JP2006164436A - Information recording medium, method for manufacturing same and information storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording medium capable of suppressing noise generation in signal reproduction, the information recording medium having a backing layer for enhancing intensity and inclination of a writing magnetic field in a recording layer, and to provide a method for manufacturing the same and an information storage device. <P>SOLUTION: The information recording medium includes: a substrate 2, a recording layer 8, a first backing layer 3 formed of a soft magnetic material; and a second backing layer 4 whose compensation temperature is signal reproduction temperature, and the first backing layer 3, the second backing layer 4 and the recording layer 8 are layered in this order on the substrate 2. By such structure, leakage magnetic fluxes from the respective backing layers 3, 4 to be causes of noise in signal reproduction are suppressed and a recording magnetic field generated from a magnetic head is concentrated in the recording layer 8 by the respective backing layers 3, 4 in the signal reproduction. Thus, the information storage device capable of suppressing the noise resulting from the respective backing layers 3, 4 in the signal reproduction even in the information recording medium having the respective backing layers 3, 4 can be provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an information recording medium for recording and reproducing information by a magnetic action such as a magnetic disk, and more particularly to an information recording medium capable of increasing the recording density of the information recording medium, a manufacturing method thereof, and an information storage device. is there.

  In recent years, with the arrival of an advanced information society, the amount of information handled has become enormous, and there has been a demand for higher capacity and higher density recording devices. In particular, a magnetic recording device with a low bit unit price and capable of non-volatile and large-capacity recording is one of the widely used information storage devices, and development of a magnetic recording medium capable of high-density recording is strongly demanded.

  If the recording density is further improved in the future, in the conventional longitudinal magnetic recording type magnetic recording medium, the recording magnetization becomes unstable due to thermal energy at room temperature, and it becomes difficult to hold the recording bit for a long time. In order to solve this problem, magnetic recording media are shifting to a perpendicular magnetic recording system in which recording magnetization is stabilized as the density is increased.

  In a magnetic recording medium using this perpendicular magnetic recording system, in order to increase the recording density, the recording magnetic field generated by the magnetic head is concentrated in the recording layer with respect to the recording layer that records and holds the magnetization information. What provided the soft-magnetic underlayer which plays a role is known.

  However, the soft underlayer made of a soft magnetic material such as NiFe is divided into magnetic domains having different magnetization directions in the layer, and a large leakage magnetic flux is generated from the domain wall that is the boundary between the magnetic domain and the magnetic domain. To do. The large magnetic flux leakage from the soft magnetic under layer causes large noise called spike noise during signal reproduction.

  As a method for suppressing the occurrence of spike noise from the soft magnetic backing layer, in Patent Document 1, an antiferromagnetic layer made of a manganese-based antiferromagnetic material and a soft magnetic backing layer are provided on a substrate so as to be in contact with each other. The domain wall is controlled by exchange coupling between the two to suppress the formation of the domain wall in the soft magnetic underlayer. Thereby, the leakage magnetic flux from the soft magnetic backing layer is suppressed, and the occurrence of spike noise is reduced.

Further, the magnetic recording medium described in Patent Document 2 is a perpendicular magnetic recording medium including at least perpendicular magnetic recording and a backing layer having magnetization in the in-plane direction backing the perpendicular magnetic recording layer, wherein the backing layer includes: Further, it is made of a ferrimagnetic material having a compensation temperature in the vicinity of the signal reproduction temperature at which the magnetization information recorded in the recording layer is reproduced. As described above, by forming a backing layer, the backing layer has a magnetization when recording magnetization information on the recording layer, and a magnetization when reproducing the magnetization information recorded on the recording layer. It can be in a state not having. Therefore, it is possible to suppress the generation of noise from the backing layer during signal reproduction.
Japanese Patent Laid-Open No. 10-214719 (publication date: August 11, 1998) International publication number: WO 02/095739 (publication date: November 28, 2002)

  However, in the magnetic recording medium described in Patent Document 1, even if the formation of the domain wall in the soft magnetic underlayer is suppressed by the formation of the antiferromagnetic layer, the occurrence of spike noise is sufficiently reduced. Not in.

  Further, in the magnetic recording medium of Patent Document 2, noise from the backing layer at the time of signal reproduction is eliminated, and the problem of spike noise is solved. On the other hand, at the time of signal recording, the backing layer has in-plane magnetization and functions as a backing layer, but since the backing layer is formed of a ferrimagnetic material, the backing layer is formed of a soft magnetic material. In comparison, the magnetic permeability, which is an index of the ease with which the magnetic flux can be taken into the magnetic material, is small, and it is difficult to take the recording magnetic field into the backing layer.

  Therefore, in the magnetic recording medium of Patent Document 2, the effect as the backing layer is smaller than that of the soft magnetic backing layer. In other words, except for the problem of spike noise, it is optimal to use a soft magnetic backing layer as the backing layer in order to better exhibit the effect of the backing layer.

  Here, as described above, the occurrence of spike noise that causes large noise during signal reproduction is caused by a large leakage magnetic flux generated from the domain wall in the soft magnetic underlayer. In general, the strength of the leakage magnetic flux attenuates in inverse proportion to the cube of the distance. For this reason, during signal reproduction, the spacing (interval, distance) between the magnetic head and the soft magnetic backing layer is as large as possible, and the leakage magnetic flux from the backing layer detected by the magnetic head becomes smaller, and the adverse effect of spike noise. Decrease. On the other hand, at the time of signal recording, the effect of the backing layer (concentration of the recording magnetic field) is more remarkable when the spacing between the soft magnetic backing layer and the magnetic head is as small as possible.

  That is, the intensity of the recording magnetic field from the magnetic head for recording is also inversely proportional to the third power of the distance as in the case of the leakage magnetic flux from the backing layer. Therefore, the smaller the spacing between the soft magnetic backing layer and the magnetic head, The recording magnetic field generated by the magnetic head can be more sensitively sensed and induced by the soft magnetic underlayer. Thereby, the recording magnetic field can be further narrowed and the recording magnetic field strength can be increased.

  Therefore, the requirements for the spacing between the magnetic head and the backing layer at the time of signal reproduction and signal recording are contradictory. In response to this requirement, there is a need for a magnetic recording medium having a backing layer that can exhibit good characteristics both during signal recording and during signal reproduction.

  In order to solve this problem, the present invention increases the spacing between the soft magnetic backing layer and the magnetic head during signal reproduction, suppresses leakage magnetic flux from the backing layer that causes noise, and During recording, it is possible to concentrate the recording magnetic field generated from the magnetic head in the recording layer by reducing the spacing between the backing layer and the magnetic head and facilitating the induction of the recording magnetic field to the backing layer. An object of the present invention is to provide an information recording medium having better signal reproduction characteristics than a conventional magnetic recording medium composed of a recording layer and a soft magnetic backing layer.

  In order to solve the above problems, a first information recording medium of the present invention includes at least a substrate, a recording layer, and a backing layer for concentrating a magnetic field used for recording an information signal in the recording layer. The backing layer is composed of a first backing layer formed of a soft magnetic material and a magnetic layer that is formed on the first backing layer and approaches the signal reproduction temperature, and the magnetization decreases in the stacking direction at the signal recording temperature. And a second backing layer having magnetization in a direction perpendicular to the first layer, and a first backing layer, a second backing layer, and a recording layer are laminated in that order on the substrate. It is preferable that the second backing layer has substantially zero magnetization at the signal reproduction temperature.

  According to the above configuration, in the information reproducing apparatus equipped with the first information recording medium of the present invention, at the time of signal reproduction, the second backing layer has substantially reduced magnetization, preferably zero, and leakage magnetic flux to the outside. Decreases (does not leak), so that it can function as a nonmagnetic layer. That is, during signal reproduction, the spacing between the magnetic head and the first backing layer increases due to the presence of the second backing layer with reduced magnetization, and as a result, the first backing layer detected by the magnetic head. The leakage magnetic flux from is reduced. This is because, as described above, the strength of the leakage magnetic flux attenuates in inverse proportion to the cube of the distance. Therefore, in the first information recording medium of the present invention, the influence of noise caused by the leakage magnetic flux from the first backing layer can be reduced during signal reproduction.

  Moreover, according to the above configuration, at the signal recording temperature, the second backing layer has magnetization in the in-plane direction of the substrate that is perpendicular to the stacking direction, and similarly in the in-plane direction of the substrate. It works as a backing layer together with the first backing layer having magnetization. At the time of signal recording, the recording magnetic field generated from the magnetic head is guided to the second backing layer, and then to the first backing layer having a higher magnetic permeability. The recording magnetic field induced into the first backing layer then passes through the first backing layer and again forms a magnetic closed circuit that returns to the magnetic head.

