Magnetic phase transition and the spin excitations in cluster antiferromagnetic K0.8Fe1.6Se2

Abstract

We have studied the magnetic phase diagram and magnetic properties of iron selenide K0.8Fe1.6Se2 using an effective spin-exchange model. By applying the bond-operator approach, we show that the Fe moments form a checkerboard antiferromagnetic structure in a wide range of parameter regions, and the phase boundary between the magnetic phase and the spin-disordered phase is calculated as a function of the exchange interactions. We also calculate the spin excitation spectrums as well as the predicted inelastic neutron scattering patterns of the checkerboard antiferromagnetic state within the spin-wave method.