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This layer is called the protective layer because it protects the disk from damage caused by accidental contact from the heads, “head crash” or other foreign material from entering the drive On the top of the magnetic media, is applied a super-thin, protective, lubricating layer. Another such method is electroplating, using a process similar to that used in electroplating jewelry. A thin coating is deposited on both sides of the substrate, mostly by vacuum deposition process called magnetron sputtering. Special techniques are employed for the deposition of magnetic material on the substrate material. Its thickness is only a few millionths of an inch. The media layer is a thin coating of magnetic material applied to the surface of the platters and where the actual data is stored. The substrate material forms the base upon which actual recording media is deposited. Glass platters are replacing aluminium platters because they provide improved rigidity, better quality, thinner platters, and thermal stability. For this reason demand for alternatives on the platter material are increasing. However, as technology advances, the gap between heads and platters is decreasing and the speed that the platters spin at is increasing. Earlier, since the gap between the heads and the platter was relatively high, the platter surface being smooth and flat was less of an issue. This alloy is rigid, lightweight, stable, inexpensive, easy to work with and is readily available. The most commonly used material for making this physical layer is an Aluminium alloy. The substrate has no specific function but to support the media layer. The bulk material of which platters are made up, forms the base on which media layer is deposited. This complex three layered media is discussed in detail as follows: When the magnetic media is applied to the surface of the substrate material, a thin lubricating layer is applied to protect the material. This, thin coating where actual data is stored is the media layer. On both sides of the substrate material, a thin coating is deposited by a special manufacturing technique. The platter has a core made up of aluminium or glass substrate, covered with a thin layer of Ferric oxide or cobalt alloy.
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Several platters are mounted on a fixed spindle motor to create more data storage surfaces in a smaller area. Platter is a circular, metal disk that is mounted inside a hard disk drive. In this way, the drive heads can reach the entire surface of each platter. As the platters spin, the drive heads move in toward the center surface and out toward the edge. Electromagnetic read/write heads are positioned above and below each platter.