  That is, during signal recording, the strength and gradient of the recording magnetic field can be increased, and the recording resolution of the information recording medium can be improved. In addition, since the second backing layer has magnetization in the in-plane direction of the substrate, the distance between the magnetic head and the first backing layer is magnetically narrowed by the second backing layer, and the recording magnetic field is more sensitive. In comparison with a case where a nonmagnetic layer having a thickness equivalent to that of the second backing layer is provided between the first backing layer and the recording layer by being guided into the first and second backing layers, It is possible to increase the strength and gradient of the recording magnetic field applied to the recording layer.

  In general, the intensity of a recording magnetic field applied to a recording layer by a magnetic head attenuates as it proceeds in the recording layer thickness direction. However, by providing the backing layer as in the information recording medium of the present invention, the recording magnetic field is induced from the surface of the information recording medium to the backing layer, and a magnetic closed circuit is formed between the magnetic head and the backing layer. For this reason, the recording magnetic field can be applied to the recording layer with almost no attenuation of the magnetic field strength in the thickness direction of the recording layer.

  Further, as the strength of the recording magnetic field is increased, the recording magnetic field tends to spread broadly in the in-plane direction of the substrate, and it is difficult to write a small-sized recording bit.

  However, the magnetic closed circuit is formed by providing a backing layer as in the information recording medium of the present invention, and the recording magnetic field is guided downward in the backing layer direction, that is, in the layer thickness direction, and as a result, broadens. The intended recording magnetic field is narrowed down, the application range of the recording magnetic field in the in-plane direction of the substrate can be reduced, and minute recording bits can be written, so that the recording density can be increased.

  In order to solve the above-described problem, the second information recording medium of the present invention has the second backing layer formed of a ferrimagnetic material with respect to the information recording medium having the first configuration of the present invention, and a signal. It has a compensation temperature that is substantially the same as the regeneration temperature.

  According to this, the second backing layer is made of a ferrimagnetic material. The ferrimagnetic material has a compensation temperature at which the amount of magnetization becomes zero. Therefore, the magnetic properties of the ferrimagnetic material forming the second backing layer are adjusted so that the compensation temperature of the second backing layer is substantially the same, for example, according to the signal reproduction temperature of the information recording medium. By doing so, the magnetization of the second backing layer can be reduced, eg, zero or substantially zero, at the signal regeneration temperature. That is, when reproducing the information signal recorded on the recording layer of the information recording medium, the second backing layer has substantially reduced magnetization (becomes zero) and can suppress (do not emit) leakage magnetic flux. Can play a role of non-magnetic layer. Therefore, the first effect of the present invention can be generated more effectively.

  In order to solve the above-described problem, the third information recording medium of the present invention is the first backing layer for the information recording medium having any one of the above-described configurations. And the second backing layer are in contact with each other.

  According to this, since the second backing layer and the first backing layer are in contact with each other, a magnetic exchange coupling force is generated between the two. At the time of signal reproduction, the second backing layer is in a compensation temperature state, and at the time of signal generation (compensation temperature), the second backing layer exhibits an antiferromagnetic magnetization state. Therefore, the domain wall of the first backing layer adjacent to the second backing layer exhibiting an antiferromagnetic magnetization state is fixed in the direction of the magnetic spin related to the second backing layer, and the domain wall due to the stray magnetic field from the outside Movement is suppressed.

  By the way, generally, in the conventional case where an information recording medium having a backing layer formed of a soft magnetic material is mounted on an information reproducing apparatus, a stray magnetic field exists around the magnetic head and the information recording medium during signal reproduction. The stray magnetic field functions to move the domain wall in the backing layer and fluctuate the reproduction output, causing an error in the reproduction signal.

  However, like the third information recording medium of the present invention, the movement of the domain wall of the first backing layer made of soft magnetic material is suppressed by the second backing layer exhibiting an antiferromagnetic magnetization state. Thus, fluctuations in reproduction output can be prevented and errors in the reproduction signal can be suppressed.

  In addition, since the first backing layer and the second backing layer are adjacent to each other, the recording magnetic field guided from the magnetic head to the second backing layer at the time of signal recording is the first with higher permeability. Can be guided more strongly to the backing layer.

  Therefore, the third film configuration of the present invention suppresses the movement of the domain wall in the first backing layer during signal reproduction, and applies a recording magnetic field into the first backing layer with higher permeability during signal recording. An information recording medium that can be guided more strongly can be provided.

  In order to solve the above problems, the fourth information recording medium of the present invention has an average film thickness of the second backing layer of 5 nm or more and 100 nm or less with respect to the information recording medium having any one of the above configurations. It is a feature.

  According to this, the minimum required average film thickness for stably maintaining the magnetic properties of the second backing layer is 5 nm, and when it is equal to or greater than the film thickness, the fourth effect of the present invention is described. The effect of suppressing the movement of the domain wall of the first backing layer by the second backing layer appears. Further, when the information recording medium is heated with laser light to change the magnetic characteristics of the medium as in the optically assisted magnetic recording technique, in order to keep the temperature distribution in the film thickness direction in the medium uniform, The average film thickness of the backing layer needs to be 100 nm or less. Therefore, the average thickness of the second backing layer is 5 nm to 100 nm, more preferably 10 nm to 50 nm.

  In order to solve the above-described problem, the fifth information recording medium of the present invention is an information recording medium having any one of the above-described configurations, wherein the second backing layer includes at least one element selected from rare earth metal elements and And an alloy containing at least one element selected from transition metal elements.

  According to this, the rare earth metal-transition metal alloy is a ferrimagnetic material, and its magnetic characteristics change sharply with respect to temperature. In addition, the compensation temperature and the Curie temperature can be set to desired temperatures by changing the composition ratio between the rare earth metal and the transition metal. Therefore, an information recording medium provided with the second backing layer in accordance with the object of the present invention can be easily manufactured.

  In order to solve the above-mentioned problem, the sixth information recording medium of the present invention is characterized in that the rare earth metal element is at least one of Gd and Ho in the information recording medium having the fifth configuration of the present invention. Further, in order to solve the above problems, the seventh information recording medium of the present invention is different from the information recording medium having the fifth or sixth structure of the present invention in that the transition metal element is Fe, Co, And at least one selected from the group consisting of Ni.

  According to this, the second backing layer made of an alloy obtained by using Gd and / or Ho as the rare earth metal element and Fe, Co, and / or Ni as the transition metal element has a temperature of 150 ° C. or higher. In the high temperature region, the magnetic recording medium can have a large magnetization in a direction perpendicular to the stacking direction of each layer of the information recording medium. Therefore, the above alloy can be suitably used as a ferrimagnetic material forming the second backing layer.

  In order to solve the above problems, an eighth information recording medium of the present invention is provided with a nonmagnetic intermediate layer between the second backing layer and the recording layer with respect to the information recording medium having any one of the above configurations. It is characterized by being.

  According to this, due to the nonmagnetic intermediate layer, a substantially magnetic exchange interaction is not exerted between the second backing layer and the recording layer. Therefore, at the time of signal recording, magnetization can be stably recorded in the direction perpendicular to the substrate without the magnetization direction of the recording layer being dragged to the magnetization direction of the second backing layer.

  In order to solve the above problems, the ninth information recording medium of the present invention is characterized in that the average film thickness of the nonmagnetic intermediate layer is 5 nm or less with respect to the information recording medium having any one of the above configurations. .

  According to this, since the average film thickness of the nonmagnetic intermediate layer is as thin as 5 nm or less, the distance in the film thickness direction between the magnetic head and the second backing layer is added to the eighth effect of the present invention during signal recording. This narrows and makes it easier to guide the recording magnetic field into the second backing layer. Therefore, at the time of signal recording, the strength and gradient of the recording magnetic field applied to the recording layer can be increased, and the recording resolution of the information recording medium can be improved.

  In the present specification, “average film thickness” refers to the film thickness obtained as follows. That is, the same material as that of the film to be measured is formed in a film thickness sufficient to allow the film surface unevenness to be ignored with respect to the film thickness under the same conditions as the film formation conditions of the film to be measured. Then, the film thickness of the formed film is measured. Next, the film thickness (film formation rate) formed per unit time is calculated from the measured film thickness and film formation conditions. And using this film-forming speed | rate, the film thickness of the film | membrane of a measuring object is calculated | required from the film-forming time of a measuring object, and this is made into an "average film thickness."

  In addition, after the production of the information recording medium, the “average film thickness” can be measured by the following method. First, the information recording medium of the present invention is cut in a direction perpendicular to the substrate surface to expose the laminated surface. By exposing the laminated surface, it is possible to observe the laminated state of each layer laminated in order from the substrate side. This cross-sectional view is observed with a transmission electron microscope (TEM) or the like, and the distance in the direction perpendicular to the substrate surface of the layer whose thickness is to be measured is measured at an arbitrary position of 1 μm in the direction of the substrate surface in the information recording medium. The average value is calculated. At this time, the average value of the calculated distances in the direction perpendicular to the substrate surface of the uneven layer is defined as “average film thickness”.

