Magnetooptical recording medium on which high-density information can be recorded and method of reproducing the recorded information

A magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising:

• a first magnetic layer;
• a second magnetic layer having a Curie temperature that is lower than that of said first magnetic layer;
• a third magnetic layer for storing information having a Curie temperature that is higher than that of said second magnetic layer, wherein the perpendicular magnetic anisotropy of said first magnetic layer is smaller than that of said third magnetic layer;
• and
• means between information tracks for substantially disconnecting each information track.

A magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising:

• a substrate;
• a first magnetic layer;
• a second magnetic layer having a Curie temperature that is lower than that of said first magnetic layer;
• a third magnetic layer for storing information, having a Curie temperature that is higher than that of said second magnetic layer;
• and
• a fourth magnetic layer, whose Curie temperature is higher than that of said second magnetic layer and lower than that of said first magnetic layer,
• wherein said first magnetic layer, said fourth magnetic layer, said second magnetic layer and said third magnetic layer are laminated on said substrate in that order, the perpendicular magnetic anisotropy of each of said first and fourth magnetic layers is smaller than that of said third magnetic layer, and exchange coupling is substantially disconnected between each of the information tracks.

An information reproducing method for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and exchange coupling is substantially disconnected between each of the information tracks, said method comprising the steps of:

• rotating the medium;
• projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• moving a domain wall in the first magnetic layer which comes into the region of temperatures when the medium rotates toward a side having higher temperature in the temperature gradient in the first magnetic layer;
• and
• reproducing the information by detecting rays of the light beam.

An information reproducing method for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and between each of the information tracks, a non-magnetic layer or an in-plane magnetic film exists, said method comprising the steps of:

• rotating the medium;
• projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• moving a domain wall in the first magnetic layer which comes into the region of temperatures when the medium rotates toward a side having a higher temperature in the temperature gradient in the first magnetic layer;
• and
• reproducing the information by detecting reflected rays of the light beam.

An information reproducing method for reproducing information from a magnetooptical recording medium comprising a substrate, a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, a third magnetic layer for storing information, having a Curie temperature that is higher than that of the second magnetic layer, and a fourth magnetic layer, whose Curie temperature is higher than that of the second magnetic layer and lower than that of the first magnetic layer, wherein the first magnetic layer, the fourth magnetic layer, the second magnetic layer and the third magnetic layer are laminated on the substrate in that order, and the perpendicular magnetic anisotropy of each of the first and fourth magnetic layers is smaller than that of the third magnetic layer, said method comprising the steps of:

• rotating the medium;
• projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• moving a domain wall in the first magnetic layer which comes into the region of temperatures when the medium rotates toward a side having a higher temperature in the temperature gradient in the first magnetic layer;
• and
• reproducing the information by detecting reflected rays of the light beam.

An information reproducing method for reproducing information from a magnetooptical recording medium having an information track which comprises a first magnetic layer, a second magnetic layer having a Curie temperature lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, said method comprising the steps of:

• rotating the medium;
• projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• forming a temperature distribution having a gradient in a direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• moving a domain wall in the first magnetic layer, which comes into the region of temperatures when the medium rotates toward a side having a higher temperature in the temperature gradient in the first magnetic layer, wherein the domain wall moves substantially only in a direction along the information track;
• and
• reproducing the information by detecting reflected rays of the light beam.

A magnetooptical recording medium having an information track which comprises:

• a first magnetic layer;
• a second magnetic layer having a Curie temperature lower than that of said first magnetic layer;
• and
• a third magnetic layer for storing information and having a Curie temperature higher than that of said second magnetic layer,
• wherein the perpendicular magnetic anisotropy of said first magnetic layer is smaller than that of said third magnetic layer, and
• wherein a domain wall formed in said first magnetic layer moves substantially only in a direction along the information track.

A recording method for recording information on a magnetooptical recording medium, formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer whose Curie temperature is lower than that of the first magnetic layer, and a third magnetic layer for storing information whose Curie temperature is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and exchange coupling is substantially disconnected between each of the information tracks, said method comprising the steps of:

• rotating the medium;
• projecting a light beam onto the rotating medium;
• and
• recording information by forming a recording magnetic domain not having a domain wall on a portion of its periphery.

An information reproducing apparatus for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer whose Curie temperature is lower than that of the first magnetic layer, and a third magnetic layer for storing information whose Curie temperature is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and the exchange coupling is substantially disconnected between each of the information tracks, said apparatus comprising:

• means for rotating the medium;
• means for projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• means for forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• means for moving a domain wall in the first magnetic layer which comes into the region of temperatures when the medium rotates toward a side having a higher temperature in the temperature gradient in the first magnetic layer;
• means for reproducing the information by detecting reflected rays of the light beam;
• and
• heating means for heating the medium and forming the temperature distribution, said heating means being provided separately from said light beam projecting means.

