Ferroelasticity

The recently recognized property of ferroelasticity is far from uncommon and may have major physical implications. A crystal is ferroelastic if it has two or more stable orientational states in the absence of mechanical stress or electric field, and if it can be reproducibly transformed from one to another of these states by the application of mechanical stress. Ferroelasticity is a structure-dependent property and is directly inferable from the crystal structure. The onset of ferroelasticity, as a function of temperature or pressure, is often accompanied by additional cooperative phenomena. The strong interactive coupling expected of such multiproperty transitions opens a new and promising field. Examples of simple ferroelastics, ferroelastic-ferroelectrics, ferroelastic-ordered magnetics, and ferroelastic-superconductors are discussed in illustration of the principles of ferroelasticity.