  In order to solve the above problems, a tenth information recording medium of the present invention is a dielectric in which the nonmagnetic intermediate layer is formed of a dielectric material, compared to the information recording medium having the eighth or ninth configuration of the present invention. An uneven layer is formed on the body layer so as to have an uneven shape, and the uneven layer is provided so that the uneven shape is in contact with the recording layer, and the recording layer is at the interface with the uneven layer It is characterized by having an uneven shape.

  According to this, the nonmagnetic intermediate layer includes a dielectric layer and an uneven layer. The uneven layer and the recording layer have an uneven shape at the interface between the uneven layer and the recording layer. Therefore, the concavo-convex layer prevents the movement of the domain wall in the recording layer due to the concavo-convex shape formed at the interface between the concavo-convex layer and the recording layer. That is, the movement of the domain wall formed in the recording layer is restricted within the concave and convex portions formed by the concave and convex shapes. As a result, when the information signal is recorded on the recording layer, the movement of the domain wall can be limited to a short distance as compared with the case where the recording layer does not have an uneven shape. Thereby, a magnetic field can be stably written to the recording layer, and good signal reproduction characteristics can be obtained when reproducing the information recording medium.

  Here, the concavo-convex layer is not necessarily limited to a film shape, but may be distributed in an island shape as individual particles on the layer disposed below the concavo-convex layer, The layer in which these particles are scattered is also collectively referred to as an uneven layer.

  Also, the dielectric layer is not necessarily limited to a film shape, and may be distributed in an island shape as individual particles on the layer disposed below the dielectric layer. The layers in which the particles are scattered are also collectively referred to as a dielectric layer.

  In an eleventh information recording medium of the present invention, in order to solve the above-mentioned problem, the dielectric layer is formed of at least one of a nitride and an oxide, compared to the information recording medium having the tenth configuration of the present invention. In order to solve the above problems, the twelfth information recording medium of the present invention is characterized in that the concavo-convex layer is formed of aluminum with respect to the information recording medium having the tenth or eleventh structure of the present invention. It is characterized by being.

  According to this, a dielectric layer is provided, and an uneven layer of aluminum is formed on the dielectric layer. Therefore, the concavo-convex layer having the concavo-convex shape can be suitably and easily formed. That is, when the dielectric layer is formed of at least one of nitride and oxide, and the uneven layer is formed of aluminum, it is difficult for aluminum to diffuse uniformly over the dielectric layer. Therefore, an uneven layer having an uneven shape can be easily formed by forming an aluminum layer on the dielectric layer. Moreover, since aluminum is used to form the concavo-convex layer, the concavo-convex layer having a fine concavo-convex shape can be formed. Further, when aluminum is used for the uneven layer, it is easy to maintain the uneven shape at the interface between the uneven layer and the recording layer. Therefore, the domain wall movement in the recording layer can be more suitably prevented.

  In order to solve the above problems, the thirteenth information recording medium of the present invention has an average film thickness of the dielectric layer of 2 nm or less compared to the information recording medium having any one of the tenth to twelfth aspects of the present invention. The fourteenth information recording medium of the present invention is characterized in that, in order to solve the above problems, the uneven layer is compared with the information recording medium having any one of the tenth to thirteenth aspects of the present invention. The average film thickness is 3 nm or less.

  According to each configuration described above, the nonmagnetic intermediate layer can be formed with an average film thickness of 5 nm or less. Thus, when recording an information signal, a magnetic field generated from the magnetic head is easily guided to the backing layer through the recording layer and the nonmagnetic intermediate layer. Further, it is possible to prevent the total thickness of the information recording medium from increasing.

  In order to solve the above problems, the fifteenth information recording medium of the present invention has an average surface roughness (Ra) of the concavo-convex layer compared to the information recording medium having any one of the tenth to fourteenth aspects of the present invention. Is 0.6 nm or more and less than 1.5 nm.

  According to this, the average surface roughness of the uneven layer is 0.6 nm or more and 1.5 nm or less. Therefore, the domain wall movement in the recording layer can be effectively suppressed. Thereby, a magnetic field can be stably written to the recording layer, and good signal reproduction characteristics can be obtained when reproducing the information recording medium.

  Note that after the production of the information recording medium, the average surface roughness (Ra) can be measured by the following method. First, as described in the ninth effect of the present invention, the information recording medium of the present invention is cut in a direction perpendicular to the substrate surface to expose the laminated surface. This cross-sectional view is observed with a transmission electron microscope (TEM) or the like, the uneven shape at the interface between the uneven layer and the recording layer is measured, and the average surface roughness (Ra) is calculated.

  Here, the concavo-convex layer is not necessarily limited to a film shape, but may be distributed in an island shape as individual particles on the layer disposed below the concavo-convex layer, The layer in which these particles are scattered is also collectively referred to as an uneven layer.

  In order to solve the above problems, the sixteenth information recording medium of the present invention is the concave / convex layer forming the concavo-convex layer with respect to the information recording medium having any one of the tenth to fifteenth aspects of the present invention. The average diameter of the protrusions in the shape is less than 50 nm at the interface with the recording layer.

  According to this, a minute uneven shape can be formed at the interface between the uneven layer and the recording layer. Thereby, the movement of the domain wall in the recording layer can be effectively suppressed. Thereby, a magnetic field can be stably written to the recording layer, and good signal reproduction characteristics can be obtained when reproducing the information recording medium.

  In order to solve the above problems, the seventeenth information recording medium manufacturing method of the present invention comprises the recording layer, the first backing layer, and the second backing layer, and the first backing layer, the first backing layer, In the method of manufacturing the information recording medium in which the two backing layers and the recording layer are laminated in this order, the second backing layer has a compensation temperature that is substantially the same as the signal reproduction temperature of the information recording medium. The method is characterized by including a step of forming a ferrimagnetic material.

  According to the above method, the backing layer is formed of the ferrimagnetic material so that the compensation temperature of the backing layer is substantially the same as the signal reproduction temperature of the information recording medium. Therefore, when reproducing the information recording medium, the leakage magnetic flux is sufficiently suppressed from the backing layer, and the occurrence of spike noise is reduced. Accordingly, it is possible to provide an information recording medium capable of obtaining good signal reproduction characteristics by reducing noise and improving the quality of the reproduced information signal when reproducing the information signal of the information recording medium. .

  In order to solve the above-described problem, the eighteenth information recording medium manufacturing method of the present invention further includes a dielectric layer and a concavo-convex layer between the second backing layer and the recording layer. Forming a dielectric layer on the backing layer, forming a concavo-convex layer on the dielectric layer so as to have a concavo-convex shape, and forming the recording layer in contact with the concavo-convex shape of the concavo-convex layer. And a step of forming.

  According to said method, the information recording medium which has a dielectric material layer and an uneven | corrugated layer between a backing layer and a recording layer can be manufactured. As a result, it is possible to provide an information recording medium that can stably write a magnetic field on the recording layer and can obtain good signal reproduction characteristics during reproduction of the information recording medium.

  In order to solve the above problems, a nineteenth information storage device of the present invention includes a light irradiation unit that performs light irradiation for locally heating the information recording medium according to any one of the first to sixteenth aspects of the present invention. The information recording medium is heated to a compensation temperature of a magnetic head that magnetically reproduces an information signal with respect to the recording layer of the information recording medium and a second backing layer of the information recording medium. A control unit that controls the light irradiation unit and controls the magnetic head so as to reproduce the information signal recorded on the recording layer in a state where the second backing layer has reached the compensation temperature. It is characterized by that.

  According to this, when reproducing the information signal of the information recording medium, an information storage device such as an information reproducing device capable of reducing noise, improving the quality of the reproduced information signal, and obtaining good signal reproduction characteristics There is an effect that can be provided.

  In order to solve the above problems, a twentieth information storage device according to the present invention includes a light irradiation unit that performs light irradiation for locally heating the information recording medium according to any one of the first to sixteenth aspects of the present invention. The information recording medium is heated to a compensation temperature of a magnetic head for magnetically recording and reproducing information signals with respect to the recording layer of the information recording medium and a second backing layer of the information recording medium. The information signal recorded on the recording layer is reproduced while the light irradiating unit is controlled and the second backing layer reaches the compensation temperature, or the second backing layer is an information recording medium. And a control unit for controlling the magnetic head so as to write an information signal to the recording layer in a state where the temperature has a magnetization in a direction perpendicular to the stacking direction. .

  According to this, at the time of signal reproduction of the information recording medium, spike noise can be reduced and good signal characteristics can be obtained, and at the time of signal recording of the information recording medium, the magnetic field from the magnetic head is efficiently applied to the recording layer. It is possible to provide an information storage device such as an information recording device or an information reproducing device.

  According to a twenty-first information storage device of the present invention, in order to solve the above problems, an information recording medium driving unit that rotationally drives the information recording medium, a head driving unit that drives the light irradiation unit and the magnetic head, And a signal processing unit that converts an information signal recorded on the recording layer of the information recording medium into a reproduction signal that can be reproduced by the information reproduction apparatus.

