The recording of data onto the hard disc

The recording of data onto the hard disc The working principle of the hard disc is similar to that of the tape recorder. The working surface of the disc is moving versus the reading head (like the inductance coil with the gap within the magnetic wire). As the alternate electric current is supplied to the coil of the head (during the recording), the appearing alternate magnetic field from the gap affects the ferromagnetic surface of the disc and alters the direction of the domain magnetization depending on the intensity of the signal. During the reading the shift of the domains at the head gap the magnetic current within the magnetic ire of the head alters, which leads to the appearance of the alternate electric signal within the coil due to the electromagnetic induction effect. Among the recording technologies the ones applied for serial models and the experimental ones may be distinguished. Let us consider the serial ones first. The method of longitudinal recording, when the data bits are being recorded with a small head, which magnetizes billions of discrete areas-domains passing over the rotating surface of the disc. The magnetization vector of the domain is longitudinal, that is parallel to the surface of the disc. Each of the areas is logically one or zero depending on the magnetization. The maximum density of recording, available with this method, is 23 Gbit/cm2. In the present time gradual exclusion of the method by the more progressive methods is taking place. Here is one of them. The method of perpendicular recording, when the bits of information are saved in the vertical domains. This allows using more powerful magnetic fields and lessen the area of material, needed for recoding 1 bit of data. The recording density of the modern specimens exceeds 60 Gbit/ cm2. The hard discs with perpendicular recording are available on the market since 2005. The main distinction between these technologies is the direction of the domain magnetization - for the parallel recording it is parallel to the disc surface and for the perpendicular recording it is perpendicular. The higher density of the perpendicular recording is caused by the power of interaction between neighboring cells, not the internal characteristics within one domain. Among the experimental types of recording the following ones may be distinguished. The method of heat magnetic recording or the thermal assisted ...

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