CrFe2Ge2: Investigation of novel ferromagnetic material of Fe13Ge8-type crystal

We successfully synthesized a novel intermetallic compound $\mathrm{C}\mathrm{r}\mathrm{F}{\mathrm{e}}_2\mathrm{G}{\mathrm{e}}_2$ with the $\mathrm{F}{\mathrm{e}}_{13}\mathrm{G}{\mathrm{e}}_8$-type crystal structure. A structural study is presented combining single-crystal X-ray diffraction and Mössbauer spectroscopy analysis, confirming the presence of two distinct Fe sublattices. $\mathrm{C}\mathrm{r}\mathrm{F}{\mathrm{e}}_2\mathrm{G}{\mathrm{e}}_2$ exhibits a metallic ferromagnetic state with $T_C\approx 200\mathrm{K}$. This material does not follow the usual $M^2\propto H\mathrm{/}M$ Arrott law, rather a modified Arrott law is obeyed in this material. The critical exponents determined from detailed analysis of modified Arrott plots were found to be $\beta =0.392$, $\gamma =1.309$ and $\delta =4.26$ obtained from the critical isotherm at $T_{\mathrm{C}}=200\mathrm{K}$. Self-consistency and reliability of the critical exponent analysis were verified by the Widom scaling law and scaling equations. Using the results from renormalization group calculation, the critical behavior of $\mathrm{C}\mathrm{r}\mathrm{F}{\mathrm{e}}_2\mathrm{G}{\mathrm{e}}_2$ is akin to that of a $d=3,n=3$ ferromagnet in which the magnetic exhange distance is found to decay as $J(r)\approx r^{-4.86}$ with long-range magnetic coupling. The evaluated Rhodes-Wohlfarth ratio of $\sim 3$ points to an itinerant ferromagnetic ground state. Low-temperature measurements of resistivity, $p(T)$, and specific heat, $C_P(T)$, reveal a pronounced contribution from electron-magnon scattering.