Thermodynamic and single-ion properties of Tb3+ within the collective paramagnetic-spin liquid state of the frustrated pyrochlore antiferromagnet Tb2Ti2O7

M. J.P. Gingras, B. C. den Hertog, M. Faucher, J. S. Gardner, S. R. Dunsiger, L. J. Chang, B. D. Gaulin, N. P. Raju, J. E. Greedan

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Abstract

In a recent paper [J. S. Gardner et al., Phys. Rev. Lett. 82, 1012 (1999)] it was found that the Tb3+ magnetic moments in the Tb2Ti2O7 antiferromagnetic pyrochlore lattice of corner-sharing tetrahedra remain in a collective paramagnetic state down to 70 mK. In this paper we present results from dc magnetic susceptibility, specific-heat data, inelastic neutron-scattering measurements, and crystal-field calculations that strongly suggest that (i) the Tb3+ ions in Tb2Ti2O7 possess a moment of approximatively 5 μB, and (ii) the ground state g-tensor is extremely anisotropic below a temperature of O(100) K, with Ising-like Tb3+ magnetic moments confined to point along a local cubic 〈111〉 diagonal (e.g., towards the middle of the tetrahedron). Such a very large easy-axis Ising-like anisotropy along a 〈111〉 direction dramatically reduces the frustration otherwise present in a Heisenberg pyrochlore antiferromagnet. The results presented herein underpin the conceptual difficulty in understanding the microscopic mechanism(s) responsible for Tb2Ti2O7 failing to develop long-range order at a temperature of the order of the paramagnetic Curie-Weiss temperature θcw≅ - 101 K. We suggest that dipolar interactions and extra perturbative exchange coupling(s) beyond nearest neighbors may be responsible for the lack of ordering of Tb2Ti2O7.

Original languageEnglish
Pages (from-to)6496-6511
Number of pages16
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume62
Issue number10
DOIs
Publication statusPublished - 2000 Sep 1

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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