Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2000-09-25
2003-07-08
Neyzari, Ali (Department: 2655)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C428S690000
Reexamination Certificate
active
06590836
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to magneto optical recording media recording a signal through a laser beam and a magnetic field.
DESCRIPTION OF THE BACKGROUND ART
Magneto optical recording media are noted as a recording medium which is rewritable, large in storage capacity and highly reliable and they are increasingly put to practical use as computer memory and the like. Furthermore, a magneto optical recording medium having a recording density of 4.6 Gbits/inch
2
has been recently standardized as the Advanced Storaged Magneto Optical disk (AS-MO) standard and is about to be put to practical use.
Furthermore, there has also been proposed a magneto optical recording medium having a recording capacity of 14 Gbytes in a system transferring a magnetic domain of a recording layer to a reproduction layer and enlarging the magnetic domain in the reproduction layer and thus reproducing a signal.
In this system, a signal recorded in the magneto optical recording medium is reproduced by directing a laser beam to apply an alternate magnetic field of approximately ±3000 Oe to transfer each recording domain of the recording layer to the reproduction layer and enlarge the domain in the reproduction layer to reproduce the signal.
In fabricating a conventional magneto optical recording medium having a structure of substrate /SiN/GdFeCo/SiN/TbFeCo, SiN, GdFeCo, SiN and TbFeCo are successively sputtered on the substrate. As such, when GdFeCo corresponding to a reproduction layer is provided, SiN has already been provided on the substrate. Since GdFeCo, SiN, TbFeCo are sputtered for example in a plasma of argon gas, while GdFeCo is being provided ions of various species in the plasma etch a portion of SiN and GdFeCo takes Si, N and the like therein to. Consequently, the GdFeCo obtained would have a Gd content smaller than a set value and the reproduction layer would have a degraded characteristic.
More specifically, because of a degraded characteristic at an interface of the reproduction layer of GdFeCo layer and another layer, a degraded perpendicular magnetic anisotropy in particular, when a leaking magnetic field extends from the recording layer through a non-magnetic layer and reaches the reproduction layer the reproduction layer's magnetization is not inverted in the same direction as the recording layer's magnetization and a signal can thus not be reproduced accurately.
Furthermore, the plasma's negative effect on GdFeCo also occurs after GdFeCo is provided when SiN is provided. More specifically, when GdFeCo is provided and SiN is then provided, Si, N and the like are disadvantageously introduced through the plasma into GdFeCo. Thus the reproduction layer also would have a degraded characteristic and a signal can thus not be reproduced accurately.
SUMMARY OF THE INVENTION
The present invention therefore contemplates a magneto optical recording medium having a non-magnetic layer formed in contact with a reproduction layer, capable of preventing the non-magnetic layer from affecting the reproduction layer and thus preventing the reproduction layer from having a degraded characteristic.
The present invention provides a magneto optical recording medium including a dielectric layer, a reproduction layer formed in contact with the dielectric layer, a non-magnetic layer formed in contact with the reproduction layer, and a recording layer formed in contact with the non-magnetic layer, the reproduction layer including a first layer corresponding to a rare earth metal layer, a second layer corresponding to an alloy layer of rare earth metal and transition metal formed in contact with the first layer, and a third layer corresponding to a rare earth metal layer formed in contact with the second layer.
In the present magneto optical recording medium the first and second layers can prevent an impurity existing in the dielectric layer and the non-magnetic layer, each arranged on one of opposite sides of the reproduction layer, from entering the alloy layer of rare earth metal and transition metal when the recording medium is being fabricated. As such the present invention can prevent the non-magnetic layer from affecting the reproduction layer and thus prevent the reproduction layer from having a degraded characteristic.
Furthermore the present invention provides a magneto optical recording medium including a dielectric layer, a reproduction layer formed in contact with the dielectric layer, a non-magnetic layer formed in contact with the reproduction layer, and a recording layer formed in contact with the non-magnetic layer, the reproduction layer including a first layer corresponding to a rare earth metal layer formed in contact with the dielectric layer, and a second layer corresponding to an alloy layer of rare earth metal and transition metal.
In the present magneto optical recording medium the first layer can prevent an impurity in the dielectric layer from entering the alloy layer of rare earth metal and transition metal when the recording medium is being fabricated. As such the present invention can prevent the non-magnetic layer from affecting the reproduction layer and thus prevent the reproduction layer from having a degraded characteristic.
Furthermore the present invention provides a magneto optical recording medium including a reproduction layer, a non-magnetic layer formed in contact with the reproduction layer, and a recording layer formed in contact with the non-magnetic layer, the reproduction layer being formed of a first layer corresponding to an alloy layer of rare earth metal and transition metal and a second layer corresponding to a rare earth metal layer formed in contact with the non-magnetic layer.
In the present magneto optical recording medium the second layer can prevent an impurity in the non-magnetic layer from entering the alloy layer of rare earth metal and transition metal when the recording medium is being fabricated. As such the present invention can prevent the non-magnetic layer from affecting the reproduction layer and thus prevent the reproduction layer from having a degraded characteristic.
Preferably, the rare earth metal layer is a Gd layer and the rare earth metal forming the alloy layer is Gd.
Thus the Gd layer can prevent an impurity in the non-magnetic layer from entering the alloy layer of rare earth metal and transition metal when the magneto optical recording medium is being fabricated. As such in the present invention the Gd typically used as a rare earth metal forming a reproduction layer can prevent the reproduction layer from having a degraded characteristic.
Furthermore the present invention provides a magneto optical recording medium including a dielectric layer, a reproduction layer formed in contact with the dielectric layer, a non-magnetic layer formed in contact with the reproduction layer, and a recording layer formed in contact with the non-magnetic layer, wherein the reproduction layer is an alloy layer of rare earth metal and transition metal and contains more of the rare earth metal at a portion thereof closer to the dielectric layer and a portion thereof closer to the non-magnetic layer.
In the present magneto optical recording medium any impurity entering from the non-magnetic layer to the reproduction layer can be held in the reproduction layer at an area containing a large amount of rare earth metal. As such the present invention can prevent the non-magnetic layer from affecting the reproduction layer and thus prevent the reproduction layer from having a degraded characteristic.
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Ishida Hiroki
Noguchi Hitoshi
Yamaguchi Atsushi
Armstrong Westerman & Hattori, LLP.
Neyzari Ali
Sanyo Electric Co,. Ltd.
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