Abstract The electromagnetic coil (5) for applying a magnetic bias field (8) to the recording bit (1-1) of a magnetooptical recording disk apparatus is provided with a yoke (7) made of soft magnetic material, such as soft iron. The yoke (7) surrounds the coil's (5) outer round side (51) as well as the coil's flat side (52) opposite from the disk (1) side. The light beam (21) or the optical system is arranged in an opening of the yoke (7) on the coil's (5) flat side (52). The yoke (7) reduces the magnetic resistance of the coil (5), thus increases the magnetic field intensity at the recording bit (1-1) which requires a magnetic field intensity over a certain level. Consequently, the required magnetic field intensity is achieved with less coil (5) current, in other words, within a reasonable range of the coil's (5) temperature rise.
A magneto-optical recording disk apparatus having: a recording disk (1) having a perpendicular magnetic anisotropic material (11) thereon; an electromagnetic bias coil (5) for applying a magnetic field to a recording bit (1-1) of said perpendicular magnetic anisotropic material (11), the magnetic field (8) being perpendicular to the surface of the recording disk (1); and an optical system for focusing a light beam (21) onto the recording bit (1-1), the optical system being located on the same side of the recording disk (1) as the electromagnetic bias coil (5) and being coaxial with the electromagnetic bias coil (5), characterized by a magnetic yoke (7), made of a soft magnetic material, surrounding the coil's (5) outer round side (51) as well as the coil's (5) flat side (52) opposite to the recording disk (1), said flat side portion (72) of said yoke (7) having an opening through which the optical system is arranged, whereby the current through the electromagnetic coil (7) necessary to produce the magnetic field (8) to the recording bit (1-1) is reduced.
Claim 2
Dependent Claim
174 words
A magneto-optical recording disk apparatus having: a recording disk (1) having a perpendicular magnetic anisotropic material (11) thereon; an electromagnetic bias coil (5) for applying a magnetic field to a recording bit (1-1) of said perpendicular magnetic anisotropic material (11), the magnetic field (8) being perpendicular to the surface of the recording disk (1); and an optical system for focusing a light beam (21) onto the recording bit (1-1), the optical system being located on the same side of the recording disk (1) as the electromagnetic bias coil (5) and being coaxial with the electromagnetic bias coil (5), characterized by a magnetic yoke (7), made of a soft magnetic material, surrounding the coil's (5) outer round side (51) as well as the coil's (5) flat side (52) opposite to the recording disk (1), said flat side portion (72) of said yoke (7) having an opening through which the optical system is arranged, whereby the current through the electromagnetic coil (7) necessary to produce the magnetic field (8) to the recording bit (1-1) is reduced.
Claim 3
Dependent Claim
25 words
An apparatus of claim 1, characterized in that said soft magnetic material is chosen from a group of soft iron, silicon steel and soft ferrite.
Claim 4
Dependent Claim
34 words
An apparatus of claim 1 or 2, characterized in that a set consisting of the electromagnetic bias coil (5) comprising said magnetic yoke (7) is provided at one side of the recording disk (1).
Claim 5
Dependent Claim
36 words
An apparatus of claim 1 or 2, characterized in that two sets each consisting of an electromagnetic bias coil (5) comprising said magnetic yoke (7) are provided in symmetry with respect to the recording disk (1).
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