Magnetic Ordering in Sr3YCo4O10+x.

Takayoshi Kishida,Brian C Sales,Jiaqiang Yan,Myron D Kapetanakis,Matthew F Chisholm,Stephen J Pennycook,Sokrates T Pantelides

doi:10.1038/srep19762

Abstract

Transition-metal oxides often exhibit complex magnetic behavior due to the strong interplay between atomic-structure, electronic and magnetic degrees of freedom. Cobaltates, especially, exhibit complex behavior because of cobalt’s ability to adopt various valence and spin state configurations. The case of the oxygen-deficient perovskite Sr3YCo4O10+x (SYCO) has attracted considerable attention because of persisting uncertainties about its structure and the origin of the observed room temperature ferromagnetism. Here we report a combined investigation of SYCO using aberration-corrected scanning transmission electron microscopy and density functional theory calculations. Guided by theoretical results on Co-O distances projected on different planes, the atomic-scale images of several different orientations, especially of the fully oxygenated planes, allow the unambiguous extraction of the underlying structure. The calculated magnetic properties of the new structure are in excellent agreement with the experimental data.

Highlights

Transition-metal oxides often exhibit complex magnetic behavior due to the strong interplay between atomic-structure, electronic and magnetic degrees of freedom
We report a combined investigation of SYCO using aberration-corrected scanning transmission electron microscopy and density functional theory calculations
Atomic resolution imaging by scanning transmission electron microscopy (STEM) can be routinely performed using the high-angle annular dark field (HAADF) mode of imaging

Summary

Results and Discussion

These shapes originate from atomic arrangements along the columns that are too small to be resolved (as separated features) but are large enough to make the feature non-circular. When viewed along the [110]p and[110]p directions, the Co columns in the fully oxygenated layer of our model structure are predicted to alternate between the HS and IS state (Fig. 4b,c). We find, in the ABF-STEM images, periodic variations in Co-O bond lengths in the fully oxygenated Co-O layers arising from these alternating high spin and intermediate spin Co atoms

Methods

Author Contributions

Additional Information