Spin flop in one-dimensional Heisenberg antiferromagnet KCuF₃

Following Yamada and Kato J. Phys. Soc. Japan 63 (1994) 289, we have calculated the frequency－field diagram of antiferromagnetic resonance of KCuF_3 using an eight-sublattice model and mean field approximation. A spin flop is found to take place from the 110_p to a direction perpendicular to 110_p in the c-plane at H\simeq 42172A/m, which is in good agreement with the data obtained by measuring magnetic susceptibility.