Spin stripe order in a square planar trilayer nickelate

June 30, 2019

In a study published in Physical Review Letters, researchers reported single crystal neutron diffraction measurements that establish that the ground state is indeed magnetic.

(a) Uncorrelated trilayer model for the spin ordering, displayed layer by layer. Ni1+ sites are shown in blue, and nonmagnetic Ni2+sites are shown in red. Moments pointing into the plot are shown by ⊗, while moments pointing out of the plot are shown as ⊙. The intra-trilayer coupling as well as the coupling across stripes is labeled. (b) Three-dimensional perspective of the structure shown in (a).

Scientific Achievement

Single crystal neutron scattering definitively reveals antiferromagnetic spin stripes that are commensurate with and strongly coupled to charge stripes at a semiconductor-insulator transition in La₄Ni₃O₈.

Significance and Impact

Understanding the coupling between charge and spin is key in the exploration of potential high-T_C physics in copper-free oxides.

Research Details

Both polarized and unpolarized single crystal neutron diffraction, were performed on La₄Ni₃O₈ with triple-axis instruments at HFIR and NIST Center for Neutron Research.
The semiconductor to insulator transition is accompanied by simultaneous charge and antiferromagnetic spin stripe order that occurs within square planar, Ni-O trilayers.
Both experiment and density functional theory calculations indicate that spins point along the c‑axis, in contrast to cuprates.
The spin and charge stripe order parameters are strongly coupled; uniquely, neither order parameter is secondary to the other.

DOI: 10.1103/PhysRevLett.122.247201

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