Signatures for Berezinskii-Kosterlitz-Thouless critical behavior in the planar antiferromagnet BaNi2V2O8

We investigate the critical properties of the spin-1honeycomb antiferromagnet BaNi_2_2_8 both below and above the ordering temperature T_Nusing neutron diffraction and muon spin rotation measurements. Our results characterize BaNi_2_2_8as a two-dimensional (2D) antiferromagnet across the entire temperature range, displaying a series of crossovers from 2D Ising-like to 2D XY and then to 2D Heisenberg behavior with...