There is a layer of magnetic material on the surface of the platters. Today a thin-film media is used here. Thin-film media is a microscopic layer of pure metal bonded to the substrate surface through an interim layer. Because the distance between head and platters is very small (about 10 micro inches), but they can not touch with each other. So the thin-film media is very flat and is coated with a protective layer to help survive head crashing.
- the arm and read and write head
The arm that holds the read/write heads is controlled by the mechanism in the upper-left corner, and is able to move the heads from the hub to the edge of the drive. The arm and its movement mechanism are extremely light and fast. The arm on a typical hard-disk drive can move from hub to edge and back up to 50 times per second. It is hard to believe. But it is the truth.
Simply, The read and write head is a ferromagnetic core. It can product a variety magnetic fields through a variety current to be able to write data onto the media in ASC2. And also can product variety current though inducing the variety magnetic field on the surface of the platter to read data from the hard disk drive.
Secondly, we should know how they work together.
Whenever reading or writing, the platters are rotated at a high speed. The head and the media never touch with each other. Even if they are working. Because a little touch can cause an immense damage of head and the media` surface. When they are working, read and write head are made to float above a platter surface by suspending the heads on a layer of moving air. Just like the airplane flying in the air. But the plane does not move, the air moves. Platter rotation creates a slight cushion that elevates the heads. That is why all hard drives seal their platter assemblies into an airtight chamber. The reason for such a seal is to prevent dust, dirt, spill or stands of hair. Once they land on a platter` s surface, it can easily result in a head crash. A head crash can damage the head, the media, or both, and physical damage can result in an unusable drive.
When you want to read data from the hard drive. First the heads move to the area where you put your data. And then the head can induce the variety magnetic fields and turn them into variety current and the variety current is translate into the ASC2 code , at last the code is sent to the CPU. The hard disk drive is done.
When you want to write the data on the media, the posses almost is the same. But the principle is opposite. This time the hard drive receive the code from the CPU and translate it into variety current and the variety current product variety magnetic fields though the read and write head to made the media magnetic.
What careers are related to the use of the technology?
Electronic design engineer: the engineer can design better read and write head for the hard drive.
Structural engineer: the platter run very fast so a good structure for the hard drive is very important.
Mechanical engineer: the motor need improve endlessly with the higher rotation of the platter. The more advanced axletree should be found, which can produce less heat.
Material engineer: find better magnetic material for the hard drive. Make the thin-film media technology more mature.
Aerostatic engineer: calculate the air flow in the hard drive. Make the arm be right height up the platter when the platter is at different speed.