Magnetic writing head for magneto-optical recording with thick protective coating

DETAILED DESCRIPTION According to the invention, the magnetic head is produced on a silicon substrate, which makes it possible to use microelectronics technology and in particular a collective production, whilst bringing about a good dissipation of the heat given off by the coil.
This coil is constituted by one or more conductor levels spirally wound by at least ten turns, each turn being located in a plane parallel to the substrate.
The resulting coil with an internal radius of approximately 20 to 100 .
mu.
m and an external radius of approximately 100 .
mu.
m to 1 mm, makes it possible to create on its axis a magnetic field with a significant perpendicular component.
A magnetic circuit can assist the amplification of this writing field.
This magnetic circuit can be limited to a thin magnetic film with a uniform thickness (approximately 4 .
mu.
m), which can be very easily produced in microelectronics technology.
In the aforementioned EP-A-492 888, the magnetic pole also helps to increase the field in the centre of the head, but the simulation results obtained by the applicant show that the influence of said pole at a considerable distance becomes negligible and that it is preferable to limit to a constant thickness magnetic sheet (e.
g.
of FeNi or Sendust).
This gives a simpler production process with better performance characteristics, which are almost as good for a head moving at a significant distance from the disk (approximately 5 .
mu.
m).
As the head according to the invention is intended to operate with very short times, i.
e.
at high frequency (up to several dozen MHz), induced currents may appear in the magnetic circuit.
These currents can have a detrimental effect on the useful magnetic field created by the head.
They can be eliminated by making in particular radial slots or grooves in the plane of the disk.
These grooves completely traverse the magnetic circuit and subdivide the latter into electrically isolated sectors without disturbing the passage of the magnetic field.
The electrical connections can be made through the silicon substrate (intraconnections)