Combinatorial search of superconductivity in Fe-B composition spreads

TL;DR

This study explores superconductivity in Fe-B thin film composition spreads, discovering a trace of superconducting phase near FeB₂ composition with a transition at 4K, influenced by magnetic fields.

Contribution

It reports the experimental fabrication and characterization of Fe-B composition spreads, identifying a potential superconducting phase near FeB₂, which was previously predicted theoretically.

Findings

Superconductivity observed at 4K in Fe-B films.

Superconductivity suppressed by magnetic field up to 2 Tesla.

Trace superconducting phase found near FeB₂ composition.

Abstract

We have fabricated Fe-B thin film composition spreads in search of possible superconducting phases following a theoretical prediction by Kolmogorov et al.^1 Co-sputtering was used to deposit spreads covering a large compositional region of the Fe-B binary phase diagram. A trace of superconducting phase was found in the nanocrystalline part of the spread, where the film undergoes a metal to insulator transition as a function of composition in a region with the average composition of FeB_2. The resistance drop occurs at 4K, and a diamagnetic signal has also been detected at the same temperature. The superconductivity is suppressible in the magnetic field up to 2 Tesla.