Signatures of polarized chiral spin disproportionation in rare earth nickelates

• Published in: arXiv.org
• Main Authors: Li, Jiarui, Green, Robert J, Domínguez, Claribel, Levitan, Abraham, Tseng, Yi, Catalano, Sara, Fowlie, Jennifer, Sutarto, Ronny, Rodolakis, Fanny, Korol, Lucas, McChesney, Jessica L, Freeland, John W, Van der Marel, Dirk, Gibert, Marta, Comin, Riccardo
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 05.09.2024
• Subjects: Antiferromagnetism; Chirality; Coupling; Crystallography; Disproportionation; Electron spin; Ferroelectricity; Helicity; Ligands; Phase transitions; Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Physics - Strongly Correlated Electrons; Single crystals; Thin films; X-ray scattering
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2408.17450

In rare earth nickelates (RENiO\(_3\)), electron-lattice coupling drives a concurrent metal-to-insulator and bond disproportionation phase transition whose microscopic origin has long been the subject of active debate. Of several proposed mechanisms, here we test the hypothesis that pairs of self-doped ligand holes spatially condense to provide local spin moments that are antiferromagnetically coupled to Ni spins. These singlet-like states provide a basis for long-range bond and spiral spin order. Using magnetic resonant X-ray scattering on NdNiO\(_3\) thin films, we observe the chiral nature of the spin-disproportionated state, with spin spirals propagating along the crystallographic (101)\(_\mathrm{ortho}\) direction. These spin spirals are found to preferentially couple to X-ray helicity, establishing the presence of a hitherto-unobserved macroscopic chirality. The presence of this chiral magnetic configuration suggests a potential multiferroic coupling between the noncollinear magnetic arrangement and improper ferroelectric behavior as observed in prior studies on NdNiO\(_3\) (101)\(_\mathrm{ortho}\) films and RENiO\(_3\) single crystals. Experimentally constrained theoretical double-cluster calculations confirm the presence of an energetically stable spin-disproportionated state with Zhang-Rice singlet-like combinations of Ni and ligand moments.