Abstract
Quantum materials display rich and myriad types of magnetic, electronic, and structural ordering, often with these ordering modes either competing with one another or “intertwining,” that is, reinforcing one another. Low-dimensional quantum materials influenced strongly by competing interactions and/or geometric frustration are particularly susceptible to such ordering phenomena and thus offer fertile ground for understanding the consequent emergent collective quantum phenomena. Such is the case of the quasi-2D materials (, Pr), in which intertwined charge- and spin-density waves (CDW and SDW) on the Ni sublattice have been identified and characterized. Not unexpectedly, these density waves are largely quasi-2D as a result of weak coupling between planes, compounded with magnetic frustration. In the case of , however, we show here that exchange coupling between the transition-metal and rare-earth sublattices upon cooling overcomes both obstacles, leading to a dimensional crossover into a fully 3D-ordered and coupled SDW state on both sublattices, as an induced moment on notionally nonmagnetic opens exchange pathways in the third dimension. In the process, the structure of the SDW on the Ni sublattice is irreversibly altered, an effect that survives reheating of the material until the underlying CDW melts. This “bootstrapping” mechanism linking incommensurate SDWs on the two sublattices illustrates a new member of the multitude of quantum states that low-dimensional magnets can express, driven by coupled orders and modulated by frustrated exchange pathways.
- Received 16 August 2022
- Revised 1 September 2023
- Accepted 8 September 2023
DOI:https://doi.org/10.1103/PhysRevX.13.041018
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Confinement of quantum spins and electric charges to chains and planes can lead to behavior that is markedly distinct from that of fully 3D matter. Crossovers between lower and higher dimensions are of interest because they reveal how electronic or magnetic interactions can evolve and compete as energy scales change. Here, we report on a novel type of dimensional crossover in a quasi-2D material in which crosstalk between two types of 2D magnetic order “bootstraps” a 3D magnetic order and irreversibly imprints a new metastable sublattice magnetization that survives substantial heating.
Our focus is the layered transition-metal oxide , in which coupled charge- and spin-density waves on the nickel sublattice are known to form in 2D because of weak 3D coupling between planes. By analyzing single-crystal neutron and resonant x-ray scattering, we now find that exchange coupling between the transition metal and rare-earth sublattices leads to a crossover into a fully 3D ordered and coupled spin-density-wave state on both sublattices. We explain this dimensional crossover and the metastability of the new spin-density-wave phase as resulting from 3D exchange pathways opening through an induced moment on the notionally nonmagnetic ions.
This bootstrapping mechanism linking incommensurate spin density waves on two sublattices illustrates a new member of the many quantum states that low-dimensional magnets can express, shaped by coupled orders and modulated by frustrated exchange pathways. Such an approach offers a new design rule to promote such dimensional crossovers and is thus of fundamental importance to our understanding of quantum matter.
