Figure 1. Superconducting transition and magnetization of the (Li _{1− x} Fe _x )OHFeSe crystal.

(a) Temperature dependence of resistivity of the sample. (b) Temperature dependence of DC magnetization measured with the zero-field-cooled (ZFC) and field-cooled (FC) modes at a field of 20 Oe. (c) The magnetization-hysteresis-loops measured at temperatures from 2 to 20 K. (d) Temperature dependence of the calculated critical current density J_s based on the Bean critical state model at zero magnetic field.