[(Li0.8Fe0.2)OH]FeS and the ferromagnetic superconductors   [(Li0.8Fe0.2)OH]Fe(S1-xSex) (0<x<1)
  [(Li0.8Fe0.2)OH]FeS and the series [(Li0.8Fe0.2)OH]Fe(S1-xSex) (0<x<1) were synthesized by hydrothermal methods and characterized by X-ray single crystal and powder diffraction, EDX and chemical analysis. Selenium-rich compounds show the coexistence of magnetic ordering with superconductivity known from the pure selenium compound. Sulphur doping decreases the critical temperature through chemical pressure until superconductivity is completely absent in [(Li0.8Fe0.2)OH]FeS, while the ferromagnetism in the [(Li0.8Fe0.2)OH] layers persists. The Li:Fe ratio in the hydroxide layer, and thus the charge transfer of 0.2 electrons from the hydroxide to the iron chalcogenide layers remains unchanged in [(Li0.8Fe0.2)OH]Fe(S1-xSex), which indicates that the chemical pressure effect of the smaller sulphide ions impedes superconductivity in [(Li0.8Fe0.2)OH]FeS 
Ursula Pachmayr and Dirk Johrendt
cond-mat.supr-con