The magnetic excitations in the ground state of Yb₂Ti₂O₇

The nature of the zero-field ground state of Yb₂Ti₂O₇ remains an enigma within the pyrochlore titanate series. The disparate results are attributed to subtle changes in the sample stoichiometry, which seems to tune the delicate magnetic order of different samples across a phase boundary. We report a thorough study on the zero-field ground state of a powder sample of the pyrochlore Yb₂Ti₂O₇ [1]. A sharp, heat capacity anomaly at Tc =280 mK is accompanied by a quasi-collinear ferromagnetic order with a magnetic moment of 0.87(2)μ_B. Our high-resolution inelastic neutron scattering measurements show that, at 10 K, a broad quasielastic paramagnetic scattering dominates the observed energy range. Upon cooling, an inelastic continuum of excitations at ~0.6 meV is observed to persist from at least 2.5 K down to the lowest reached temperatures. Below Tc, the coexistence of sharp gapped low-energy magnetic excitations with a remnant quasielastic contribution evidences that spin fluctuations persist despite the long-range magnetic order.
[1] Viviane Peçanha-Antonio et al., arXiv:1709.01013