Magnetic Ordering and Superconductivity in the RE$_2$Ir$_3$Ge$_5$ (RE = Y, La-Tm, Lu) System

TL;DR

This study explores the structural, electronic, and magnetic properties of RE$_2$Ir$_3$Ge$_5$ compounds, revealing structural variations, superconductivity in some members, and magnetic ordering behaviors linked to RKKY interactions.

Contribution

It provides new insights into the structural phases, resistivity behaviors, and magnetic properties of RE$_2$Ir$_3$Ge$_5$ compounds, including the discovery of superconductivity and magnetic ordering patterns.

Findings

Y and La-Dy compounds crystallize in tetragonal structure.

Er-Lu compounds form a new orthorhombic structure.

La$_2$Ir$_3$Ge$_5$ and Y$_2$Ir$_3$Ge$_5$ are superconducting below 1.8K and 2.5K.

Abstract

We find that the compounds for RE = Y, La-Dy, crystallize in the tetragonal Ibam (U$_2$Co$_3$Si$_5$ type) structure whereas the compounds for RE = Er-Lu, crystallize in a new orthorhombic structure with a space group Pmmn. Samples of Ho$_2$Ir$_3$Ge$_5$ were always found to be multiphase. The compounds for RE = Y to Dy which adopt the Ibam type structure show a metallic resistivity whereas the compounds with RE = Er, Tm and Lu show an anomalous behavior in the resistivity with a semiconducting increase in $\rho$ as we go down in temperature from 300K. Interestingly we had earlier found a positive temperature coefficient of resistivity for the Yb sample in the same temperature range. We will compare this behavior with similar observations in the compounds RE$_3$Ru$_4$Ge$_{13}$ and REBiPt. La$_2$Ir$_3$Ge$_5$ and Y$_2$Ir$_3$Ge$_5$ show bulk superconductivity below 1.8K and 2.5K respectively. Our results confirm that Ce$_2$Ir$_3$Ge$_5$ shows a Kondo lattice behavior and undergoes antiferromagnetic ordering below 8.5K. Most of the other compounds containing magnetic rare-earth elements undergo a single antiferromagnetic transition at low temperatures (T$\leq$12K) while Gd$_2$Ir$_3$Ge$_5$, Dy$_2$Ir$_3$Ge$_5$ and Nd$_2$Ir$_3$Ge$_5$ show multiple transitions. The T$_N$'s for most of the compounds roughly scale with the de Gennes factor. which suggests that the chief mechanism of interaction leading to the magnetic ordering of the magnetic moments may be the RKKY interaction.