200 MeV Ag+15 ion irradiation created columnar defects and enhanced critical current density of La-2125 type superconducting thin films

TL;DR

This study demonstrates that 200 MeV Ag+15 ion irradiation creates columnar defects in La-2125 superconducting thin films, significantly enhancing their critical current density through improved flux pinning, with potential for practical applications.

Contribution

It is the first to show that high-energy ion irradiation induces columnar defects in La-2125 films, boosting their critical current density and stability compared to traditional RE-123 superconductors.

Findings

Critical current density increased fivefold at optimal irradiation levels.

Columnar defects were confirmed along the entire film thickness.

Enhanced Jc(H) is comparable to irradiated RE-123 superconductors.

Abstract

We have deposited c-axis oriented thin films of La1.5Dy0.5CaBa2Cu5Oz (La-2125) tetragonal superconductor on LaAlO3 (001) by Pulsed Laser Deposition. These films were irradiated with 200 MeV Ag+15 ions. Atomic Force Microscopy and Elastic Recoil Detection Analysis indicate that the irradiation has created columnar defects along the entire thickness (2000 A) of these films. With ion irradiation up to 1*10^11 ions/cm2, the critical current density (Jc(H)) is found to enhance by almost five folds, which is attributed to the augmented flux pinning by the columnar defects. A further increase in irradiation to 1*10^12 ions/cm2 causes reduction in Jc(H) due to distorted morphology of the film. Our work shows that the enhancement in Jc (H) of the irradiated La-2125 film is comparable to that in irradiated RE-123. Also, as the La-2125 type films have greater chemical stability than RE-123 (RE = rare earth ion), La-2125 type superconductors are potential candidates for applications. Interesting to note that there are partial flux jumps observed to occur symmetrically in the magnetic hysteresis of irradiated La-2125 thin films with enhanced Jc(H).