Anisotropic magnetism, resistivity, London penetration depth and magneto-optical imaging of superconducting K0.80Fe1.76Se2 single crystals

TL;DR

This study reports on the synthesis, detailed characterization, and magnetic and electrical properties of superconducting K0.80Fe1.76Se2 single crystals, revealing anisotropic behaviors and a broad transition near 30 K.

Contribution

It provides new insights into the growth process, composition, and anisotropic superconducting properties of K0.80Fe1.76Se2 single crystals, including magneto-optical imaging results.

Findings

Crystals grow from a ternary solution liquid at high temperatures.

Superconductivity observed with Tc around 30 K.

Anisotropic magnetic susceptibility and resistivity behaviors.

Abstract

Single crystals of K0.80Fe1.76Se2.02 were suscessfully grown from a ternary solution. We show that although crystals form when cooling a near stoichiometric melt, crystals are actually growing out of a ternary solution that remains liquid to at least 850 C. We investigated their chemical composition, anisotropic magnetic susceptibility and resistivity, specific heat, thermoelectric power, London penetration depth and flux penetration via magneto-optical imaging. Whereas the samples appear to be homogeneously superconducting at low temperatures, there appears to be a broadened transtion range close to Tc ~ 30 K that may be associated with small variations in stociometry.