Hard Disk Drive (HDD). The block of magnetic heads

The hard disk drive includes the following components – magnetic plates on which information is recorded, read/write heads, engines that make the plates rotate at high speed and also the electronics unit, which plays a big role in the performance of hard drives.

In this regard, the hard disk device can be divided into three blocks.

The first block is information storage consisting of one or several glass metal discs, covered on both sides with a magnetic layer, on which data is written. The magnetic surface of the disks is divided into concentric tracks, which in turn are divided into sectors. There is another division – cylinders. Cylinders are the sum of all the tracks that coincide with each other vertically, over all working surfaces.

The second block is the mechanical part, which is responsible for the rotation of the disks of the first block, as well as the precise positioning of the read/write heads. Each disk surface is assigned its own head and they are arranged vertically in an exact column. Thus, at any time, all the heads are on tracks with the same number and work within the same cylinder. As the technological parameters of the hard disk indicates the number of read heads, and not the number of working surfaces.

A hard disk magnetic head is a tiny object that “floats” at a very small distance above the magnetic surface of the disk. It is attached to the tip of the carrier and consists of two parts (invisible to the naked eye) – the reading head and the recording head.

The work of the reading head is to determine the changes in the magnetic flux that modulate the zero and one bits. The reading head is made of a magnetoresistive material – its electrical resistance varies as a function of the magnetic field passing through it. The recording head has a more complex structure, since it needs to create a magnetic field strong enough to change the orientation of the magnetic domains in the plate. For this task, one or more coils are used.

The size of the hard drive head is impressive. The width is less than a hundred nanometers, and the thickness is about ten. The head hovers above the plate, rotating at a speed of 15,000 rpm, at a height equivalent to 40 atoms. All elements of the head are made according to technologies similar to the production of microprocessors. That is, heads are cut from substrates on which they are formed by photolithography and deposition of the necessary materials. Thus, the production of magnetic heads is characteristic only of large companies, since The manufacture of magnetic heads requires significant financial and intellectual costs.

The third block is the electronics block, which includes the microcircuits responsible for data processing, the correction of possible errors and the management of mechanical memory, as well as the cache memory chips.