Magnetic moment evolution and spin freezing in doped BaFe$_{2}$As$_{2}$

TL;DR

This study uses Fe-Kβ X-ray emission spectroscopy to investigate how magnetic moments evolve with doping and temperature in BaFe₂As₂, revealing asymmetric behavior and spin freezing phenomena influenced by Hund's coupling.

Contribution

It provides new insights into the doping-dependent magnetic moments and spin states in BaFe₂As₂, highlighting the importance of Hund's coupling and electronic correlations.

Findings

Magnetic moments show asymmetric doping dependence.

Temperature increases induce spin freezing in hole-doped samples.

Fully localized or itinerant models are insufficient for describing Fe pnictides.

Abstract

Fe-K$_{\beta}$ X-ray emission spectroscopy measurements reveal an asymmetric doping dependence of the magnetic moments $\mu_\text{bare}$ in electron- and hole-doped BaFe$_{2}$As$_{2}$. At low temperature, $\mu_\text{bare}$ is nearly constant in hole-doped samples, whereas it decreases upon electron doping. Increasing temperature substantially enhances $\mu_\text{bare}$ in the hole-doped region, which is naturally explained by the theoretically predicted crossover into a spin-frozen state. Our measurements demonstrate the importance of Hund's coupling and electronic correlations, especially for hole-doped BaFe$_{2}$As$_{2}$, and the inadequacy of a fully localized or fully itinerant description of the 122 family of Fe pnictides.