SEARCH CRITERION FOR LATTICE INTERNAL REARRANGEMENT MODES - CORRELATION BETWEEN LATTICE STRUCTURAL AND MAGNETIC STRUCTURAL TRANSITIONS

The occurrence of lattice internal rearrangements is of great interest because of the association through strong magnetoelastic interaction with first-order magnetic transitions, where the magnetic structure is likely to be unusual and highly anisotropic. We consider the physical basis for such modes occurring. The predictions for the NaCl and fluorite structures are quite restrictive on wave vector and polarization; and for the NaCl structure are highly evocative of a correlation between a lattice structural transition involving the predicted internal rearrangement mode and the magnetic transition to the IA magnetic structure. © 1978 The American Physical Society.