Structural and superconducting properties in LaFeAs1-xSbxO1-yFy

TL;DR

This study investigates how antimony doping affects the structural and superconducting properties of LaFeAsO-based iron superconductors, revealing increased Tc up to 30 K and insights into magnetic and electronic changes.

Contribution

It provides new insights into Sb doping effects on lattice structure, magnetic order, and superconductivity in LaFeAsO-based materials, highlighting the role of chemical pressure.

Findings

Sb doping increases lattice parameters and Fe2As2 layer thickness.

Superconducting transition temperature reaches up to 30 K.

Sb doping recovers SDW order in optimally doped samples.

Abstract

We report the antimony (Sb) doping effect in a prototype system of iron-based supercon-ductors LaFeAsO1-yFy (y=0, 0.1, 0.15). X-ray powder diffraction indicates that the lattice pa-rameters increase with Sb content within the doping limit. Rietveld structural refinements show that, with the partial substitution of Sb for As, while the thickness of the Fe2As2 layers increases significantly, that of the La2O2 layers shrinks simultaneously. So a negative chemical pressure is indeed "applied" to the superconducting-active Fe2As2 layers, in con-trast to the effect of positive chemical pressure by the phosphorus doping. Electrical resis-tance and magnetic susceptibility measurements indicate that, while the Sb doping hardly influences the SDW anomaly in LaFeAsO, it recovers SDW order for the optimally-doped sample of y=0.1. In the meantime, the superconducting transition temperature can be raised up to 30 K in LaFeAs1-xSbxO1-yFy with x=0.1 and y=0.15. The Sb doping effects are discussed in term of both J1-J2 model and Fermi Surface (FS) nesting scenario.