Signatures of polarized chiral spin disproportionation in rare earth nickelates

Abstract

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.

6 pages, 4 figures

References in corpus (7)

• Ground state oxygen holes and the metal-insulator transition in the negative charge transfer rare-earth nickelates
• Physics of ultrathin films and heterostructures of rare earth nickelates
• Bond disproportionation and dynamical charge fluctuations in the perovskite rare earth nickelates
• Role of magnetic and orbital ordering at the metal-insulator transition in NdNiO3
• Tailoring the electronic transitions of NdNiO_3 films through (111)_pc oriented interfaces
• Complex magnetic order in nickelate slabs
• Raman spectroscopic evidence for multiferroicity in rare earth nickelate single crystals