Magneto-Optical Spectroscopy of Anatase TiO2 Doped with Co

TL;DR

This study investigates the magneto-optical properties of Co-doped anatase TiO2 at room temperature, revealing a strong magneto-optical response linked to Co content and carrier concentration, with implications for ferromagnetism in semiconductors.

Contribution

It demonstrates large magneto-optical effects in Co-doped TiO2 and suggests a link between Co impurities, carriers, and ferromagnetism, expanding understanding of magnetic semiconductors.

Findings

Large magneto-optical response observed across UV-visible spectrum.

Magneto-optical response increases with Co content and carrier concentration.

Peak magnetic circular dichroism of ~10400 degree/cm at 3.57 eV.

Abstract

Magneto-optical spectroscopy of a transparent ferromagnetic semiconductor, anatase TiO2 doped with Co, is carried out at room temperature. A large magneto-optical response with ferromagnetic field dependence is observed throughout from ultraviolet to visible range and increases with increasing Co content or carrier concentration. The magnitude of magnetic circular dichroism (MCD) per unit thickness has a peak around the absorption edge such a huge value of ~10400 degree/cm at 3.57 eV for a 10 mol% Co-doped specimen. Although the results are not sufficient to prove that the ferromagnetism is in the ordinary framework of diluted magnetic semiconductors, the coexistence of Co impurity and mobile carrier is shown to transform the band structure of host TiO2 to generate ferromagnetism.