A M\"ossbauer study of the magneto-structural coupling effect in   SrFe$_2$As$_2$ and SrFeAsF
  In the present paper, we report a comparison study of SrFe$_2$As$_2$ and SrFeAsF using M\"ossbauer spectroscopy. The temperature dependence of the magnetic hyperfine field is fitted with a modified Bean-Rodbell model. The results give much smaller magnetic moment and magneto-structural coupling effect for SrFeAsF, which may be understood as due to different inter-layer properties of the two compounds. 
Zhiwei Li, Xiaoming Ma, Hua Pang, and Fashen Li
cond-mat.supr-con