Spin-induced ferroelastics with pyrochlore lattices

Abstract

Spin ordering in the geometrically frustrated magnetic materials with pyrochlore lattices is a key player in the emergent phenomena in modern condensed matter. A possible spin-ordered phases derived from the archetypical pyrochlore lattice were studied within the Landau conception of order parameter (OP) for case wavevector k = (0,0,0) associated with the center of the Brillouin zone of space group $Fd\overline{3}m.$ The existence of 20 low-symmetry types of spin-ordered phases is established. For each phase space group and set of proper and improper OPs are defined. Only one phase generated by irrep mГ₂⁺ is not ferroelastic. The fundamental feature of spin-ordered phases in the pyrochlore lattices is that all remaining 19 phases found are improper ferroelastics. The Г₅⁺ (a,a,a) shear deformation, involved in the formation of phases with space groups $R\overline{3}m\prime ,$ $R\overline{3}{m}^{\prime },$ and $R\overline{3},$ is proved to be the only one that contributes to the formation of these rhombohedral distorted spin-ordered phases. Other types of shear deformations Г₅⁺(a,0,0) and Г₅⁺(a,b,b) are always cooperate with some of the Г₃⁺ deformations at the formation of spin-ordered pyrochlores.

Keywords:

• Pyrochlore lattice
• spin-ordered phases
• order parameter
• group-theoretical analysis
• improper ferroelastics

Additional information

Funding

The reported study was funded by Russian Science Foundation (RSF)–research projects no.22-22- 00183.