Reading & writing data

Permanent magnets Each permanent magnet (naturally magnetic material) has a "north" and a "south" pole where north poles attract south poles and vice versa.

Voice coil Electricity circulated through the voice coil creates an electromagnet (a magnetic field produced by an electric current). Current flow direction through the coil changes the orientation of the north and south poles of the electromagnet, which moves the voice coil either toward or away from the north and south poles of the magnets. The intensity and duration of the current determine how quickly and how far the coil moves.

Voice coils move fast enough to pivot the arms from the outside to the inside of the platter (full stroke) over 50 times per second!

Ribbon The ribbon transports all information and electrical current between the logic board and actuator.

Arms The arms are connected and pivot together.

Read-write heads

platter surface

Sliders The disk-facing surface of the slider has specific shapes etched into it that manage air flow and pressurization. As the platters spin, an air pocket or “air bearing” is created and keeps the head ~2 nm (nanometer) from each platter – thinner than a finger print.

Read heads The read heads are TMR (tunneling magnetoresistance) devices, which consist of an insulator sandwiched between two sensitive magnetic materials Magnetic fields from the platter influence the closest magnet, causing electrons to tunnel or travel through the insulator and flip the polarity of the second magnet — thus, "reading" the platter's varying fields without disturbing them.

Write heads Write heads create an electromagnetic field that positions the north pole of a domain either up or down. The magnetic field is such that one side of it is much more concentrated, while the other end is more spread out. This allows the field to influence only the atoms on one side of the field (the “right side” of the field in this graphic). A magnetic domain with a north pole up could be a 1 while one with a north pole down could be a 0. Each 1 or 0 is considered a "bit" of data.

Magnetic domain Electrons in atoms create magnetic fields, and the direction they “spin” determines the direction of their north and south magnetic poles. Hard disk magnetic domains usually consist of about 100,000 atoms with magnetic poles oriented in the same direction.