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Zusammenfassung

The paper presents Mossbauer spectroscopy investigation on superconducting Rb Fe-0.8 Se-1.6 (2) exhibiting nanoscale phase separation and two its derivatives: Cu-doped Rb Fe-0.8 Cu-1.56 Se-0.04 (2) and Fe-deficient Rb Fe-0.7 Se-1.4 (2). The spectra reveal the presence of the same dominant magnetic sextet in the samples, which is assigned to the Fe 16i sites of the ae5xae5x1 superstructure. This magnetic part is independent on the modification of the sample and does not undergo any changes after doping or deviation of stoichiometry. In contrast, the minor non-magnetic doublet in the spectra of Rb Fe-0.8 Se-1.6 (2), which is attributed to the superconducting nanoscale phase, is sensitive to such modifications. After doping with Cu, the relative intensity of non-magnetic doublet significantly decreases together with suppression of superconductivity. On the other hand, the Fe-deficient sample is entirely magnetically ordered below 250 K including in the minor nanoscale phase. A discussion of Mossbauer spectroscopic data and comparison with previous studies on other Fe chalcogenide analogues allow to conclude the nanosized phase separation is also observed in non-stoichiometric and doped modifications of Rb Fe-0.8 Se-1.6 (2).