An information reproducing apparatus for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and between each of the information tracks, a non-magnetic layer or an in-plane magnetic film exists, said apparatus comprising:

• means for rotating the medium;
• means for projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• means for forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• means for moving a domain wall in the first magnetic layer which comes into the region of temperatures when the medium rotates toward a side having higher temperature in the temperature gradient in the first magnetic layer;
• means for reproducing the information by detecting reflected rays of the light beam;
• and
• heating means for heating the medium and forming the temperature distribution, said heating means being provided separately from said light beam projecting means.

An information reproducing apparatus for reproducing information from a magnetooptical recording medium comprising a substrate, a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, a third magnetic layer for storing information, having a Curie temperature that is higher than that of the second magnetic layer, and a fourth magnetic layer, whose Curie temperature is higher than that of the second magnetic layer and lower than that of the first magnetic layer, wherein the first magnetic layer, the fourth magnetic layer, the second magnetic layer and the third magnetic layer are laminated on the substrate in that order, and the perpendicular magnetic anisotropy of each of the first and fourth magnetic layers is smaller than that of the third magnetic layer, said apparatus comprising:

• means for rotating the medium;
• means for projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• means for forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• means for moving a domain wall in the first magnetic layer which comes into the region of temperatures when the medium rotates toward a side having a higher temperature in the temperature gradient in the first magnetic layer;
• means for reproducing the information by detecting reflected rays of the light beam;
• and
• heating means for heating the medium and forming the temperature distribution, said heating means being provided separately from said light beam projecting means.

An information reproducing apparatus for reproducing information from a magnetooptical recording medium having an information track which comprises a first magnetic layer, a second magnetic layer having a Curie temperature lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, said apparatus comprising:

• means for rotating the medium;
• means for projecting a light beam onto the rotating medium from the side of the first magnetic layer;
• means for forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• means for moving a domain wall in the first magnetic layer, which comes into the region of temperatures when the medium rotates toward a side having a higher temperature in the temperature gradient in the first magnetic layer, wherein the domain wall moves substantially only in a direction along the information track;
• means for reproducing the information by detecting reflected rays of the light beam;
• and
• heating means for heating the medium and forming the temperature distribution, said heating means being provided separately from said light beam projecting means.

An information reproducing method for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and exchange coupling is substantially disconnected between each of the information tracks, said method comprising the steps of:

• projecting a light beam onto the medium from the side of the first magnetic layer;
• moving the light beam relative to the medium;
• forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• moving a domain wall in the first magnetic layer which comes into the region of temperatures toward a side having a higher temperature in the temperature gradient in the first magnetic layer;
• and
• reproducing the information by detecting reflected rays of the light beam.

An information reproducing method for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, said method comprising the steps of:

• projecting a light beam onto the medium from the side of the first magnetic layer;
• moving the light beam relative to the medium;
• forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer;
• moving a domain wall in the first magnetic layer which comes into the region of temperatures toward a side having a higher temperature in the temperature gradient in the first magnetic layer, wherein the domain wall moves substantially only in a direction along the information track;
• and
• reproducing the information by detecting reflected rays of the light beam.

A recording method for recording information from a magnetooptical recording medium, formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and exchange coupling is substantially disconnected between each of the information tracks, said method comprising the steps of:

• projecting a light beam onto the medium from the side of the first magnetic layer;
• moving the light beam relative to the medium;
• and
• recording information by forming a recording magnetic domain not having a domain wall on a portion of its periphery.

An information reproducing apparatus for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, and exchange coupling is substantially disconnected between each of the information tracks, said apparatus comprising:

• means for projecting a light beam onto the medium from the side of the first magnetic layer;
• means for moving the first beam relative to the medium;
• heating means for heating the medium and forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer, wherein said heating means being provided separately from said light beam projecting means and the temperature distribution cause a domain wall to move in the first magnetic layer which comes into the region of temperatures toward a side having a higher temperature in the temperature gradient in the first magnetic layer;
• and
• means for reproducing the information by detecting reflected rays of the light beam.

An information reproducing apparatus for reproducing information from a magnetooptical recording medium formed of a film and having a plurality of information tracks, each information track comprising a first magnetic layer, a second magnetic layer having a Curie temperature that is lower than that of the first magnetic layer, and a third magnetic layer for storing information and having a Curie temperature that is higher than that of the second magnetic layer, wherein the perpendicular magnetic anisotropy of the first magnetic layer is smaller than that of the third magnetic layer, said apparatus comprising:

• means for projecting a light beam onto the medium from the side of the first magnetic layer;
• means for moving the light beam relative to the medium;
• heating means for heating the medium and forming a temperature distribution having a gradient in the direction in which the light beam moves relative to the medium and having a region of temperatures higher than the Curie temperature of the second magnetic layer, wherein said heating means being provided separately from said light beam projecting means and the temperature distribution cause a domain wall to move in the first magnetic layer which comes into the region of temperatures toward a side having a higher temperature in the temperature gradient in the first magnetic layer, and the domain wall moves substantially only in a direction along the information track;
• and
• means for reproducing the information by detecting reflected rays of the light beam.