Fig. 1: Magnetic properties of a hybrid perovskite antiferromagnet.

a Schematic illustration of the acoustic and optical modes in a two-sublattice easy-plane antiferromagnet that are protected from interacting by parity. b A sketch of the inherently low symmetry of the Cu-EA structure due to octahedral tilting and the spin ordering of the layered antiferromagnet and its sublattice structure. c Magnetic properties of Cu-EA at T = 2.5 K. M(H) loops are obtained along all three principal axes of the single crystal up to saturation region. The upper inset shows the spin-flop transition at low field at \(\left|{{{{{{\bf{H}}}}}}}_{{{{{{\bf{ext}}}}}}}\right |=30\,{{{{{\rm{mT}}}}}}\). M vs. T is included in the lower inset to show the onset of magnetic ordering at the transition temperature, T ~ 10 K.