• Beek, Cornelis Jacominus Van Der
• Nouailhetas, Quentin
• Koblischka, Michael
• Berger, Kévin
• Douine, Bruno
• Koblischka-Veneva, Anjela

Abstract

Bulk, polycrystalline samples of FeSe are interesting candidates for trapped field applications as the material can be prepared by simple solid-state sintering, is free of toxic elements and exhibits magnetic properties like the copper-based high-Tc superconductors, i.e., high upper critical fields Hc2, and relatively small anisotropy. Polycrystalline, sintered FeSe material shows further promising features such as strong grain coupling. The FeSe material consists of well-coupled, but randomly oriented, platelet-like round grains with a diameter between 1 and 6 µm.However, the critical currents of the FeSe system are still low, but comparable to sintered MgB2. The goal of the present work is to explore the possibilities of the FeSe system in application-type samples (i.e., polycrystalline material, not single crystals) using electron irradiation. Pieces of bulk, superconducting FeSe samples prepared by solid-state sintering were irradiated with 2.5 MeV electrons (T = 23.5 K) at SIRIUS facility using two different fluences, 2×10^19 electrons/cm2 and 4×10^19 electrons/cm2. The electron irradiation introduced point defects to the FeSe grains. The changes of Tc due to irradiation and the critical currents were measured using SQUID magnetometry. As result, the superconducting transition temperature, Tc, is slightly reduced, depending on the fluence, but the critical currents are increased by about 20-30%, which demonstrates that one can introduce additional disorder to FeSe to improve the flux pinning properties also in the polycrystalline material.

Topics

• impedance spectroscopy
• single crystal
• grain
• copper
• sintering
• point defect