Frustration and microstructure : an example in magnetostriction

Microstructural properties of materials, especially crystalline solids, are implicated in many of their properties. Vice versa, there are macroscopic environments which limit microstructural configurations. Certain iron/rare earth alloys, eg, TbDyFe2, display both a huge magnetostriction and frustration, i.e., minimum energy not achieved, in which microstructure plays an important, if puzzling, role. We discuss this example in the framework of continuum thermoelasticity theory, where symmetry demands energy densities which are highly degenerate. This leads to novel analytical and computational issues, many of which we have been unable to resolve.