  As described above, the information recording medium of the present invention has the first backing layer, the second backing layer, and the recording layer laminated in this order on the substrate, and a magnetic field used for recording information signals. The backing layer for concentrating in the recording layer has a first backing layer made of a soft magnetic material and a magnetization formed on the first backing layer as the signal reproducing temperature approaches. And a second backing layer having magnetization in a direction perpendicular to the stacking direction at the signal recording temperature.

  As a result, in the information reproducing apparatus equipped with the information recording medium of the present invention, when the compensation temperature of the second backing layer is set to substantially the same temperature as the signal reproducing temperature, the second backing layer The total amount of magnetization is reduced, for example, becomes zero, so that no leakage magnetic flux is generated, so that it plays a role of a nonmagnetic layer. Thereby, during signal reproduction, the spacing between the magnetic head and the first backing layer is increased, and as a result, the leakage magnetic flux from the first backing layer detected by the magnetic head is reduced. Therefore, in the information recording medium of the present invention, noise due to leakage magnetic flux from the first backing layer is reduced during signal reproduction.

  On the other hand, at the signal recording temperature, the second backing layer has magnetization in the in-plane direction of the substrate, and similarly functions as a backing layer together with the first backing layer having magnetization in the in-plane direction of the substrate. At the time of signal recording, the recording magnetic field generated from the magnetic head is guided to the second backing layer, and then to the first backing layer having a higher magnetic permeability. The recording magnetic field induced into the first backing layer then passes in the in-plane direction of the substrate in the first backing layer, and forms a magnetic closed circuit that returns to the magnetic head again. That is, by forming the magnetic closed circuit when writing magnetization information, the strength and gradient of the recording magnetic field applied to the recording layer can be increased, and the recording resolution of the information recording medium can be improved.

  Therefore, in summary, with the above film configuration, the spacing between the magnetic head and the first backing layer can be increased at the signal reproduction temperature, the spike noise detected by the magnetic head can be suppressed, and the signal At the recording temperature, the second backing layer serves as a backing layer, and together with the first backing layer, induces a recording magnetic field generated from the magnetic head toward the first and second backing layers, It is possible to provide an information recording medium provided with a backing layer capable of increasing the strength and gradient and efficiently applying the recording magnetic field generated from the magnetic head to the recording layer.

  In addition, in the information recording medium of the present invention, a nonmagnetic intermediate layer is provided between the second backing layer and the recording layer, and the nonmagnetic intermediate layer is formed of a dielectric. An uneven layer is formed on the body layer so as to have an uneven shape, and the uneven layer is provided so that the uneven shape is in contact with the recording layer, and the recording layer is at the interface with the uneven layer It is characterized by having an uneven shape.

  As a result, due to the nonmagnetic intermediate layer, almost no magnetic exchange interaction is exerted between the second backing layer and the recording layer. Therefore, during signal recording, the magnetization direction of the second backing layer is not dragged by the magnetization direction of the recording layer, and the magnetization can be stably recorded on the recording layer in the direction perpendicular to the surface of the substrate. .

  In addition, the dielectric layer can significantly form the concavo-convex shape of the concavo-convex layer on the second backing layer. Therefore, a large concavo-convex shape is formed at the interface between the concavo-convex layer and the recording layer, and the formed concavo-convex functions as a domain wall binding site (pinning site) that prevents the movement of the domain wall in the recording layer. For this reason, the magnetic wall movement of the recording layer is suppressed to a short distance compared to a conventional magnetic recording medium composed of a recording layer and a backing layer that does not have an uneven shape at the interface between the recording layer and the layer in contact with the recording layer. Can be formed stably. That is, sufficient signal reproduction characteristics can be obtained even in high-density recording.

  The information recording medium manufacturing method of the present invention includes the recording layer, the first backing layer and the second backing layer as described above, and the first backing layer and the second backing layer on the substrate. In the method of manufacturing the information recording medium in which the recording layer and the recording layer are laminated in order, the second backing layer is ferrimagnetic so as to have a compensation temperature that is substantially the same as the signal reproduction temperature of the information recording medium. It is characterized by including a step of forming with a material.

  According to this method, the backing layer is formed of a ferrimagnetic material so that the compensation temperature of the backing layer is substantially the same as the signal reproduction temperature of the information recording medium. Therefore, when reproducing the information recording medium, the leakage magnetic flux is sufficiently suppressed from the backing layer, and the occurrence of spike noise is reduced. Accordingly, it is possible to provide an information recording medium capable of obtaining good signal reproduction characteristics by reducing noise and improving the quality of the reproduced information signal when reproducing the information signal of the information recording medium. .

  In addition, in the method for manufacturing an information recording medium of the present invention, the information recording medium includes a dielectric layer and an uneven layer between the second backing layer and the recording layer, and the second backing layer. Forming a dielectric layer thereon, forming a concavo-convex layer on the dielectric layer so as to have a concavo-convex shape, and forming the recording layer so as to contact the concavo-convex shape of the concavo-convex layer It is characterized by including.

  According to this method, an information recording medium having a dielectric layer and an uneven layer can be produced between the backing layer and the recording layer. As a result, it is possible to provide an information recording medium that can stably write a magnetic field on the recording layer and can obtain good signal reproduction characteristics during reproduction of the information recording medium.

  The information storage device of the present invention magnetically reproduces an information signal from a light irradiation unit that performs light irradiation for locally heating the information recording medium of the present invention and a recording layer of the information recording medium. And controlling the light irradiation unit to heat the information recording medium to the compensation temperature of the magnetic recording head and the second backing layer of the information recording medium, and the second backing layer is brought to the compensation temperature. And a control unit that controls the magnetic head so as to reproduce the information signal recorded on the recording layer.

  Another information storage device of the present invention includes a light irradiation unit that performs light irradiation for locally heating the information recording medium of the present invention, and a magnetic recording / reproducing of an information signal for the recording layer of the information recording medium. The light irradiation unit is controlled to heat the information recording medium to the compensation temperature of the magnetic head and the second backing layer of the information recording medium, and the second backing layer compensates The information signal recorded on the recording layer is reproduced in a state where the temperature has been reached, or the second backing layer has reached a temperature at which the magnetization is perpendicular to the stacking direction of the information recording medium And a control unit for controlling the magnetic head so as to write an information signal to the recording layer.

  Further, in each of the information storage devices, the information recording medium driving unit that rotates the information recording medium, the head driving unit that drives the light irradiation unit and the magnetic head, and the recording layer of the information recording medium are recorded. It is preferable to include a signal processing unit that converts the information signal into a reproduction signal that can be reproduced by the information reproduction apparatus.

  By using this information storage device, when reproducing the information signal of the information recording medium, noise can be reduced, the quality of the reproduced information signal can be improved, and good signal reproduction characteristics can be obtained. During signal recording on the recording medium, the magnetic field from the magnetic head can be efficiently applied to the recording layer, and the recording density can be increased.

  Hereinafter, embodiments of an information storage device, such as an information recording medium, a manufacturing method thereof, and at least one of an information recording device and an information reproducing device according to the present invention will be described with reference to the accompanying drawings. In each of the embodiments described below, the information recording medium of the present invention is applied to a magnetic disk.

(First embodiment)
In the first embodiment of the information recording medium of the present invention, as shown in FIG. 1, the film structure of the information recording medium 1 is such that the first backing layer 3, the second backing layer 4, A recording layer 8 and a protective layer 9 are laminated in this order, and a lubricating layer 10 is further formed thereon.

  Each layer of the information recording medium 1 according to the first embodiment of the present invention will be described below. First, the substrate 2 is made of a non-magnetic material, and in the present embodiment, glass is used as a material constituting the substrate 2, but it may be made of any of aluminum, plastic, and silicon. . Further, in the present embodiment, the substrate 2 has a flat disk shape, but the substrate 2 may have a cylindrical shape, and in this case, the above layers are laminated on the cylinder outer peripheral surface. To do. The substrate 2 may be of any other material and shape as long as the surface on which the above layers are stacked is smooth and can hold the formed layers without deformation. In addition, it is preferable to clean the surface of the substrate 2 by reverse sputtering or the like before laminating the above layers.

  Next, the first backing layer 3 is made of a soft magnetic material. As a feature of the soft magnetic material used as the backing layer, the soft magnetic material of the core material of the magnetic head, which will be described later, and the magnetic property of the recording layer 8 are used. As compared with the body, those having characteristics such as a high saturation magnetic flux density, a high magnetic permeability, a small coercive force, and a strong magnetic anisotropy in the in-plane direction of the substrate 2 can be mentioned. Since the soft magnetic material has a high magnetic permeability and can easily take in a magnetic field from the outside, it is easy to induce a recording magnetic field generated from the magnetic head to the first backing layer 3 side.

