Preferential site ordering alters the magnetic structure of Sm$_3$Ru$_4$Sn$_{13-x}$Ge$_x$ ($x = 0$-2)

TL;DR

This study explores how preferential site occupancy of Ge in Sm$_3$Ru$_4$Sn$_{13-x}$Ge$_x$ alters its magnetic ordering, revealing a method to tune magnetic properties in intermetallic compounds through controlled alloying.

Contribution

It demonstrates that selective Ge alloying at specific Wyckoff sites enables precise tuning of magnetic structures in Sm$_3$Ru$_4$Sn$_{13-x}$Ge$_x$, advancing design principles for quantum phases.

Findings

Ge shows preferential occupancy in the crystal structure.

Magnetic transition temperatures decrease with Ge alloying.

Alloying induces magnetic frustration and modifies electronic states.

Abstract

An important aspect of materials research is the ability to tune different physical properties through controlled alloying. The Ln$_3$M$_4$X$_{13}$ (Ln = Lanthanide, M = Transition Metal, X = Tetrel) filled skutterudite family is of interest due to the tunability of its constituent components and their effects on physical properties, such as superconductivity and complex magnetism. In this work, Sm$_3$Ru$_4$Sn$_{13-x}$Ge$_x$ (x = 0 -- 2) was synthesized via excess Sn-flux and characterized using powder and single-crystal X-ray diffraction, magnetometry, X-ray photoelectron spectroscopy, and heat capacity. Sm$_3$Ru$_4$Sn$_{13}$ and its Ge-solid-solution members crystallize in the Pm-3n space group, which has two unique Wyckoff positions for the tetrel (X) site. In the solid solution members, Ge shows preferential occupancy for one of the two Wyckoff sites, reaching $\sim$60$\%$ and 100$\%$ occupancy when x = 1 and 2, respectively. Magnetometry and heat capacity measurements of Sm$_3$Ru$_4$Sn$_{13}$ indicated antiferromagnetic ordering at $T_N$ = 7.3 K. However, Sm$_3$Ru$_4$Sn$_{12}$Ge and Sm$_3$Ru$_4$Sn$_{11}$Ge$_2$ showed notably lower-temperature antiferromagnetic phase transitions with substantial peak-broadening at $T_N$ = 5.5 K and 4.1 K, respectively. These data suggest that alloying Ge into Sm$_3$Ru$_4$Sn$_{13}$ causes magnetic frustration within the structure, likely attributable to a change in the density of states from additional Ge $p$ states at the Fermi level. This work demonstrates that preferentially alloying Ge in Sm$_3$Ru$_4$Sn$_{13-x}$Ge$_x$ allows for more precise tunability of its magnetic structure, elucidating design principles for different quantum phases in intermetallic materials.