Role of Ce 4f hybridization in the origin of magnetism in nanoceria

TL;DR

This study reveals that hybridized Ce 4f and O 2p states, influenced by nanostructure and defects, are crucial for ferromagnetism in nanoceria, with foreign ions enhancing magnetic moments without altering vacancy orbitals.

Contribution

It demonstrates the role of Ce 4f hybridization and vacancy orbitals in nanoceria's ferromagnetism, highlighting the impact of defects and foreign ions.

Findings

Ce 4f and O 2p hybridized states are key to ferromagnetism.

Foreign ions increase magnetic moments at Ce 4f sites.

Vacancy orbitals remain unchanged despite ion doping.

Abstract

Nanoscale CeO2 (nanoceria) is a prototypical system that presents d0 ferromagnetism. Using a combination of x-ray absorption spectroscopy, x-ray magnetic circular dichroism and modelling, we show that nanostructure, defects and disorder, and non-stoichiometry create magnetically polarized Ce 4f and O 2p hybridized states captured by the vacancy orbitals (Vorb) that are vital to ferromagnetism. Further, we demonstrate that foreign ions (Fe and Co) enhance the moment at Ce 4f sites while the number of Vorb is unchanged, pointing clearly to the mechanism of orbital hybridization being key missing ingredient to understanding the unexpected ferromagnetism in many nanoscale dilute magnetic oxides and semiconductors.