Read/Write Heads

- Sebastian Evers

Read/write heads are the tiny electromagnetic parts at the head of the mechanical swivel arm inside a hard disk drive. They are floating on a very small air cushion at the nanolevel above the ferromagnetic data layer when the magnetic disks are in rotation. The rotation speed of mechanical hard drives varies between 5.400 and 15.000 rpm (revolutions per minute).

There are two „heads“ per endcarriage, one for the writing and one for the reading process. During the writing access a magnetic field forms and changes the orientation of the individually writeable areas of the ferrit layer and thanks to remanence (remaining magnetism) they stay in this orientation permanently. This information is retrieved as induced voltage during the reading access. The number of read/write heads is dependent on the number of writeable magnetic surfaces.

Ongoing development makes it possible that the write/read units are able to work finely and densely and therefore enable accordingly high capacities (keyword: Heat-assisted magnetic recording (HAMR)).