Editing Disk read-and-write head (section)

=== Traditional head ===
The heads themselves started out similar to the heads in [[tape recorder]]s—simple devices made out of a tiny C-shaped piece of highly magnetizable material such as [[permalloy]] or [[ferrite (magnet)|ferrite]] wrapped in a fine wire coil.  When writing, the coil is energized, a strong [[magnetic field]] forms in the gap of the C, and the recording surface adjacent to the gap is magnetized.  When reading, the magnetized material rotates past the heads, the [[magnetic core|ferrite core]] concentrates the field, and a [[current (electricity)|current]] is generated in the coil. In the gap the field is very strong and quite narrow.  That gap is roughly equal to the thickness of the magnetic media on the recording surface.  The gap determines the minimum size of a recorded area on the disk.  Ferrite heads are large, and write fairly large features.  They must also be flown fairly far from the surface thus requiring stronger fields and larger heads.<ref name=":0">{{Cite web|url=https://www.tomshardware.com/reviews/hard-drive-magnetic-storage-hdd,3005-2.html|title=Read/Write Head Designs: Ferrite, Metal-In-Gap, And Thin-Film - Hard Drives 101: Magnetic Storage|date=2011-08-30|website=Tom's Hardware|language=en|access-date=2019-04-13}}</ref>