Observation of the Griffiths phase in the ternary nitrides Sn1−xNFe3+x

We report the synthesis and magnetic properties of ternary iron nitride compounds ${\mathrm{Sn}}_{1\ensuremath{-}x}\mathrm{N}{\mathrm{Fe}}_{3+x}$ $(0\ensuremath{\le}x\ensuremath{\le}0.4)$. The magnetic frustration state is found in $\mathrm{SnN}{\mathrm{Fe}}_{3}$, and the antiferromagnetic (AFM) exchange is dominant in ${\mathrm{Sn}}_{0.95}\mathrm{N}{\mathrm{Fe}}_{3.05}$ and ${\mathrm{Sn}}_{0.9}\mathrm{N}{\mathrm{Fe}}_{3.1}$, and then the ferromagnetic (FM) interaction occurs in ${\mathrm{Sn}}_{1\ensuremath{-}x}\mathrm{N}{\mathrm{Fe}}_{3+x}$ $(0.2\ensuremath{\le}x\ensuremath{\le}0.4)$. Interestingly, the Griffiths phase is observed in $x=0.1$, 0.2, caused by the FM coupling competing over the AFM one and forming the short-range FM cluster. At the same time, the competitions between the AFM and FM interactions lead to a spin-glass behavior, which is embodied most evidently in ${\mathrm{Sn}}_{0.7}\mathrm{N}{\mathrm{Fe}}_{3.3}$ and further confirmed by the corresponding characteristic fitting parameters $({\ensuremath{\tau}}_{0}=8.89\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}\phantom{\rule{0.16em}{0ex}}\mathrm{s},$ ${T}_{0}=25\phantom{\rule{0.16em}{0ex}}\mathrm{K}, \mathrm{and} zv=6.56)$. In addition, density functional theory (DFT) calculations exhibit the magnetic ground states, magnetic moments contribution, and bonds nature of Sn-Fe and N-Fe. The results of DFT calculations disclose some detailed magnetic interactions, which are demonstrated to be an evidential response to the interesting magnetic behavior in ${\mathrm{Sn}}_{1\ensuremath{-}x}\mathrm{N}{\mathrm{Fe}}_{3+x}$ compounds.