Chiral-crystal-structure transformations and magnetic states of R3Rh4Sn13 ( R=La and Ce)

Abstract

Structural studies were performed on ${R}_{3}{\mathrm{Rh}}_{4}{\mathrm{Sn}}_{13}$ ($R$=La and Ce). X-ray diffraction measurements on single-crystalline samples of both Rh-based compounds, which were synthesized by the molten Sn-flux method, have revealed structural transformations below ${T}_{\mathrm{D}}\ensuremath{\simeq}$ 350 K. The low-temperature superstructures are characterized by the wave vector $\mathbit{q}=(1/2,1/2,0)$. The space group in the low-temperature phases of both compounds is chiral cubic $I{2}_{1}3$, which is the same as that of ${R}_{3}{\mathrm{Co}}_{4}{\mathrm{Sn}}_{13}$ ($R$=La and Ce). Neutron diffraction measurement of ${\mathrm{Ce}}_{3}{\mathrm{Rh}}_{4}{\mathrm{Sn}}_{13}$ revealed no magnetic long-range order below the temperature of the specific-heat peaks at 1.2 and 1.8 K. The low-temperature magnetic state in the chiral phase is that of a paramagnetic semimetal, whereas the dynamical spin correlation of Ce is deduced from the specific-heat data, as found previously in ${\mathrm{Ce}}_{3}{\mathrm{Co}}_{4}{\mathrm{Sn}}_{13}$.