We have determined the superconducting and magnetic properties of a hydrothermally synthesized powder sample of tetragonal FeS using muon spin rotation ($\mu \mathrm{SR})$. The superconducting properties are entirely consistent with those of a recently published study, showing fully gapped behavior and giving a penetration depth of ${\lambda }_{ab}=204\left(3\right)$ nm. However, our zero-field $\mu \mathrm{SR}$ data are rather different and indicate the presence of a small, nonsuperconducting magnetic phase within the sample. These results highlight that sample-to-sample variations in magnetism can arise in hydrothermally prepared phases, but interestingly the superconducting behavior is remarkably insensitive to these variations.

• Received 4 July 2016
• Revised 8 September 2016

DOI:https://doi.org/10.1103/PhysRevB.94.134509