Superconducting Phase Transitions and Magnetic Flux Pinning Mechanisms in Niobium-Titanium Thin Films

International Journal of Physics | Vol. 5, No. 11, November 2014 | pp. 81–88

DOI: 10.46882/2014/IJP/000055

Research Article

Title: Superconducting Phase Transitions and Magnetic Flux Pinning Mechanisms in Niobium-Titanium Thin Films

Names of Authors: O. K. Semenov¹, A. L. Vance²

Authors’ Affiliations: ¹Institute for Solid State Physics, Russian Academy of Sciences, Moscow, Russia; ²Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK

Abstract: Enhancing the current-carrying capability of superconductors under strong magnetic fields is a critical requirement for next-generation particle accelerators and magnetic resonance imaging systems. This study evaluates the superconducting phase transitions and maps magnetic flux pinning mechanisms in niobium-titanium (Nb-Ti) thin films. The thin films were prepared via magnetron 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 2.0 K to 15.0 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 9.2 K at zero field. Magnetization loops revealed a high critical current density (Jc) exceeding 3.5 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 11.4 T by applying the Werthamer-Helfand-Hohenberg theoretical model. These findings demonstrate that nanoscale grain boundary control significantly improves vortex lattice stability, offering structural strategies for high-field superconducting applications.

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

Manuscript Timeline: Received: July 14, 2014; Revised: September 02, 2014; Accepted: September 24, 2014; Published: November 12, 2014

Citation: Semenov, O. K., & Vance, A. L. (2014). Superconducting Phase Transitions and Magnetic Flux Pinning Mechanisms in Niobium-Titanium Thin Films. International Journal of Physics, 5(11), 81–88.

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