Abstract
We report neutron scattering measurements of the structural correlations associated with the apparent relaxor
transition in K1−xLixTaO3 for x = 0.02 [KLT(0.02)]. This compound displays a broad and frequency-dependent
peak in the dielectric permittivity, which is the accepted hallmark of all relaxors. However, no evidence of elastic
diffuse scattering or any soft-mode anomaly is observed in KLT(0.02) [J. Wen, et al., Phys. Rev. B 78, 144202
(2008)], a situation that diverges from that in other relaxors such as PbMg1/3Nb2/3O3.We resolve this dichotomy
by showing that the structural correlations associated with the transition in KLT(0.02) are purely dynamic at all
temperatures, having a time scale on the order of ∼ THz. These fluctuations are overdamped, nonpropagating,
and spatially uncorrelated. Identical measurements made on pure KTaO3 show that they are absent (within
experimental error) in the undoped parent material. They exhibit a temperature dependence that correlates well
with the dielectric response, which suggests that they are associated with local ferroelectric regions induced
by the Li+ doping. The ferroelectric transition that is induced by the introduction of Li+ cations is therefore
characterized by quasistatic fluctuations, which represents a stark contrast to the soft-harmonic-mode-driven
transition observed in conventional perovskite ferroelectrics such as PbTiO3. The dynamic, glasslike structural
correlations in KLT(0.02) are much faster than those measured in random-field-based lead-based relaxors, which
exhibit a frequency scale of order ∼ GHz and are comparatively better correlated spatially. Our results support
the view that random fields give rise to the relaxor phenomena, and that the glasslike dynamics observed here
characterize a nascent response.