  By molecular dymanics simulations we study the spin Seebeck effect as a
function of magnetic field in the prototype classical easy-axis
antiferromagnetic chain, in the far-out of equilibrium as well as linear
response regime. We find distinct behavior in the low field antiferromagnetic,
middle field canted and high field ferromagnetic phase. In particular, in the
open boundary system at low temperatures, we observe a divergence of the spin
current in the spin-flop transition between the antiferromagnetic and canted
phase, accompanied by a change of sign in the generated spin current by the
temperture gradient. These results are corroborated by a simple spin-wave
phenomenological analysis and simulations in the linear response regime. They
shed light on the spin current sign change observed in experiments in bulk
antiferromagnetic materials.
