Room-Temperature Ferromagnetism in Transparent Transition Metal-Doped Titanium Dioxide

TLDR

Dilute magnetic semiconductors and wide‑gap oxide semiconductors are promising materials for magneto‑optical devices. Using a combinatorial screening of transition‑metal solubility and magnetic properties in TiO₂, the authors discovered transparent ferromagnetism in cobalt‑doped anatase thin films containing 0–8 % Co. Magnetic‑microscopy imaging shows ferromagnetic domain structure, the films remain ferromagnetic above room temperature with 0.32 μB per Co atom, and they are conductive with a 60 % positive magnetoresistance at 2 K.

Abstract

Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films with theconcentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the existence of ferromagnetic long-range ordering. The materials remain ferromagnetic above room temperature with a magnetic moment of 0.32 Bohr magnetons per cobalt atom. The film is conductive and exhibits a positive magnetoresistance of 60% at 2 kelvin.