  As a result, the recording magnetic field that was about to spread in the in-plane direction of the substrate 2 is directed downward in the layer thickness direction where the backing layer exists. As a result, the recording magnetic field that is to spread broadly in the in-plane direction of the substrate 2 can be guided downward in the layer thickness direction, and the gradient of the recording magnetic field (in the recording layer 8 at the position facing the magnetic head). The magnetic flux density of the recording magnetic field can be increased.

  Examples of the main first backing layer 3 include crystals such as a permalloy alloy made of an alloy of Ni (nickel) and Fe (iron), a sendust alloy made of an alloy of Al (aluminum), Si (silicon), and Fe (iron). And a non-crystalline backing layer material such as CoZrNb and CoTaZr. The average value of the average thickness of the first backing layer 3 varies depending on the structure and characteristics of the magnetic head used for recording, but is preferably 10 nm or more and 300 nm or less in view of productivity.

  Next, the second backing layer 4 will be described. The second backing layer 4 is made of a ferrimagnetic material whose magnetization amount is substantially zero at both the compensation temperature and the Curie temperature. In other words, the magnetization of the second backing layer 4 decreases as the temperature approaches the compensation temperature (signal regeneration temperature), and when the temperature reaches the compensation temperature, the magnetization becomes substantially zero. Is. The term “substantially zero” refers to a magnetization amount that includes zero and is 10% or less, more preferably 5% or less, and even more preferably 2% or less of the maximum magnetization amount of the magnetic material used for the second backing layer 4. .

  In the present invention, the temperature at which the compensation temperature and the signal reproduction temperature can be regarded as substantially equal (substantially the same temperature) is the second when the information signal recorded on the recording layer 8 of the information recording medium 1 is reproduced. The temperature at which the amount of magnetization of the backing layer 4 becomes substantially zero. The magnetization amount of the second backing layer 4 being substantially zero means that the magnetization amount of the entire second backing layer 4 is such that the noise from the second backing layer 4 is sufficiently suppressed. 2 indicates that the amount of magnetization of the backing layer 4 approaches zero, preferably the amount of magnetization per unit volume is 10 emu / cc or less, preferably zero. Thus, by setting the compensation temperature to substantially the same temperature as the signal reproduction temperature, the magnetization amount of the second backing layer 4 is substantially zero, preferably zero, during signal reproduction of the information recording medium 1. Therefore, the generation of leakage magnetic flux from the second backing layer 4 can be prevented, and the spacing between the magnetic head and the first backing layer 3 is increased.

  In the first embodiment, a HoFeCo alloy thin film that is a rare earth metal-transition metal alloy is used as the second backing layer 4. The HoFeCo alloy thin film can adjust the magnetic characteristics by adjusting the composition ratio of Ho (holmium), which is a rare earth metal, and Fe (iron), which is a transition metal, and Co (cobalt). By adjusting the composition ratio, the second backing layer 4 exhibits a compensation temperature at the signal reproduction temperature, and has magnetization in the in-plane direction (surface direction) of the substrate 2 of the information recording medium 1 at the signal recording temperature. Can be. In the first embodiment, the signal reproduction temperature is set to room temperature (about 30 ° C.) and the signal recording temperature is set to about 240 ° C.

  Here, in the information recording medium 1 of the first embodiment of the present invention, the first backing layer 3 and the second backing layer 4 are provided in contact with each other. According to this, a magnetic exchange coupling force is generated between the second backing layer 4 and the first backing layer 3. At the time of signal reproduction, the second backing layer 4 shows a compensation temperature. At the compensation temperature, the second backing layer 4 has substantially zero magnetization, and thus exhibits an antiferromagnetic magnetization state. Yes. Therefore, the domain wall of the first backing layer 3 adjacent to the second backing layer 4 exhibiting an antiferromagnetic magnetization state is fixed in the direction of the magnetic spin of the second backing layer 4, and the stray magnetic field from the outside The movement of the domain wall due to is suppressed.

  By the way, generally, in the conventional case where an information recording medium having a backing layer formed of a soft magnetic material is mounted on an information recording apparatus or information reproducing apparatus, a stray magnetic field is generated around the magnetic head and the information recording medium during signal reproduction. If present, the stray magnetic field moves through the domain wall in the backing layer, fluctuates the reproduction output, and causes an error in the reproduction signal.

  However, if the movement of the domain wall in the first backing layer 3 made of a soft magnetic material is suppressed by the second backing layer 4 showing an antiferromagnetic magnetization state as in the information recording medium 1. Thus, fluctuations in the reproduction output can be prevented, and errors in the reproduction signal can be suppressed.

  Further, since the first backing layer 3 and the second backing layer 4 are adjacent to each other, the recording magnetic field guided from the magnetic head to the second backing layer 4 during signal recording has a higher magnetic permeability. It can be guided more strongly to the first backing layer 3.

  Therefore, by the film configuration of the first embodiment of the present invention, the movement of the domain wall in the first backing layer 3 is suppressed during signal reproduction, and the magnetic permeability is higher than that of the second backing layer 4 during signal recording. An information recording medium 1 can be provided in which the recording magnetic field can be more strongly guided into the first backing layer 3 and the recording density can be increased.

  The minimum average film thickness required to stably maintain the magnetic properties of the second backing layer 4 is 5 nm. When the thickness is equal to or greater than the above thickness, as described above, the second backing layer 4 Thus, the effect of suppressing the movement of the domain wall of the first backing layer 3 appears. Further, when the information recording medium 1 is heated with laser light to change the magnetic characteristics of the medium as in the optically assisted magnetic recording technology, in order to keep the temperature distribution in the film thickness direction in the information recording medium 1 uniform. The average thickness of the second backing layer 4 is desirably 100 nm or less. Therefore, the average film thickness of the second backing layer 4 is 5 nm to 100 nm, preferably 10 nm to 50 nm.

  Next, the recording layer 8 will be described. In the first embodiment, the recording layer 8 is made of a TbFeCo alloy thin film, which is an amorphous medium and a perpendicular magnetic recording medium having excellent thermal stability. The TbFeCo alloy can adjust the magnetic properties by adjusting the composition ratio of Tb (terbium), which is a rare earth metal, and Fe (iron), which is a transition metal, and Co (cobalt).

The recording layer 8 is made of a rare earth metal-transition metal alloy thin film such as DyFeCo or TbDyFeCo, an alloy thin film composed of at least one transition metal such as Pt and Mn, Fe, Co, or Ni, or Pt / Co. Such as a magnetic multilayer film such as Pd / Co, and a granular magnetic thin film such as CoCr or CoCrPt—SiO ₂ , which has a large perpendicular magnetic anisotropy and is magnetized in a direction perpendicular to the surface of the substrate 2 to stably hold recorded information. If it exists, it is not limited to a TbFeCo alloy thin film.

Here, the recording layer 8 is an alloy thin film composed of Pt and at least one transition metal such as Mn, Fe, Co, Ni, a magnetic multilayer film such as Pt / Co or Pd / Co, CoCr or CoCrPt—SiO 2. _In the case of a crystalline recording layer 8 such as a granular magnetic thin film such as _2, the crystal orientation of the recording layer 8 is improved and lattice defects are suppressed instead of the dielectric layer 5 and the uneven layer 6 described later. Therefore, it is preferable to provide a seed layer (not shown). As a material for the seed layer, a Ti-based alloy such as Ti or TiCr or Ta can be used. However, any material that has an effect of improving the crystal orientation of the recording layer 8 and suppressing lattice defects can be used. The material is not limited.

  FIG. 3 shows the magnetic characteristics of the TbFeCo alloy thin film used in the first embodiment. The vertical axis in FIG. 3 is the remanent magnetization (emu / cc) per unit volume (cc) of the TbFeCo alloy thin film, and the horizontal axis is the temperature (° C.). For the magnetization measurement, the temperature dependence of the residual magnetization was measured using a VSM (Sample Vibration Type Magnetometer) (not shown).

  In the first embodiment, the signal reproduction temperature is set to room temperature (about 30 ° C.) and the signal recording temperature is set to about 240 ° C. In order to match the recording / reproducing operation, as shown in FIG. 3, the recording layer 8 of the information recording medium 1 has a large magnetization at room temperature to increase the reproduction sensitivity, and the coercive force of the recording layer 8 is in the vicinity of 240 ° C. Therefore, the recording magnetic field is set so as to be easily written in the information recording medium 1.

  Next, the protective layer 9 will be described. The protective layer 9 is provided for the purpose of protecting the magnetic layer in order to prevent the magnetic layer of the information recording medium 1 from being scraped when the magnetic head 11 shown in FIG. The protective layer 9 is not particularly limited as long as it can protect the magnetic layer, but in the present embodiment, a carbon-based protective layer 9 such as a carbon layer or a carbon nitride layer is used.

