  In this paper we consider a recent experiment [Kang et al. PRA 95 053638
(2017)] in which an antiferromagnetic spin-1 condensate of 23Na atoms was
quenched from the easy-axis polar phase into the easy-plane polar phase. We
simulate the phase transition dynamics using a classical field method with
noisy initial conditions and find good agreement to the experimental
observations. We analyse the late-time dynamics in terms of phase ordering
using the nematic order parameter that we have developed in earlier work [Symes
et al. PRA 96, 013602 (2017)]. We show that these experiments are able to
explore the early stages of universal phase ordering where the domains grow
diffusively.
