saturated major loop, unsaturated minor loop or more general types of magnetic field-stress processes. Comparisons between model results and a set of high quality measurements show that the model is capable of qualitative agreement with the experimental behavior. However, the experimental data shows a strongly decreasing magnetization and magnetostriction hysteresis as the minor loop cyclic applied field amplitude becomes smaller. It appears that irreversible domain wall motion continuously activates as the applied magnetic field is reduced in the range from 79 to 39 kA/m. Minor loop processes which do not have a sufficiently low minimum applied magnetic field value do not activate irreversible domain wall translation events and any measured magnetization changes must be due to one or more reversible mechanisms such as domain wall bowing and reversible domain rotation. The present model only includes an irreversible domain wall translation mechanism, therefore the model hysteresis widths remain constant with decreasing minor loop cyclic applied field amplitude. (C) 2002 Elsevier Science B.V. All rights reserved.