Stability Frontiers in the <i>AM</i><sub>6</sub><i>X</i><sub>6</sub> Kagome Metals: The <i>Ln</i>Nb<sub>6</sub>Sn<sub>6</sub> (<i>Ln</i>:Ce–Lu,Y) Family and Density-Wave Transition in LuNb<sub>6</sub>Sn<sub>6</sub>
Brenden R. Ortiz, William R. Meier, Ganesh Pokharel, Juan R. Chamorro, Fazhi Yang, Shirin Mozaffari, A. Thaler, Steven J. Gomez Alvarado, Heda Zhang, David Parker, German D. Samolyuk, Joseph A. M. Paddison, Jiaqiang Yan, Feng Ye, Suchismita Sarker, Stephen D. Wilson, Hu Miao, David Mandrus, Michael A. McGuire
Abstract
The kagome motif is a versatile platform for condensed matter physics, hosting rich interactions between magnetic, electronic, and structural degrees of freedom. In recent years, the discovery of a charge density wave (CDW) in the AV 3 Sb 5 superconductors and structurally-derived bond density waves (BDW) in FeGe and ScV 6 Sn 6 have stoked the search for new kagome platforms broadly exhibiting density wave (DW) transitions. In this work, we evaluate the known AM 6 X 6 chemistries and construct a stability diagram that summarizes the structural relationships among the >125 member family. Subsequently, we introduce our discovery of the broader Ln Nb 6 Sn 6 ( Ln:Ce–Nd,Sm,Gd–Tm,Lu,Y) family of kagome metals and an analogous DW transition in LuNb 6 Sn 6 . Our X-ray scattering measurements clearly indicate a (1/3, 1/3, 1/3) ordering wave vector ( 3 × 3 × 3 superlattice) and diffuse scattering on half-integer L -planes. Our analysis of the structural data supports the “rattling mode” DW model proposed for ScV 6 Sn 6 and paints a detailed picture of the steric interactions between the rare-earth filler element and the host Nb–Sn kagome scaffolding. We also provide a broad survey of the magnetic properties within the HfFe 6 Ge 6 -type Ln Nb 6 Sn 6 members, revealing a number of complex antiferromagnetic and metamagnetic transitions throughout the family. This work integrates our new Ln Nb 6 Sn 6 series of compounds into the broader AM 6 X 6 family, providing new material platforms and forging a new route forward at the frontier of kagome metal research.