magnetic head
Magnetic heads are small toroidal magnets with which analogsignals or digital data can be written to, erased from, and read again from a magnetizable medium. Magnetic heads are the read/write heads for magnetic tapes, magnetic strips, diskettes or hard disks.
In tape recorders, the read/write heads are stationary or rotating magnetic heads with toroidal cores that induce a magnetic field in the tape material via a small air gap. The size of the air gap is between 5 µm and 10 µm and, in conjunction with the tape speed and the tape material, is responsible for the storable frequency and, in the case of data storage, for the storable data rate.
To keep wear on the tape material as low as possible, the magnetic tape is fed past the magnetic head at a small distance via an air cushion. Tape drives have separate magnetic heads for storing and reading as well as for erasing, next to the read/write heads the erase head. Multitrack systems have a separate magnetic head for each track, shielded from the others.
Unlike tape materials, which should have high remanence so that the residual induction is as high as possible, magnetic heads should have no or negligible remanence. Therefore, magnetic heads are made of soft magnetic materials, ferrites or alloys known as Alfenol and Vacudor.