摘要
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.
原文 | English |
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頁(從 - 到) | 6496-6511 |
頁數 | 16 |
期刊 | Physical Review B - Condensed Matter and Materials Physics |
卷 | 62 |
發行號 | 10 |
DOIs | |
出版狀態 | Published - 2000 9月 1 |
All Science Journal Classification (ASJC) codes
- 電子、光磁材料
- 凝聚態物理學