  Next, the lubricating layer 10 will be described. The lubrication layer 10 is for reducing friction at the time of contact with the magnetic head 11 in the information recording apparatus or information reproducing apparatus, and a material conventionally used for a magnetic disk or the like can be used. For example, a fluorine-based lubricant, particularly a perfluoropolyoxyalkane (perfluoropolyether) -based lubricant can be used.

  In the information recording apparatus or information reproducing apparatus equipped with the information recording medium 1 of the first embodiment as described above, when the compensation temperature of the second backing layer 4 is set to the signal reproducing temperature, The second backing layer 4 plays the role of a non-magnetic layer because the total magnetization amount is zero and no leakage magnetic flux is generated.

  That is, at the time of signal reproduction, the spacing between the magnetic head 11 and the first backing layer 3 increases, and as a result, the leakage magnetic flux from the first backing layer 3 detected by the magnetic head 11 decreases. This is because, as described above, the strength of the leakage magnetic flux attenuates in inverse proportion to the cube of the distance. Therefore, in the information recording medium 1 of the first embodiment of the present invention, noise due to leakage magnetic flux from the first backing layer 3 is reduced during signal reproduction.

  On the other hand, at the signal recording temperature, the second backing layer 4 has magnetization in the in-plane direction of the substrate 2, and similarly, the backing layer is combined with the first backing layer 3 having magnetization in the in-plane direction of the substrate 2. Work as. At the time of signal recording, the recording magnetic field generated from the magnetic head 11 is induced to the second backing layer 4 and then to the first backing layer 3 having a higher magnetic permeability.

  The recording magnetic field induced into the first backing layer 3 then passes through the first backing layer 3 and forms a magnetic closed circuit that returns to the magnetic head 11 again. That is, at the time of signal recording, the intensity and gradient of the recording magnetic field can be increased, and the recording resolution of the information recording medium 1 can be improved. In addition, the second backing layer 4 has a magnetization in the in-plane direction of the substrate 2, the distance between the magnetic head 11 and the backing layer is reduced, and the recording magnetic field is guided more sensitively into the backing layer. The strength and gradient of the recording magnetic field applied to the recording layer 8 are further increased as compared with the case where a nonmagnetic layer having the same thickness as the second backing layer 4 is provided between the first backing layer 3 and the recording layer 8. It becomes possible.

  In general, the intensity of the recording magnetic field applied to the recording layer 8 by the magnetic head 11 is attenuated as it advances in the thickness direction of the recording layer 8. However, by providing the backing layer as in the information recording medium 1 of the present invention, the recording magnetic field is induced from the surface of the information recording medium 1 to the backing layer, and a magnetic closed circuit is formed between the magnetic head and the backing layer. . Therefore, the recording magnetic field can be applied to the recording layer 8 with almost no attenuation of the magnetic field strength in the layer thickness direction of the recording layer 8.

  Further, as the intensity of the recording magnetic field is increased, the recording magnetic field tends to spread broadly in the in-plane direction of the substrate 2, and it is difficult to write a small-sized recording bit.

  However, the magnetic closed circuit is formed by providing the first and second backing layers 3 and 4 as in the information recording medium 1 of the present invention, and the recording magnetic field is in the backing layer direction, that is, in the layer thickness direction. As a result, the recording magnetic field to be broadened is narrowed down. As a result, the application range of the recording magnetic field in the in-plane direction of the substrate 2 can be reduced, and minute recording bits can be written.

  Therefore, in summary, according to the first film configuration of the present invention, the spacing between the magnetic head 11 and the first backing layer 3 can be increased at the signal reproduction temperature, and spike noise detected by the magnetic head 11 can be reduced. The reproduced signal quality can be improved by suppressing the second backing layer 4 as a backing layer at the signal recording temperature, and the recording magnetic field generated from the magnetic head 11 together with the first backing layer 3 is used as the backing layer. An information recording medium 1 having a backing layer capable of improving the recording density by increasing the strength and gradient of the recording magnetic field and efficiently applying the recording magnetic field generated from the magnetic head 11 to the recording layer 8. Can be provided.

Next, a method for manufacturing the information recording medium 1 will be described. First, a glass substrate for a magnetic disk having a diameter of 2.5 inches is set as a substrate 2 in a sputter film forming apparatus (not shown), and a chamber (not shown) of the film forming apparatus in which the substrate 2 is set is set in 3. It exhausted until it became the vacuum degree of * 10 <^-5> Pa.

  Next, a NiFe film was formed as the first backing layer 3 on the substrate 2 by a magnetron sputtering method and co-sputtering with a Ni and Fe binary target so as to have an average film thickness of 25 nm. . As sputtering conditions, sputtering gas pressure was 0.2 Pa, sputtering input power was DC voltage (DC), Ni was 429 W, Fe was 112 W, and argon (Ar) gas was used as sputtering gas. As a result of measuring the composition ratio with a fluorescent X-ray analyzer (XRF), the composition ratio of each element was measured to be 80.2 at%: 19.8 at% for Ni: Fe.

  Next, a HoFeCo alloy thin film was formed as a second backing layer 4 on the first backing layer 3 by co-sputtering using a ternary target of Ho, Fe, and Co, using a magnetron sputtering method. As sputtering conditions, sputtering gas pressure was 0.2 Pa, sputtering input power was DC voltage (DC), Ho was 383 W, Fe was 200 W, Co was 632 W, and argon (Ar) gas was used as sputtering gas. As a result of measuring the composition ratio with a fluorescent X-ray analyzer (XRF), the composition ratio of each element was determined to be 23.3 at%: 17.3 at%: 59.4 at% for Ho: Fe: Co.

  After the second backing layer 4 was formed, a TbFeCo alloy thin film was formed as the recording layer 8, and three targets of Tb, Fe, and Co were formed by co-sputtering by magnetron sputtering. As sputtering conditions, sputtering gas pressure was 0.2 Pa, sputtering input power was DC voltage (DC), Tb was 72 W, Fe was 200 W, Co was 39 W, and argon (Ar) gas was used as sputtering gas. As a result of measuring the composition ratio with a fluorescent X-ray analyzer (XRF), the composition ratio of each element was measured as follows: Tb: Fe: Co: 17.0 at%: 68.9 at%: 14.1 at%.

  After the recording layer 8 was formed, an amorphous carbon (a-C) film was formed as the protective layer 9 by DC magnetron sputtering so that the average film thickness was 10 nm. The sputtering conditions were a sputtering gas pressure of 1.0 Pa, a sputtering power of DC 300 W, and argon (Ar) gas as the sputtering gas.

  After the formation of the protective layer 9, a perfluoropolyoxyalkane-based lubricant was applied to the interface of the amorphous carbon film by a dip coater as the lubricating layer 10 to form a liquid lubricating film having a thickness of 0.8 nm. Note that, after forming the protective film 9, tape burnishing may be performed, and then the lubricating layer 10 may be formed.

  The magnetic characteristics of the first backing layer 3, the second backing layer 4 and the respective layers at the signal reproduction temperature (about 30 ° C.) of the information recording medium 1 of the present invention manufactured as described above are shown in FIGS. As shown in FIG. The magnetic properties of the first backing layer 3, the second backing layer 4, and the respective layers at the signal recording temperature (about 240 ° C.) are shown in FIGS.

  In the sample used for the magnetic property measurement, each of the above layers was formed on the substrate 2 under the same conditions as those for the production of the information recording medium 1, and an Al film was formed thereon with a thickness of 50 nm to prevent oxidation. Laminated and produced.

  Magnetization measurement of the manufactured sample was performed by cutting into a 1 cm × 1 cm diameter in the in-plane direction of the substrate 2 and using a VSM (sample vibration type magnetometer) (not shown). 4 to FIG. 7, the vertical axis represents the amount of magnetization (emu / cc) per unit volume detected by the VSM, the horizontal axis represents the applied magnetic field (Oe) applied from the outside, and the in-plane direction of the substrate 2. The amount of magnetization of was measured.

  From the measurement results, as shown in FIGS. 4 and 5, at the signal regeneration temperature (about 30 ° C.), the second backing layer 4 shows the compensation temperature, and the magnetization amount is zero. It can be seen that one backing layer 3 exhibits a large in-plane magnetization of the substrate 2.

  Therefore, in the information recording apparatus or information reproducing apparatus equipped with the information recording medium 1 of the first embodiment, the second backing layer 4 has a total magnetization amount of zero and does not emit leakage magnetic flux during signal reproduction. It plays the role of a nonmagnetic layer. That is, at the time of signal reproduction, the spacing between the magnetic head 11 and the first backing layer 3 increases, and as a result, the leakage magnetic flux from the first backing layer 3 detected by the magnetic head 11 decreases. This is because the strength of the leakage magnetic flux attenuates in inverse proportion to the cube of the distance. Therefore, in the information recording medium 1 of the first embodiment of the present invention, noise due to leakage magnetic flux from the first backing layer 3 is reduced during signal reproduction.

