Order by distortion and string modes in pyrochlore antiferromagnets

An attempt was made to demonstrate that a large spin degeneracy and high symmetry of the pyrochlore network provide a robust way to relieve spin frustration: by means of a Jahn-Teller distortion of tetrahedra. The theory has direct relevance to the observed magnetic and structural phase transitions and local modes in pyrochlore antiferromagnets YMn₂, ZnV₂O₄, MgV₂O₄, ZnCr₂O₄, and MgCr₂O₄.