Reentrant superconductivity in YBa$_2$Cu$_3$O$_{7-d}$ microstructured particles

TL;DR

This study reports the observation of reentrant superconductivity in YBCO particles, driven by the interplay of bulk superconductivity and surface ferromagnetism influenced by microstructure and size effects.

Contribution

It reveals the role of microstructure and particle size in inducing reentrant superconductivity through surface ferromagnetism in YBCO particles.

Findings

Reentrant superconductivity observed in 385 nm YBCO particles.

Surface ferromagnetism coexists with bulk superconductivity.

Critical temperatures identified as approximately 92 K and 10 K.

Abstract

A reentrant superconducting effect was observed in YBCO particles as a consequence of their size and microstructure. It rises from the coexistence between bulk superconductivity and surface ferromagnetism, where the enhanced magneto-electric coupling induced by broken spatial-inversion symmetry in layers near structural defects plays a very important role on surface ferromagnetism. The study assumes grain boundaries inside the particles act as additional surface regions that enhance the ferromagnetic properties. Magnetic and superconducting properties as a function of particle size were studied. Particularly, the 385 nm particles which were the ones that exhibited the reentrant superconducting effect. The Ginzburg-Landau parameter and the critical temperatures are $k \sim 1.29$, T$_{c1}$ = 92 $\pm$ 5 K, and T$_{c2}$ = 10 $\pm$ 3 K.