# Complex magnetic order in nickelate slabs

## TL;DR

This study investigates magnetic order in nickelate slabs, demonstrating the ability to realize different magnetic structures depending on slab thickness, and combining experimental and theoretical methods to analyze magnetic moments.

## Contribution

It introduces a model system of NdNiO3 slabs in NdGaO3, showing how polarized RXS and density functional theory predict and analyze complex magnetic structures.

## Key findings

- Both collinear and non-collinear magnetic structures are realized depending on slab thickness.
- Density functional theory accurately predicts the magnetic structure crossover.
- RXS combined with a double cluster model determines magnetic moment ratios.

## Abstract

Magnetic ordering phenomena have a profound influence on the macroscopic properties of correlated-electron materials, but their realistic prediction remains a formidable challenge. An archetypical example is the ternary nickel oxide system RNiO3 (R = rare earth), where the period-four magnetic order with proposals of collinear and non-collinear structures and the amplitude of magnetic moments on different Ni sublattices have been subjects of debate for decades. Here we introduce an elementary model system - NdNiO3 slabs embedded in a non-magnetic NdGaO3 matrix - and use polarized resonant x-ray scattering (RXS) to show that both collinear and non-collinear magnetic structures can be realized, depending on the slab thickness. The crossover between both spin structures is correctly predicted by density functional theory and can be qualitatively understood in a low-energy spin model. We further demonstrate that the amplitude ratio of magnetic moments in neighboring NiO6 octahedra can be accurately determined by RXS in combination with a correlated double cluster model. Targeted synthesis of model systems with controlled thickness and synergistic application of polarized RXS and ab-initio theory thus provide new perspectives for research on complex magnetism, in analogy to two-dimensional materials created by exfoliation.

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Source: https://tomesphere.com/paper/1905.04160