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

Abstract

We successfully synthesized a novel intermetallic compound $\rm CrFe_2Ge_2$ with the $\rm Fe_{13}Ge_{8}$-type crystal structure. A structural study is presented combining single-crystal X-ray diffraction and M\"{o}ssbauer spectroscopy analysis, confirming the presence of two distinct Fe sublattices. $\rm CrFe_2Ge_2$ exhibits a metallic ferromagnetic state with $T_C \approx \rm 200~K$. This material does not follow the usual $M^2 \propto H/M$ 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_{\rm C} =\rm 200~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 $\rm CrFe_2Ge_2$ 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.