Anisotropic spin stripe domains in bilayer La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub>.

Gupta, Naman K; Gong, Rantong; Wu, Yi; Kang, Mingu; Parzyck, Christopher T; Gregory, Benjamin Z; Costa, Noah; Sutarto, Ronny et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The discovery of superconductivity in La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> under pressure has motivated the investigation of a parent spin density wave (SDW) state, which could provide the underlying pairing interaction. Here, we employ resonant soft x-ray scattering and polarimetry on thin films of bilayer La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> to determine that the magnetic structure of the SDW forms unidirectional diagonal spin stripes with moments lying within the NiO<sub>2</sub> plane and perpendicular to Q<sub>SDW</sub>, but without evidence of the strong charge disproportionation typically associated with other nickelates. These stripes form anisotropic domains with shorter correlation lengths perpendicular versus parallel to Q<sub>SDW</sub>, revealing nanoscale rotational and translational symmetry breaking analogous to the cuprate and Fe-based superconductors, with possible Bloch-like antiferromagnetic domain walls separating orthogonal domains.