New duplication method by plating for magnetic recordings

It has been discovered that a ferromagnetic film plated in a constant magnetic field, much smaller than the coercive force of the film, is magnetized in the same direction as the applied magnetic field. It is considered that the magnetization of the film is fixed when the plated particles grow from a superparamagnetic state to a ferromagnetic state. A new duplication method for magnetic recordings is proposed as an application of this phenomenon. The method may be utilized to make master tapes with high coercive force by means of duplication from ordinary magnetic tapes with low coercive force. Considerable studies have been made on metallic films for high density recording in the past several years. The films are in most cases prepared by electrolytic or electroless deposition and vacuum evaporation [1,2]. Co-(P) or Co-Ni-(P) films are used to some extent on magnetic drums and disks. Magnetic properties such as induced anisotropies have been investigated for these ferromagnetic films prepared in a magnetic field [3]. In the present study it has been discovered that a ferromagnetic film deposited in a constant magnetic field, much smaller than the coercive force of the film, is magnetized in the same direction as the applied field. A new duplication method is proposed as an application of this phenomenon. An anhysteretic duplication is usually used for contact printing of magnetic tape recordings [4]. The signal is transferred when a master tape contacts a slave tape in an alternate magnetic field. However, master signals must be recorded with a special machine and copies may be made only on tapes with lower coercive force. A feature of the present method is that duplication is possible from low coercivity tapes to high coercivity tapes. In this paper the magnetization mechanism of the ferromagnetic films electrodeposited in a magnetic field was investigated and several duplication characteristics were measured for audio signals.