Accueil du site Séminaires Seminaire Magnétisme frustré

Seminaire Magnétisme frustré

Jeudi 17 Avril à 14h00,
salle Remy Lemaire, K223

Orateur : Stephanie Curnoe (Memorial University, Canada)
"Symmetry and quantum mechanics on a frustrated lattice : rare earth pyrochlores"


The methods of finite group theory are a powerful means of reducing the complexity of highly symmetric crystals such as the rare-earth pyrochlores. In these materials, the rare-earth ions are located at the vertices of a network of corner-sharing tetrahedra, an arrangement known as "geometric frustration". The total angular momenta J of the rare earth ions are large, however, the 2J+1-fold degeneracy is lifted by the local environment of the crystal electric field (CEF) such that the ground states are doublets. Recently, there has been a great deal of effort to analyse the CEF doublets in pyrochlores as spin-1/2 doublets because it provides a description of real materials in terms of an ideal model of geometrically frustrated spin-1/2 particles interacting by the nearest-neighbour exchange interaction, and thus offers a point of comparison of various real materials. Symmetry (group theory) analysis will be used to derive an effective spin-1/2 nearest-neighbour exchange model for the pyrochlore Tb2Ti2O7.

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