Ferromagnetic spin fluctuation in LaFeAsO1-xFx

TL;DR

This study investigates the role of ferromagnetic spin fluctuations in LaFeAsO1-xFx superconductors, revealing that such fluctuations likely mediate superconductivity, supported by heat capacity and magnetic susceptibility measurements indicating nearly ferromagnetic behavior.

Contribution

It provides experimental evidence linking ferromagnetic spin fluctuations to superconductivity in LaFeAsO1-xFx, a novel insight into the pairing mechanism in this material.

Findings

Observation of T3lnT term in heat capacity

Large Wilson ratio indicating ferromagnetic tendencies

Superconductivity likely mediated by ferromagnetic spin fluctuations

Abstract

The F doped LaFeAsO, a recently discovered superconductor with the high Tc of 26 K, has been studied by the resistivity, magnetic susceptibility, and heat capacity measurements in the F doping range from 0 to 0.14 (x in LaFeAsO1-xFx). In the low temperature region, a T3lnT term in the heat capacity and a T2 term in the magnetic susceptibility, which are derived from the spin fluctuation, are observed. The nearly ferromagnetic nature evidenced by a large Wilson ratio (6.5 for x = 0, and 11.2 for x = 0.025) suggests that the superconductivity in the LaFeAsO system is mediated by ferromagnetic spin fluctuation.