Phase separation and magnetic order in the Tl0.75K0.25Fe1.86Se2 superconductor studied by Mössbauer spectroscopy

► We provide experimental evidence for phase separation in the Tl0.75K0.25Fe1.86Se2 superconductor. ► We provide the first direct evidence for a two-magnetic moment antiferromagnetic structure of the magnetic phase. ► We determine the Debye temperature of the majority magnetic phase and the minority superconducting phase.