Physical properties of the R3Pt23Si11 compounds with volatile rare earth: Sm, Eu, Tm and Yb

• R3Pt23Si11 with volatile rare earth Sm, Eu, Tm and Yb have been synthesized.
• Structural studies confirm that they crystallize in the same structure as Ce3Pt23Si11.
• For Eu- and Yb-3Pt23Si11 a divalent valence state is found for Eu and Yb.
• Eu- and Sm-3Pt23Si11 present a ferromagnetic order at 5.54 K and 10.12 K respectively.
• In Tm3Pt23Si11 no magnetic order is found down to 0.36 K, Yb3Pt23Si11 is diamagnetic.

The new R3Pt23Si11 series, where R is a rare earth, has been completed with the synthesis of three new compounds with volatile rare earth: R=Eu, Sm, and Tm. The studies of their physical properties have been performed along with those of the Yb3Pt23Si11 compound. The X-ray powder diffraction patterns confirm that they all crystallize in the same face-centered cubic structure, space group Fm3¯m, as the rest of the series. The refinements of the diffraction patterns show an anomalously high lattice parameter in Eu3Pt23Si11 and Yb3Pt23Si11, indicating a divalent valence state for Eu and Yb. This 2+ valence state for Eu and Yb ions is confirmed by the magnetic measurements. A ferromagnetic order is observed at TC=5.54±0.07 K and 10.12±0.07 K in Eu3Pt23Si11 and Sm3Pt23Si11 respectively. In Tm3Pt23Si11 no magnetic order is found down to 0.36 K while Yb3Pt23Si11 reveals a diamagnetic behavior. At low temperatures the spontaneous moment, Ms, in Eu3Pt23Si11 is in agreement with a L=0, S=7/2 state for the Eu2+ ion. On the contrary in Sm3Pt23Si11, Ms is far below the 0.714μB expected for the saturated moment of the Sm3+ in the J=7/2 ground state multiplet.