page_title: Chromium(IV) oxide
section_title: Uses
hierarchical_section_title: Chromium(IV) oxide / Uses
caption_attribution_description: English: Cassette tape, coated with chromium dioxide (CrO2). Cr4+ is dark brown to black.
context_page_description: Chromium dioxide or chromium(IV) oxide is an inorganic compound with the formula CrO₂. It is a black synthetic magnetic solid. It once was widely used in magnetic tape emulsion. With the increasing popularity of CDs and DVDs, the use of chromium(IV) oxide has declined. However, it is still used in data tape applications for enterprise-class storage systems. It is still considered by many oxide and tape manufacturers to have been one of the best magnetic recording particulates ever invented.
context_section_description: The crystal's magnetic properties, derived from its ideal shape such as anisotropy which imparted high coercivity and remanent magnetization intensities, resulted in exceptional stability and efficiency for short wavelengths, and it almost immediately appeared in high performance audio tape used in audio cassette for which treble response and hiss were always problems. Unlike the imperfectly formed ferric oxide coating commonly used, the chromium dioxide crystals were perfectly formed and could be evenly and densely dispersed in a magnetic coating leading to hisher signal/ratios in audio recordings. Chrome tapes did, however, require audio cassette recorders to be equipped with a higher bias current capability (roughly 50% greater) than that used by ferric oxide to properly magnetize the tape particles. Also introduced was a new equalization (70 μs) that traded some of the extended high-frequency response for lower noise resulting in a 5–6 dB improvement in signal-to-noise ratio over ferric-oxide audio tapes. These bias and EQ settings were later carried over to "chrome-equivalent" cobalt-modified tapes introduced in the mid-1970s by TDK, Maxell, and others. Later research significantly increased the coercivity of the particle by doping or adsorbing rare elements such as iridium onto the crystal matrix or by improving the axial length-to-deprecated ratios. The resulting product was potentially a competitor to metallic iron pigments but apparently achieved little market penetration.
caption: CrO2 cassette tape
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