CrO2s

CrO2 is chromium(IV) oxide, a binary oxide of chromium with oxidation state +4. It is best known for its metallic conductivity and ferromagnetism, making it unique among oxides. It exists in a rutile-type tetragonal crystal structure and has a high Curie temperature above room temperature, typically cited around 386–395 K. Its electronic structure gives high spin polarization at the Fermi level, leading to potential spintronic applications, though practical use is limited by chemical instability and challenges in large-scale, uniform synthesis.

Natural occurrence of CrO2 is rare; it is typically prepared synthetically, often via controlled oxidation of chromium(III) precursors or through deposition methods. It is sensitive to oxidation and moisture; in air, it can convert to chromium oxide(III) (Cr2O3) under certain conditions, necessitating protective measures.

Historically, CrO2 was widely used as a magnetic recording medium in magnetic tapes because of its high remanent magnetization and conductivity, but the development of alternative materials and environmental concerns reduced its prominence. In modern research, CrO2 is studied for spintronic and magnetic applications, including as a half-metallic electrode candidate, with doped or nanostructured forms explored to tailor properties.

Safety: Chromium compounds are toxic; handling CrO2 requires appropriate safety measures to avoid inhalation and dermal exposure. As with other chromium oxides, regulatory and health considerations guide its use and handling.