Chromdioxid

Chromium dioxide, CrO2, also known as chromdioxide, is an inorganic compound in which chromium is in the +4 oxidation state coordinated to oxide. It crystallizes in a rutile-type structure and is typically produced as a black to brown-black solid. CrO2 is notable for its combination of ferromagnetism and metallic electrical conductivity, properties that give it a high spin polarization and classify it as a half-metal in some descriptions.

In terms of physical properties, chromium dioxide exhibits ferromagnetic order with a Curie temperature around 380 to 390 kelvin. It shows relatively high magnetic remanence and coercivity for an oxide and conducts electricity through the chromium 3d states. The rutile crystal framework provides anisotropic magnetic and electronic behavior, which has attracted interest in fundamental studies of magnetism and spintronics.

Historically, CrO2 gained prominence as the magnetic material used in many magnetic tapes for audio and video recording during the 1960s to 1980s, valued for its strong magnetic signal and stability. With advances in recording media and alternatives such as metal particle and ferrite formulations, the industrial use of CrO2 has declined, though it remains a subject of research for magnetic and spintronic applications.

Chromium dioxide is not known as a natural mineral and is produced synthetically. Like other chromium compounds, CrO2 can pose health and environmental risks, as chromium(IV) species are toxic. Safe handling requires appropriate containment, ventilation, and disposal in accordance with applicable regulations.