  Further, since the second backing layer 4 and the first backing layer 3 are adjacent to each other, a magnetic exchange coupling force is generated between them. At the time of signal reproduction, the second backing layer 4 shows a compensation temperature, and at the compensation temperature, the second backing layer 4 shows an antiferromagnetic magnetization state. Therefore, the domain wall of the first backing layer 3 adjacent to the second backing layer 4 exhibiting an antiferromagnetic magnetization state is fixed in the direction of the magnetic spin of the second backing layer 4, and the stray magnetic field from the outside The movement of the domain wall due to is suppressed.

  By the way, generally, in the conventional case where an information recording medium having a backing layer formed of a soft magnetic material is mounted on an information recording apparatus or information reproducing apparatus, a stray magnetic field is generated around the magnetic head and the information recording medium during signal reproduction. If present, the stray magnetic field moves through the domain wall in the backing layer, fluctuates the reproduction output, and causes an error in the reproduction signal.

  However, as in the information recording medium 1 according to the first embodiment, if the movement of the domain wall in the first backing layer 3 is suppressed by the second backing layer 4 showing the antiferromagnetic magnetization state, Variations in the reproduction output can be prevented, and errors in the reproduction signal can be suppressed.

  Here, in order to make the effect of suppressing the movement of the domain wall in the first backing layer 3 by the second backing layer 4, the average thickness of the second backing layer 4 is 5 nm or more. desirable. Further, when the information recording medium 1 is heated with laser light to change the magnetic characteristics of the information recording medium 1 as in the optically assisted magnetic recording technology, the temperature distribution in the film thickness direction in the information recording medium 1 is kept uniform. For this purpose, the average film thickness of the second backing layer 4 is desirably 100 nm or less. Therefore, the average film thickness of the second backing layer 4 is not less than 5 nm and not more than 100 nm, more preferably not less than 10 nm and not more than 50 nm.

  From the measurement results, as shown in FIGS. 6 and 7, both the second backing layer 4 and the first backing layer 3 are large in the in-plane direction of the substrate 2 at the signal recording temperature (about 240 ° C.). It can be seen that it shows magnetization.

  Here, the magnetic permeability μ is expressed by μ = B / H when the magnetic permeability, which is an index indicating the ease of taking in the magnetic flux into the magnetic body, is described. B represents a magnetic flux density, H represents an applied magnetic field, and the magnetic flux density B is substantially proportional to the magnetization M. Therefore, in the same applied magnetic field, the greater the magnetization per unit volume, the greater the permeability. In other words, in the same applied magnetic field, the larger the magnetization per unit volume, the easier the magnetic flux is taken into the layer, and the recording magnetic field can be narrowed down.

  Considering the above matters and looking at the magnetization saturation region in the magnetization history curves of FIGS. 6 and 7, the first backing layer 3 has a larger magnetic permeability than the second backing layer 4 during signal recording. It can be seen that the magnetic flux can be easily taken in and the recording magnetic field can be narrowed down more strongly.

  Therefore, in the information recording apparatus or information reproducing apparatus equipped with the information recording medium 1 of the first embodiment of the present invention, the second backing layer 4 has magnetization in the in-plane direction of the substrate 2 at the signal recording temperature. The first backing layer 3 having magnetization in the in-plane direction of the substrate 2 functions as a backing layer. At the time of signal recording, the recording magnetic field generated from the magnetic head 11 is induced to the second backing layer 4 and then to the first backing layer 3 having a higher magnetic permeability.

  The recording magnetic field induced into the first backing layer 3 then passes through the first backing layer 3 and forms a magnetic closed circuit that returns to the magnetic head 11 again. That is, at the time of signal recording, the intensity and gradient of the recording magnetic field can be increased, and the recording resolution of the information recording medium 1 can be improved. In addition, the second backing layer 4 has a magnetization in the in-plane direction of the substrate 2, the distance between the magnetic head 11 and the backing layer is reduced, and the recording magnetic field is guided more sensitively into the backing layer. The strength and gradient of the recording magnetic field applied to the recording layer 8 are further increased as compared with the case where a nonmagnetic layer having the same thickness as the second backing layer 4 is provided between the first backing layer 3 and the recording layer 8. It becomes possible.

  In general, the intensity of the recording magnetic field applied to the recording layer 8 by the magnetic head 11 is attenuated as it advances in the thickness direction of the recording layer 8. However, by providing a backing layer as in the information recording medium 1 of the present invention, the recording magnetic field is induced from the surface of the information recording medium 1 to the backing layer, and a magnetic closed circuit is formed between the magnetic head 11 and the backing layer. To do. Therefore, the recording magnetic field can be applied to the recording layer 8 with almost no attenuation of the magnetic field strength of the recording layer 8 in the layer thickness direction.

  Further, as the intensity of the recording magnetic field is increased, the recording magnetic field tends to spread broadly in the in-plane direction of the substrate 2, and it is difficult to write a small-sized recording bit. However, the magnetic closed circuit is formed by providing the backing layer as in the information recording medium 1 of the present invention, and the recording magnetic field is guided downward in the backing layer direction, that is, in the layer thickness direction. It is possible to narrow the recording magnetic field to be removed, reduce the application range of the recording magnetic field in the in-plane direction of the substrate 2, and write a minute recording bit.

  In the first embodiment, the signal reproduction temperature is room temperature (about 30 ° C.) and the signal recording temperature is about 240 ° C., but both are not limited to the above temperature. However, when the temperature is changed, it is necessary to change the magnetic properties of the recording layer 8 and the second backing layer 4. For example, when the signal reproduction temperature is set near 90 ° C., the second backing layer 4 has a compensation temperature near 90 ° C., and near the signal recording temperature, it is large in the in-plane direction of the substrate 2 of the information recording medium 1. It is necessary to adjust the magnetic characteristics so that the magnetization comes. That is, the second backing layer 4 has a compensation temperature that does not generate a leakage magnetic field at the time of signal reproduction, and the magnetic characteristics are set so that a large magnetization comes in the in-plane direction of the substrate 2 of the information recording medium 1 at the time of signal recording. Need to be. The recording layer 8 needs to have a magnetic characteristic that generates a large leakage magnetic field during signal reproduction and has a smaller coercive force than the write magnetic field from the magnetic head 11 during signal recording.

  Further, in the first embodiment, the magnetic properties of the second backing layer 4 are uniformly produced in the information recording medium 1. The lining magnetic layer may be formed by changing the magnetic characteristics in the direction and by multilayering the ferrimagnetic material.

  In the first embodiment, the magnetic properties of the second backing layer 4 are made uniform with respect to the disk radial direction of the information recording medium 1. It may be changed between the peripheral side and the outer peripheral side.

(Second embodiment)
As shown in FIG. 2, the film configuration of the information recording medium according to the second embodiment of the present invention is such that the first backing layer 3, the second backing layer 4, the dielectric layer 5, and the unevenness are formed on the substrate 2. The nonmagnetic intermediate layer 7 including the layer 6, the recording layer 8, and the protective layer 9 are laminated in this order, and a lubricating layer 10 is further formed thereon, and is formed into a disk shape.

  Here, in the information recording medium 19 configured as described above, the layers other than the nonmagnetic intermediate layer 7 are in accordance with the description of the first embodiment, and the description after the formation of the information recording medium 19 is also the same as in the first embodiment. Follow the instructions. The nonmagnetic intermediate layer 7 will be described below.

  The nonmagnetic intermediate layer 7 is disposed between the second backing layer 4 and the recording layer 8 and includes a dielectric layer 5 and an uneven layer 6. By providing the nonmagnetic intermediate layer 7, magnetic exchange interaction is prevented from occurring between the second backing layer 4 and the recording layer 8. Therefore, when recording a signal on the information recording medium 19, the magnetization direction of the recording layer 8 is prevented from being influenced by the magnetization direction of the second backing layer 4, and signal recording with good signal quality is realized. can do.

  The nonmagnetic intermediate layer 7 has a concavo-convex shape on the surface of the nonmagnetic intermediate layer 7 facing the recording layer 8 in order to induce a pinning effect that prevents (stops) the movement of the domain wall on the recording layer 8. It is provided as follows. That is, the nonmagnetic intermediate layer 7 has a minute uneven shape at the interface with the recording layer 8 formed on the nonmagnetic intermediate layer 7. This uneven shape serves as a domain wall binding site (pinning site) that prevents the domain wall in the recording layer 8 from moving. In other words, the magnetic domain formed in the recording layer 8 is divided by the uneven shape of the nonmagnetic intermediate layer 7, and is limited within each concave portion or each convex portion forming the concave and convex shape. For this reason, the moving distance of the domain wall, which is the boundary between the magnetic domains, is limited depending on the size of the concave portion or the convex portion having the concave and convex shape.

