Abstract
Yb-based triangular lattice materials have attracted significant attention due to their potential for hosting exotic magnetic quantum states. In this paper, we report the structural, magnetic, and thermodynamic properties of two Yb triangular lattice compounds with vacancy disorder at nonmagnetic Cu sites: CuYbSe2 and Cu2.73YbP2. Single-crystal x-ray diffraction determines notable Cu-site vacancies in both materials. Unlike a single Cu site with 0.5 occupancy in CuYbSe2, Cu2.73YbP2 only presents 27% vacancies on one of three Cu sites. Magnetic susceptibility measurements indicate dominant antiferromagnetic interactions between Yb3+ ions. The effective magnetic moment is consistent with an effective spin-1/2 state of Yb3+. CuYbSe2 exhibits strong magnetic anisotropy between in-plane and out-of-plane directions with the estimated exchange interactions Ja/kB=6.48K and Jc/kB=2.55K. No magnetic ordering is observed down to 0.4 K, supporting its quantum disordered ground state and candidacy as a quantum spin liquid. In contrast, Cu2.73YbP2 shows clear evidence of spin freezing at 4.5 K in both magnetization and heat capacity data, indicating a spin glass state. The field-induced magnetic orders are found in CuYbSe2. These results highlight the critical role of structural vacancies in perturbing Yb-based triangular lattices. We demonstrate that while the intrinsic Yb triangular lattices are comparable, the presence of Cu vacancies can fundamentally alter the magnetic ground state—tuning the system between quantum disordered and spin glass behavior.
| Original language | English |
|---|---|
| Article number | 084406 |
| Journal | Physical Review Materials |
| Volume | 9 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 8 2025 |
Funding
We acknowledge Athena Sefat for providing previous intellectual leadership on the discovery and synthesizing of these quantum spin liquid materials. The research at the Oak Ridge National Laboratory (ORNL) is supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES). This research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. E.F. and H.C. acknowledge the support from U.S. DOE BES Early Career Award No. KC0402010 under Contract No. DE-AC05-00OR22725. The beam time was allocated to DEMAND on Proposal No. IPTS-26476.This manuscript has been coauthored by employees of ORNL, which is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevo-cable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan [37]. We acknowledge Athena Sefat for providing previous intellectual leadership on the discovery and synthesizing of these quantum spin liquid materials. The research at the Oak Ridge National Laboratory (ORNL) is supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES). This research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. E.F. and H.C. acknowledge the support from U.S. DOE BES Early Career Award No. KC0402010 under Contract No. DE-AC05-00OR22725. The beam time was allocated to DEMAND on Proposal No. IPTS-26476. This manuscript has been coauthored by employees of ORNL, which is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevo-cable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan .