Unusual Ground State Properties of the Kondo-Lattice Compound Yb2Ir3Ge5

TL;DR

This study characterizes the new Yb2Ir3Ge5 compound, revealing its orthorhombic structure, Kondo lattice behavior, mixed valence Yb ions, and potential magnetic ordering below 0.4 K, contributing to understanding complex ground states in Yb-based materials.

Contribution

It reports the synthesis, structural analysis, and physical properties of Yb2Ir3Ge5, highlighting its unusual ground state and mixed valence Yb ions, which is novel compared to similar compounds.

Findings

Yb2Ir3Ge5 has orthorhombic structure unlike related tetragonal compounds.

Displays typical Kondo lattice behavior with no ordering down to 0.4 K.

Yb ions show evidence of mixed valence states.

Abstract

We report sample preparation, structure, electrical resistivity, magnetic susceptibility and heat capacity studies of a new compound Yb$_2$Ir$_3$Ge$_5$. We find that this compound crystallizes in an orthorhombic structure with a space group PMMN unlike the compound Ce$_2$Ir$_3$Ge$_5$ which crystallizes in the tetragonal IBAM (U$_2$Co$_3$Si$_5$ type) structure. Our resistivity measurements indicate that the compound Yb$_2$Ir$_3$Ge$_5$ behaves like a typical Kondo lattice system with no ordering down to 0.4 K. However, a Curie-Weiss fit of the inverse magnetic susceptibility above 100 K gives an effective moment of only 3.66 $\mu$$_B$ which is considerably less than the theoretical value of 4.54 $\mu$$_B$ for magnetic Yb$^3+$ ions. The value of $\theta_{P}$ = -15.19 K is also considerably higher indicating the presence of strong hybridization. An upturn in the low temperature heat capacity gives an indication that the system may order magnetically just below the lowest temperature of our heat capacity measurements (0.4 K). The structure contains two sites for Yb ions and the present investigation suggests that Yb may be trivalent in one site while it may be significantly lower (close to divalent) in the other.