Magnetic order and spin dynamics in La2 O2 Fe2 OSe2 probed by Fe 57 Mössbauer, la 139 NMR, and muon-spin relaxation spectroscopy

We present a detailed local probe study of the magnetic order in the oxychalcogenide La2O2Fe2OSe2 utilizing Fe57 Mössbauer, La139 NMR, and muon-spin relaxation spectroscopy. This system can be regarded as an insulating reference system of the Fe arsenide and chalcogenide superconductors. From the combination of the local probe techniques we identify a noncollinear magnetic structure similar to Sr2F2Fe2OS2. The analysis of the magnetic order parameter yields an ordering temperature TN=90.1K and a critical exponent of β=0.133, which is close to the two-dimensional Ising universality class as reported in the related oxychalcogenide family.