title: Coexistence of 3d-ferromagnetism and superconductivity in [(Li1-x Fex )OH](Fe1-y Liy )Se.
abstract: Superconducting [(Li1-x Fex )OH](Fe1-y Liy )Se (x≈0.2, y≈0.08) was synthesized by hydrothermal methods and characterized by single-crystal and powder X-ray diffraction. The structure contains alternating layers of anti-PbO type (Fe1-y Liy )Se and (Li1-x Fex )OH. Electrical resistivity and magnetic susceptibility measurements reveal superconductivity at 43 K. An anomaly in the diamagnetic shielding indicates ferromagnetic ordering near 10 K while superconductivity is retained. The ferromagnetism is from the iron atoms in the (Li1-x Fex )OH layer. Isothermal magnetization measurements confirm the superposition of ferromagnetic and superconducting hysteresis. The internal ferromagnetic field is larger than the lower, but smaller than the upper critical field of the superconductor. The formation of a spontaneous vortex phase where both orders coexist is supported by (57) Fe-Mössbauer spectra, (7) Li-NMR spectra, and μSR experiments.
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus D), 81377 München (Germany).
authors.forename: Ursula
authors.initials: U
authors.lastname: Pachmayr
authors.forename: Fabian
authors.initials: F
authors.lastname: Nitsche
authors.forename: Hubertus
authors.initials: H
authors.lastname: Luetkens
authors.forename: Sirko
authors.initials: S
authors.lastname: Kamusella
authors.forename: Felix
authors.initials: F
authors.lastname: Brückner
authors.forename: Rajib
authors.initials: R
authors.lastname: Sarkar
authors.forename: Hans-Henning
authors.initials: HH
authors.lastname: Klauss
authors.forename: Dirk
authors.initials: D
authors.lastname: Johrendt
keywords: ferromagnetism; iron selenides; structure elucidations; superconductivity