Multi-band superconductivity and large anisotropy in FeS crystals

By using a hydrothermal method, we have successfully grown crystals of the newly discovered superconductor FeS, which has an isostructure of the iron based superconductor FeSe. The superconductivity appears at about 4.5K, as revealed by both resistive and magnetization measurements. It is found that the upper critical field is relatively low, with however an rather large anisotropy $\Gamma=[(dH_{c2}^{ab}/dT)/(dH_{c2}^{c}/dT)]_{T_c}\approx5.8$. A huge magnetoresistivity (290$\%$ at 9T and 10K, ${H}$ $\parallel$ c-axis) together with a non-linear behavior of Hall resistivity vs. external field are observed. A two-band model is applied to fit the magnetoresistance and non-linear transverse resistivity, yielding the basic parameters of the electron and hole bands.