Abstract
We have combined elastic and inelastic neutron scattering techniques, magnetic susceptibility, and resistivity
measurements to study single-crystal samples of KxFe2−ySe2, which contain the superconducting phase that has a
transition temperature of∼31 K. In the inelastic neutron scattering measurements, we observe both the spin-wave
excitations resulting from the block antiferromagnetic ordered phase and the resonance that is associated with
the superconductivity in the superconducting phase, demonstrating the coexistence of these two orders. From
the temperature dependence of the intensity of the magnetic Bragg peaks, we find that well before entering the
superconducting state, the development of the magnetic order is interrupted, at ∼42 K.We consider this result to
be evidence for the physical separation of the antiferromagnetic and superconducting phases; the suppression is
possibly due to the proximity effect of the superconducting fluctuations on the antiferromagnetic order.
