Signature of Carrier-Induced Ferromagnetism in Ti_{1-x}Co_{x}O_{2-delta}: Exchange Interaction Between High-Spin Co 2+ and the Ti 3d Conduction Band

TL;DR

This study uses X-ray photoemission spectroscopy to show that high-spin Co 2+ ions in Ti_{1-x}Co_{x}O_{2-delta} induce ferromagnetism through exchange interactions with the Ti 3d conduction band, indicating intrinsic ferromagnetism.

Contribution

It provides direct spectroscopic evidence linking high-spin Co 2+ states and carrier hybridization to intrinsic ferromagnetism in Ti_{1-x}Co_{x}O_{2-delta}.

Findings

Co ions are high-spin Co 2+ in the material.

Strong hybridization between Co 3d and Ti 3d states.

Room temperature ferromagnetism is intrinsic.

Abstract

X-ray photoemission spectroscopy measurements were performed on thin-film samples of rutile Ti_{1-x}Co_{x}O_{2-delta} to reveal the electronic structure. The Co 2p core level spectra indicate that the Co ions take the high-spin Co 2+ configuration, consistent with substitution on the Ti site. The high spin state and the shift due to the exchange splitting of the conduction band suggest strong hybridization between carriers in the Ti 3d t2g band and the t2g states of the high-spin Co 2+. These observations support the argument that room temperature ferromagnetism in Ti_{1-x}Co_{x}O_{2-delta} is intrinsic.