Microscopic considerations for models of ferromagnetic shape memory actuation

摘要

Micromagnetic and analytic models have been used to describe the equilibrium twin structure and quasistatic actuation behavior of ferromagnetic shape memory alloys. However, these models do not incorporate microscopic aspects of the twin-boundary strain field, interactions with defects or non-equilibrium (time-dependent) behavior. A model is described that accounts for the interaction of a 90° domain wall with such a twin boundary. Application of a magnetic field can displace the domain wall from a pinned twin boundary with the Zeeman energy being stored elastically in the domain-wall anisotropy energy. Finally, the departure of the magnetization and twin structure from equilibrium configurations can be incorporated in thermodynamic models to describe AC behavior and hysteresis.