Neutron and X-Ray Scattering Studies of Premartensitic Phenomena

Abstract

Competing interactions play an essential role in all types of phase transitions. In the much studied spin glasses it is well known that the competing ferro- and antiferromagnetic interactions lead to a spin’s frustration resulting in the frozen spin glass state at low temperatures /1/. In ferroelectrics, the competition is between short-range interatomic forces and longer range electric dipolar forces which leads to the structural instability associated with ferroelectric ordering /2/. In metals, where martensitic phase transitions occur, the competing forces are not as well defined, but are likely due to the interatomic forces and the longer range electronic interactions. Depending upon the electronic band structure and the phonon dispersion curves of the solid, a variety of structures and microstructures can appear over a wide range of temperatures and compositions.