Evolution of the internal magnetic field in chalcogenide superconductors FeTe1−xSxFeTe1−xSx for various x values

• Non-zero internal magnetic fields are observed in Mössbauer spectra of FeTe1-xSx recorded between 6.8 K and 77 K with x = 0.05, 0.1 and 0.2.
• The temperature evolution and maximum value of the internal magnetic field was found to depend on the concentration of the sulphur atoms.
• Below the critical temperature of superconductivity the internal field decreases indicating that a competition between magnetism and superconductivity takes place.

The behavior of the internal magnetic field in FeTe1−xSxFeTe1−xSx was studied using Mössbauer spectroscopy in the temperature range from 6.8 K up to 300 K. Spectra of samples with x=0.05, 0.10 and 0.20 were recorded and the obtained hyperfine parameters were compared with the superconductivity properties. A dependence of the internal field on the x value and the superconductivity transition temperature was found.