A magnetic ribbon's surface is covered with magnetic particles. We have already seen how the latter dispose themselves depending upon the direction dictated by the magnetic field generated by the recording head. We also saw how this orientation brings about a magnetic field which is then transformed into an electric signal by the reproduction head. The particles' characteristics are an essential parameter when evaluating the quality of a magnetic ribbon. The principle is that the smaller the particles, the more accurate the reproduction of the recorded waveform.
The shape of the particles is also an important parameter: particles with a very irregular shape remain more separated one from another leaving empty surface space. This results in an increase in background hiss. Lets now take a look at the materials used to engender these particles and their characteristics.
- Iron Oxide (FeO2)
particles made up of this material are among the biggest (0.7 μm) and have a very irregular shape. As already mentioned, this means hiss.
- Chromium Dioxide (CrO2)
these particles are slightly smaller than the Iron Oxide particles but have a more regular shape and therefore allow for a higher density of the particles. This also means a far better reaction to high frequencies.
Very small particles (0.2 μm). This means great accuracy, even though a greater magnetic field is required to magnetize the ribbon.