${}^{57}$Fe Mössbauer study of stoichiometric iron based superconductor CaKFe${}_4$As${}_4$: a comparison to KFe${}_2$As${}_2$ and CaFe${}_2$As${}_2$

Sergey L. Bud'ko, Tai Kong, William R. Meier +2

${}^{57}$Fe Mössbauer spectra at different temperatures between $\sim 5$ K and $\sim 300$ K were measured on an oriented mosaic of single crystals of CaKFe${}_4$As${}_4$ . The data indic…