Cobalt-Substituted γ-Fe2O3 as a High-Density Recording Tape

In this study we investigated the recording performance of a surface composed of Co-substituted γ-Fe₂O₃ particles. These particles were cubic in shape with edge length of 500 to 1000 Å, and coercivity of 500 to 600 Oe. This high coercivity is due primarily to the large magnetocrystalline anisotropy of the cobalt cation in the spinel lattice. The recording surface exhibited higher output, better dynamic range, and considerably smaller half-pulse width than typical acicular γ-Fe₂O₃ surfaces. Coercivity and squareness were found to decrease dramatically with increasing temperature, and with adverse consequences affecting recording performance. Heating a prerecorded tape to 150°C results in a 50 percent loss of signal; the conventional γ-Fe₂O₃ tapes experience no loss.