Crystal structure and magnetic modulation in beta-Ce2O2FeSe2

We report a combination of X-ray and neutron diffraction studies, Mössbauer spectroscopy and muon spin relaxation (μ+SR) measurements to probe the structure and magnetic properties of the semiconducting β-Ce2O2FeSe2 oxychalcogenide. We report a new structural description in space group Pna21 which is consistent with diffraction data and second harmonic generation measurements and reveal an order-disorder transition on one Fe site at TOD ≈ 330 K. Susceptibility measurements, Mössbauer and μ+SR reveal antiferromagnetic ordering below TN = 86 K and more complex short range order above this temperature. 12 K neutron diffraction data reveal a modulated magnetic structure with q = 0.444 bN