Spin dynamics in highly frustrated pyrochlore magnets
1 Laboratoire Léon Brillouin, CEA Saclay, 91190 Gif-sur-Yvette, France
2 SPEC, CEA Saclay, 91190 Gif-sur-Yvette, France
3 ICMMO, Université Paris XI, 91405 Orsay, France
4 Institut Laue Langevin, 6 rue Jules Horowitz, BP. 156, 38042 Grenoble, France
a e-mail: email@example.com
Published online: 23 January 2015
This paper aims at showing the complementarity between time-of-flight and triple-axis neutron scattering experiments, on the basis of two topical examples in the field of geometrical magnetic frustration. Rare earth pyrochlore magnets R2Ti2O7 (R is a rare earth) play a prominent role in this field, as they form model systems showing a rich variety of ground states, depending on the balance between dipolar, exchange interactions and crystal field. We first review the case of the XY antiferromagnet Er2 Ti2 O7. Here a transition towards a Néel state is observed, possibly induced by an order-by-disorder mechanism. Effective exchange parameters can be extracted from S(Q,ω). We then examine the case of the spin liquid Tb2 Ti2 O7. Recent experiments reveal a complex ground state characterized by “pinch points” and supporting a low energy excitation. These studies demonstrate the existence of a coupling between crystal field transitions and a transverse acoustic phonon mode.
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