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Conceptually, the read and
write head is very simple. The principal is based on electrical
theory seen in Chapter 0001. Specifically, applying electrical current
to a coil produces a magnetic field, which alters
the magnetic polarity on the magnetic substrate coated
on a platter. To read the magnetic polarity, electrical
current in the coil is modified when it passes
over the magnetic substrate.
Figure 53: Read/Write Heads
Hand Made Heads
In the early days, the read/write head was turned into a coil by human skilled labor. Specifically, it was done by silk weavers. They had the skills needed work with (by human standards) very small copper to wind the copper around the little V with 'wings', creating the read/write head. The 'wings' helped the head float on an air bearing, much like a kite. The spinning of the platters created the air bearing. Now you know why the insides of a hard drive must be free of contamination.
Giant MagnetoResistive (GMR)
IBM has pioneered new techniques in hard drives. The latest is Giant MagnetoResistive (GMR) heads, named from the giant magnetorestive effect. The effect comes from the fact that by working with different magnetic materials in thin layers, there is a large resistance to change when in a magnetic field. How GMR drives are manufactured is too complex a topic for this book. However if you have wondered how IBM could get a 1 Gig drive about the size of quarter, now you know.
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