Effect of 1.5 MeV Proton Irradiation on Superconductivity in FeSe0.5Te0.5 Thin Films

Toshinori Ozaki,Itsuhiro Kakeya,Takuya Kashihara,Ryoya Ishigami

doi:10.3390/qubs5020018

Abstract

Raising the critical current density Jc in magnetic fields is crucial to applications such as rotation machines, generators for wind turbines and magnet use in medical imaging machines. The increase in Jc has been achieved by introducing structural defects including precipitates and vacancies. Recently, a low-energy ion irradiation has been revisited as a practically feasible approach to create nanoscale defects, resulting in an increase in Jc in magnetic fields. In this paper, we report the effect of proton irradiation with 1.5 MeV on superconducting properties of iron–chalcogenide FeSe0.5Te0.5 films through the transport and magnetization measurements. The 1.5 MeV proton irradiation with 1 × 1016 p/cm2 yields the highest Jc increase, approximately 30% at 5–10 K and below 1 T without any reduction in Tc. These results indicate that 1.5 MeV proton irradiations could be a practical tool to enhance the performance of iron-based superconducting tapes under magnetic fields.

Highlights

Iron-based superconductors have a reasonably high superconducting transition temperature Tc, very high upper critical magnetic fields Hc2, quite a small anisotropy γ and larger critical grain boundary angle than cuprate superconductors, which make them promising for high-field applications such as superconducting magnet and generators [1,2,3,4,5]
The use of superconducting materials for high field applications is limited by the critical current density Jc in magnetic fields, which can be sustained by pinning the vortices at structural defects with nano-meter sizes such as cracks, voids, grain boundaries and secondary phases [6,7]
Depending on the ion species, ion energy and the properties of the target materials, ion irradiation enables the creation of defects with well-controlled morphology and density, such as point [8], cluster [9,10,11,12] and columnar [13,14,15] defects

Summary

Introduction

Iron-based superconductors have a reasonably high superconducting transition temperature Tc, very high upper critical magnetic fields Hc2, quite a small anisotropy γ and larger critical grain boundary angle than cuprate superconductors, which make them promising for high-field applications such as superconducting magnet and generators [1,2,3,4,5]. We reported a route to raise both Tc and Jc in iron-based superconducting FeSe0.5Te0.5 (FST) thin films by low-energy (190 keV) proton irradiation [16,17].

Results

Conclusion