Oxygen-defect-induced magnetism to 880 K in semiconducting anatase TiO_2−δfilms

TLDR

The study demonstrates TiO₂₋δ as a semiconducting material exhibiting ferromagnetism up to 880 K without magnetic ions. Magnetism arises from controlled anion defects introduced at the film–substrate interface and during oxygen‑deficient processing. The material shows n‑type carriers (~3 × 10¹⁷ cm⁻³), a spin density of ~10²¹ cm⁻³, and ferromagnetism up to 880 K that scales with conductivity, indicating a double‑exchange mechanism and offering a new route for spintronic semiconductors.

Abstract

We demonstrate a semiconducting material, TiO2−δ, with ferromagnetism up to 880 K, without the introduction of magnetic ions. The magnetism in these films stems from the controlled introduction of anion defects from both the film–substrate interface as well as processing under an oxygen-deficient atmosphere. The room-temperature carriers are n-type with n∼3 × 1017 cm−3. The density of spins is ∼1021 cm−3. Magnetism scales with conductivity, suggesting that a double exchange interaction is active. This represents a new approach in the design and refinement of magnetic semiconductor materials for spintronics device applications.