AC multi-harmonic susceptibility measurements were performed in the FeSe0.25Te0.75 superconductor. A large frequency-magnetic field-temperature (f-H-T) region of the superconducting phase diagram was mapped under a wide range of the DC magnetic field. In particular the irreversibility line was accurately drawn up to 20 T as a function of both T and f. The frequency dependence of the irreversibility line was analyzed using the 3D vortex glass model, well describing the experimental behavior up to high magnetic field. The data evidence the evolution in time of the metastable critical state in a final stable vortex glass phase by decreasing the frequency. Moreover, from the Werthamer, Helfand and Hohenberg theory we estimated the upper critical field μ0Hc2 (0 K)∼ 62 T. The observed 3D flux-pinning response points out that this system is suitable for carrying quite high critical currents.
Puri, A., Marcelli, A., Poccia, N., Ricci, A., Zeitler, U., & Di Gioacchino, D. (2015). Vortex dynamics and irreversibility line in FeSe0.25Te0.75. In Physics Procedia (Vol. 67, pp. 890–895). Elsevier B.V. https://doi.org/10.1016/j.phpro.2015.06.150