Anisotropic superconducting properties of aligned Sm$_{0.95}$La$_{0.05}$FeAsO$_{0.85}$F$_{0.15}$ microcrystalline powder

TL;DR

This study investigates the anisotropic superconducting properties of aligned Sm$_{0.95}$La$_{0.05}$FeAsO$_{0.85}$F$_{0.15}$ microcrystalline powder, revealing anisotropic diamagnetic behavior and critical parameters that may relate to the pairing mechanism.

Contribution

It demonstrates room-temperature alignment of microcrystalline powder using magnetic fluctuations and characterizes its anisotropic superconducting properties for the first time.

Findings

Anisotropic diamagnetic ratio $ ext{chi}_c/ ext{chi}_{ab} ext{~} 2.4$

Zero-temperature penetration depths $ ext{lambda}_c(0)=280$ nm, $ ext{lambda}_{ab}(0)=120$ nm

Aligned powder shows anisotropic phase diagram and magnetic fluctuations potentially linked to pairing mechanism

Abstract

The Sm$_{0.95}$La$_{0.05}$FeAsO$_{0.85}$F$_{0.15}$ compound is a quasi-2D layered superconductor with a superconducting transition temperature T$_c$ = 52 K. Due to the Fe spin-orbital related anisotropic exchange coupling (antiferromagnetic or ferromagnetic fluctuation), the tetragonal microcrystalline powder can be aligned at room temperature using the field-rotation method where the tetragonal $\it{ab}$-plane is parallel to the aligned magnetic field B$_{a}$ and $\it{c}$-axis along the rotation axis. Anisotropic superconducting properties with anisotropic diamagnetic ratio $\chi_{c}/\chi_{ab}\sim$ 2.4 + 0.6 was observed from low field susceptibility $\chi$(T) and magnetization M(B$_{a}$). The anisotropic low-field phase diagram with the variation of lower critical field gives a zero-temperature penetration depth $\lambda_{c}$(0) = 280 nm and $\lambda_{ab}$(0) = 120 nm. The magnetic fluctuation used for powder alignment at 300 K may be related with the pairing mechanism of superconductivity at lower temperature.