Magnetic and Superconducting Properties of FeAs-based High-Tc Superconductors with Gd

TL;DR

This study demonstrates that high-pressure synthesis is essential for producing high-Tc GdFeAs-based superconductors with nearly single-phase purity, achieving critical temperatures up to 53K and indicating very high upper critical fields.

Contribution

The paper introduces a high-pressure synthesis method for GdFeAs-based superconductors, resulting in nearly single-phase materials with high critical temperatures and potential for high magnetic field applications.

Findings

High-pressure synthesis yields nearly single-phase superconductors.

Critical temperatures range from 40 to 53K.

Estimated upper critical field Hc2 is approximately 130T.

Abstract

We report on successful synthesis under high pressure of a series of polycrystalline GdFeAs O_{1-x}F_x high-Tc superconductors with different oxygen deficiency x=0.12 - 0.16 and also with no fluorine. We have found that the high-pressure synthesis technique is crucial for obtaining almost single-phase superconducting materials: by synthesizing the same compounds with no pressure in ampoules we obtained non-superconducting materials with an admixture of incidental phases. Critical temperature for all the materials was in the range 40 to 53K. The temperature derivative of the critical field dHc2/dT is remarkably high, indicating potentially high value of the second critical field Hc2 ~ 130T.