X-ray spectromicroscopy of single NiO antiferromagnetic nanoparticles

The chemical and magnetic properties of NiO nanoparticles (NP) have been studied with single-particle sensitivity by means of synchrotron-based, polarization-dependent X-ray absorption spectroscopy using photoemission electron microscopy around the Ni L3,2 edges. Three samples of NP in a size range of 40-120 nm were synthesized by thermal decomposition and subsequent calcination processes. The analysis of the local X-ray absorption spectra of tens of individual NP indicates a strong dependence of their Ni oxidation state with the calcination protocol of each sample. Additional electron-microscopy-based images and spectra of a few individual NP as well as other standard macroscopic data are in very good agreement with these experimental findings. These results showcase the relevance of combining standard and advanced single-particle studies to gain further insight into the understanding and control of electronic and magnetic phenomena at the nanoscale. © A. I. Figueroa, C. Moya, M. X. Aribó, J. Ara, M. García del Muro, A. Kleibert, S. Valencia, A. Labarta, X. Batlle, and A. Fraile Rodríguez, 2024.