Ferromagnetic ordering of minority Ce${}^{3+}$ spins in a quasi-skutterudite Ce${}_3$Os${}_4$Ge${}_{13}$ single crystal

Abstract

We report site disorder driven ferromagnetic ordering of nearly 8$\%$ Ce atoms in single crystalline Ce${}_3$Os${}_4$Ge${}_{13}$ below 0.5~K. Ce${}_3$Os${}_4$Ge${}_{13}$ crystallizes in a cubic structure with space group $Pm\bar{3}n$. The structural analysis shows the presence of site-disorder in the system, where 2(a) Ge site is partially occupied by the Ce atoms. Due to the small Ce $4f$-ligand hybridization, these Ce atoms are in the Ce${}^{3+}$ (magnetic) state while rest of the Ce atoms in the unit cell are in Ce${}^{4-\delta }$ (non-magnetic) state. The heat capacity shows a peak below 0.5~K corresponding to the ferromagnetic ordering of the Ce${}^{3+}$ moments. The ferromagnetic ordering below 0.5~K is also seen in the ac-susceptibility data. At low temperatures (1.8~K$\le T\le 6$~K), the magnetization shows $log(T)$ dependence, whereas the resistivity shows power law ($T^n$) temperature dependence indicating the non-Fermi liquid behavior of the quasiparticles.

10 pages, 5 figures