Spectroscopy of stripe order in La1.8Sr0.2NiO4 using resonant soft x-ray diffraction

TL;DR

This study uses resonant soft x-ray diffraction to investigate the charge and spin order in La1.8Sr0.2NiO4, revealing detailed local symmetry and hole distribution within the NiO2 layers.

Contribution

It provides new insights into the local symmetry and hole localization in La1.8Sr0.2NiO4 using resonant soft x-ray diffraction near Ni L2,3 edges.

Findings

Charge and spin order are enhanced at Ni L2,3 edges.

Holes mainly reside on in-plane oxygens around Ni2+ sites.

Both magnetic and charge orders are within NiO2 layers.

Abstract

Strong resonant enhancements of the charge-order and spin-order superstructure-diffraction intensities in La1.8Sr0.2NiO4 are observed when x-ray energies in the vicinity of the Ni L2,3 absorption edges are used. The pronounced photon-energy and polarization dependences of these diffraction intensities allow for a critical determination of the local symmetry of the ordered spin and charge carriers. We found that not only the antiferromagnetic order but also the charge-order superstructure resides within the NiO2 layers; the holes are mainly located on in-plane oxygens surrounding a Ni2+ site with the spins coupled antiparallel in close analogy to Zhang-Rice singlets in the cuprates.