Magnetic moment evolution and spin freezing in doped BaFe$_{2}$As$_{2}$
  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. 
Jonathan Pelliciari, Yaobo Huang, Kenji Ishii, Chenglin Zhang,   Pengcheng Dai, Gen Fu Chen, Lingyi Xing, Xiancheng Wang, Ch...
cond-mat.supr-con