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| Home > Publications database > Crystal field and spin fluctuation in heavily dopednickelates |
| Poster (Invited) | FZJ-2026-04489 |
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2026
Abstract: Hole-doped nickelates, isostructural to cuprates, are a strongly correlated electron system thatexhibits charge order as well as peculiar spin dynamics associated with the doping level. The holedoping can be made with introduction of cations like Sr (quenched disorder), by oxygen overstoichiometry(annealed disorder) or both. The interest in focusing on O doped samples is the uniquecoexistence of 3D modulated spin and oxygen ordering. Such coexistence might support the pictureof pinning the magnetic to the oxygen order in oxygen-doped samples. This would also imply that thequasi-2D nature of the spin correlations might not be the optimal model for heavily oxygen-dopednickelates.In this study we present the latest result of our triple axis neutron spectroscopy investigation ofcrystal field and spin order and dynamics in A2NiO4+d samples (with A=Nd,Pr, d=0.25 or 0.23). Thespin fluctuations were followed along the layers’ plane, as well as out of plane and both revealed anevident dispersion with corresponding coupling strength much closer that what found at lower doping.The analysis in function of temperature also highlighted a marked difference between the onset of spinfluctuations and spin order as well as their intensity evolution. Crystal field analysis showed also aclear dependence of the energy of first CEF transition with respect to the O content (Figure 1) [1]. Thestrongly oxygen doped phase, bringing (ordered) interstitial oxygen in between NiO planes influencesthe 3D magnetic order, as well as CEF levels, and lattice order and dynamics [2]. The overall scenarioseems supporting the picture of pinning the magnetic to the oxygen order in oxygen-doped samples.Figure 1: Trend of first CEF level energy obtained through point charge model calculationsby varying the atomic positions of Oap. From [1]References[1] L Z Cunha et al., J Phys Conf Series 3161 012020, 2026 ; [2] A. Perrichon et al., Phys Rev B 107, 144303, 2023
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