On the nature and anisotropy of $Q \neq 0$ correlations in Tb_2Ti_2O_7 under the application of magnetic fields

TL;DR

This study investigates the magnetic field-induced ordered state in Tb2Ti2O7, revealing that it is dominated by non-zero wavevector correlations likely due to antiferromagnetism or lattice distortions, challenging previous spin-ice interpretations.

Contribution

The paper provides new neutron diffraction evidence showing that the ordered state in Tb2Ti2O7 under magnetic fields is characterized by Q ≠ 0 correlations, contrasting prior spin-ice-like models.

Findings

No re-entrant behaviour observed at high fields

Ordered state dominated by Q ≠ 0 correlations

Sensitivity to field alignment affects observed phenomena

Abstract

We report an analysis of neutron diffraction from single crystals of the spin-liquid pyrochlore Tb2Ti2O7 under the application of magnetic fields along the crystallographic $[110]$ direction. Such a perturbation has been shown to destroy the spin liquid ground state and induce long-range order, although the nature of the ordered state was not immediately determined. Recently, it has been proposed that the ordered state is characterized by spin-ice-like correlations, evincing an emergent ferromagnetic tendency in this material despite the large negative Curie-Weiss constant. Here, we argue instead that the ordered state is dominated by $Q \neq 0$ correlations that emerge either from strong antiferromagnetism or magnetoelastic distortion of the crystal. In contrast to previous reports, we observe no evidence for re-entrant behaviour in the high field limit. Extreme sensitivity of the ordered state to the alignment of the applied field is suggested to account for these discrepancies.