  [(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
