Superconducting Phase Transitions and Flux Pinning Configurations in Niobium-Zirconium Thin Films

International Journal of Physics | Vol. 13, No. 7, July 2022 | pp. 49–56

DOI: 10.46882/2022/IJP/000147

Research Article

Title: Superconducting Phase Transitions and Flux Pinning Configurations in Niobium-Zirconium Thin Films

Names of Authors: O. K. Semenov¹, Y. S. Kim²

Authors’ Affiliations:
¹ Institute for Solid State Physics, Russian Academy of Sciences, Moscow, Russia
² Department of Physics and Astronomy, Seoul National University, Seoul, South Korea

Abstract: Enhancing the critical current density of superconducting alloys under strong magnetic fields is a crucial requirement for next-generation quantum computing circuits, single-photon detectors, and fusion magnet components. This study evaluates the superconducting phase transitions and maps magnetic flux pinning configurations in niobium-zirconium (Nb-Zr) thin films. The thin films were prepared via co-sputtering on sapphire substrates with film thicknesses ranging from 50.0 nm to 300.0 nm. We conducted low-temperature electrical transport and magnetometry measurements across a temperature range of 1.5 K to 12.0 K under magnetic fields up to 8.0 T. The pristine 300.0 nm film displayed a sharp superconducting transition with a critical temperature (Tc) of 10.8 K at zero field. Magnetization loops revealed a high critical current density (Jc) exceeding 3.8 x 10^6 A/cm² at 4.2 K. Analysis of the pinning force density indicates that the dominant pinning mechanism shifts from core-surface pinning to point-defect pinning as the temperature approaches Tc. The upper critical field, Hc2(0), was estimated to be 12.4 T by applying the Werthamer-Helfand-Hohenberg theoretical model. These findings demonstrate that nanoscale structural control significantly improves vortex lattice stability under magnetic stress.

Keywords: Superconductivity; thin films; flux pinning; critical current density; upper critical field; magnetron sputtering

Manuscript Timeline: Received: April 05, 2022; Revised: June 01, 2022; Accepted: June 28, 2022; Published: July 15, 2022

Citation: Semenov, O. K., & Kim, Y. S. (2022). Superconducting Phase Transitions and Flux Pinning Configurations in Niobium-Zirconium Thin Films. International Journal of Physics, 13(7), 49–56.

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