A new high coercive magnetic particle for recording tape

A high coercive magnetic particle named AVILYN has been developed. This new particle is an acicular magnetic iron oxide on whose surface certain cobalt compounds have been adsorbed. The coercive force of the particles is determined by the amount of cobalt and other preparing conditions, and is controllable between 450 and 800 Oe. The particles display much improved thermal stability with respect to remanence and coercive force. The new video tape having a coercive force of 550 Oe is compatible with CrO
2
video tape in recording characteristics according to our measurement on a conventional VTR. The head wear rate of the tape is about one-fifth that of CrO
2
tape, and is almost the same as for conventional iron oxide tape. Tape demagnetization is not as serious as is in the case of cobalt-doped γ-Fe
2
O
3
tapes.