| תקציר: | Superconducting stiffness and coherence length are commonly determined from the penetration depth and the upper critical field, respectively. In iron-based superconductors, however, the internal magnetic fields can substantially deviate from the applied field due to exchange field, leading to inaccurate estimates of both quantities. To address this problem in Fe_{1+y}Se_{x}Te_{1-x} (x=0.5, y=0), we employed the Stiffnessometer technique. In this method, a rotor-free vector potential ($A$) is applied to a superconducting ring, and the resulting current density is extracted from its magnetic moment. Using London’s relation and the Ginzburg-Landau framework, we directly determine both superconducting stiffness and coherence length. Our stiffness measurements reveal the presence of two superconducting gaps, with temperature dependence deviating from the conventional BCS two-gap s-wave pairing model. We also employed standard magnetization measurements under an applied magnetic field, and investigated time-dependent magnetization in both Fe_{y}Se_{0.5}Te_{0.5} and a Nb_{0.61}Ti_{0.27}N_{0.11} of similar geometry, identifying it's origin as a geometric effect intrinsic to thin superconducting rings. |