  Therefore, by the pinning effect due to the uneven shape of the nonmagnetic intermediate layer 7, the moving distance of the domain wall in the recording layer 8 can be limited within the concave portion and the convex portion, and minute recording bits can be stably formed in the recording layer 8. . Thereby, high-density recording can be realized on the information recording medium 19. Further, when reproducing the signal recorded on the recording layer 8, since the movement of the domain wall of the recording layer 8 is limited, good signal reproduction characteristics can be obtained when reproducing the signal of the information recording medium 19.

  Here, the upper limit of the average film thickness of the nonmagnetic intermediate layer 7 is 5 nm or less, preferably 4 nm or less, and more preferably 3 nm or less. The lower limit of the average film thickness is not particularly limited, but is preferably 1 nm or more, and more preferably 1.2 nm or more.

  When the average film thickness exceeds 5 nm, the distance between the magnetic head of the recording / reproducing apparatus (to be described later) and the second backing layer 4 is increased during signal recording on the recording layer 8 of the information recording medium 19, and the distance from the magnetic head is increased. There is a tendency that it is difficult to induce a recording magnetic field for writing to the second backing layer 4. As a result, the strength and gradient of the recording magnetic field applied to the recording layer 8 tend to decrease, which makes it difficult to improve the recording resolution. Another problem is that the thickness of the nonmagnetic intermediate layer 7 tends to increase, and the entire thickness of the information recording medium 19 tends to increase.

  On the other hand, if the average film thickness is less than 1 nm, it tends to be difficult to prevent the occurrence of magnetic exchange interaction between the second backing layer 4 and the recording layer 8, which is not preferable. .

  The average film thickness is a value calculated by any of the following methods. That is, with the same material as the material constituting the measurement target layer, the surface roughness of the layer can be ignored with respect to the layer thickness (film thickness) under the same conditions as the film formation conditions of the measurement target layer. A film having a sufficient thickness is formed, and the film thickness of the formed layer is measured. Next, the film thickness (film formation speed) formed per unit time is calculated from the measured film thickness and film formation conditions. And using this film-forming speed | rate, the film thickness of the film | membrane of a measuring object is calculated | required from the film-forming time of a measuring object, and this is made into an average film thickness.

  Further, after the production of the information recording medium 19, the average film thickness is measured by the following method. That is, first, the information recording medium 19 is cut in a direction perpendicular to the surface of the substrate 2, and the laminated surface of each layer, which is the cut surface, is observed with a transmission electron microscope (TEM) or the like. Then, in the information recording medium 19, a range of 1 μm is set in the in-plane direction, and a layer whose thickness is to be measured at a plurality of different locations within the 1 μm range is perpendicular to the surface of the substrate 2. Measure the distance in the direction. Subsequently, an average value is calculated for the distances in the vertical direction measured at a plurality of locations within the range of 1 μm, and this average value is taken as an average film thickness.

  Of the nonmagnetic intermediate layer 7, the dielectric layer 5 is provided in contact with the second backing layer 4, and the uneven layer 6 for inducing the uneven shape of the nonmagnetic intermediate layer 7 can be easily formed. Provided to form. The dielectric layer 5 may be a layer made of a dielectric, and at least one of nitride and oxide may be used.

  In general, a metal film formed on a nitride or an oxide is difficult to diffuse, and thus is not formed uniformly but is formed to have an uneven shape. By utilizing this property, the nonmagnetic intermediate layer 7 having an uneven shape can be easily formed. Therefore, in this embodiment, the dielectric layer 5 is formed of at least one of nitride and oxide. A concavo-convex layer 6 of a metal film is formed on the dielectric layer 5. Therefore, the uneven layer 6 of the nonmagnetic intermediate layer 7 is disposed so as to be in contact with the recording layer 8.

  Here, the nitride forming the dielectric layer 5 is not particularly limited, and examples thereof include one or more selected from silicon nitride (SiN), aluminum nitride, titanium nitride, and the like. . In addition, the oxide forming the dielectric layer 5 is not particularly limited, and examples thereof include one or more selected from silicon oxide, aluminum oxide, titanium oxide, silver oxide, platinum oxide, and the like. Can do.

  The dielectric layer 5 has an upper limit value of the average film thickness measured by the above-described method of 2 nm or less, preferably 1.5 nm or less, and more preferably 1 nm or less.

  The lower limit of the average film thickness is not particularly limited, but is preferably 0.4 nm or more, and more preferably 0.6 nm or more. If the average film thickness exceeds 2 nm, the thickness of the information recording medium 19 increases, which is not preferable. On the other hand, when the average film thickness is less than 0.4 nm, it becomes difficult to uniformly form the dielectric layer 5 on the second backing layer 4. Therefore, when the concavo-convex layer 6 is formed on the heterogeneous dielectric layer 5, the concavo-convex structure at the interface between the concavo-convex layer 6 and the recording layer 8 varies, and the characteristics of the recording layer 8 are controlled. It is not preferable.

  When the surface of the second backing layer 4 is nitrided or oxidized by plasma etching or the like, the surface of the second backing layer 4 that has been nitrided or oxidized may be used as the dielectric layer 5.

  Moreover, the said uneven | corrugated layer 6 should just be a layer which consists of nonmagnetic metals, for example, aluminum, zinc, etc. may be used. Among these, aluminum has a large average surface roughness Ra described later. Further, the aluminum is easily chemically bonded by forming a compound with a metal film forming the recording layer 8 to be described later, and easily maintains the uneven shape. Therefore, a high pinning effect can be expected. Therefore, the concavo-convex layer 6 is preferably formed using aluminum.

  Moreover, as for the said uneven | corrugated layer 6, the upper limit of the average film thickness measured by an above-described method is 3 nm or less, it is preferable that it is 2.5 nm or less, and it is more preferable that it is 2 nm or less. The lower limit of the average film thickness is not particularly limited, but is preferably 1 nm or more, and more preferably 1.5 nm or more. If the average film thickness exceeds 3 nm, the thickness of the information recording medium 19 increases, which is not preferable. On the other hand, when the average film thickness is less than 1 nm, the average surface roughness Ra of the concavo-convex structure at the interface between the concavo-convex layer 6 and the recording layer 8 decreases, and the domain wall binding site (which prevents movement of the domain wall in the recording layer 8) The effect as a pinning site is difficult to occur, which is not preferable.

  Furthermore, the average surface roughness Ra of the uneven layer 6 is preferably larger than the average surface roughness Ra of the second backing layer 4. Specifically, the upper limit value of the average surface roughness Ra of the uneven layer 6 is 1.5 nm or less, preferably 1.3 nm or less, and more preferably 1.1 nm or less.

  Further, the lower limit value of the average surface roughness Ra is not particularly limited as long as it is larger than the average surface roughness Ra of the second backing layer 4, but is preferably 0.6 nm or more, preferably 0.8 nm or more. More preferably. When the average surface roughness Ra exceeds 1.5 nm, the diameter of the convex portions formed on the concave / convex layer 6 becomes large, and it becomes difficult to form a fine concave / convex shape in the recording layer 8.

  As a result, since it becomes difficult to form minute recording bits in the information recording medium 19, in order to perform high-density recording with sufficient signal quality, the average surface roughness Ra is set to 1.5 nm or less. It is preferable. On the other hand, when the average surface roughness Ra is less than 0.6 nm, since the average surface roughness Ra of the concavo-convex structure at the interface between the concavo-convex layer 6 and the recording layer 8 is small, the domain wall in the recording layer 8 is moved. Since the effect as a domain wall binding site (pinning site) to be hindered is difficult to occur, it is not preferable.

  Here, the average surface roughness Ra is based on the definition of JIS B 0601-1982, and represents the centerline average roughness related to the amplitude of fine irregularities. Note that after the information recording medium 19 is manufactured, the average surface roughness Ra may be measured by the following method. That is, the information recording medium 19 is cut in a direction perpendicular to the surface of the substrate 2, and the laminated surface of each layer, which is the cut surface, is observed with the TEM or the like. Then, the uneven shape at the interface between the uneven layer 6 and the recording layer 8 may be measured to calculate the average surface roughness.

  The upper limit of the diameter of the convex portion formed on the concave-convex layer 6 on the surface of the concave-convex layer 6, that is, the interface between the concave-convex layer 6 and the recording layer 8, is preferably less than 50 nm and 45 nm or less. More preferably, it is 40 nm or less. The lower limit value of the convex portion is not particularly limited, but is preferably 15 nm or more, and more preferably 20 nm or more. If the diameter of the convex portion is 50 nm or more, it is difficult to form a minute uneven shape in the recording layer 8 and it is difficult to suppress the moving distance of the domain wall in the recording layer 8. Is not preferable.

  Here, the convex portion refers to a portion that is higher along the stacking direction of each layer of the information recording medium 19 with respect to the bottom portion of the concave portion. Further, the diameter of the convex portion means an average value of the sizes of the convex portions formed on the uneven layer 6.

  The dielectric layer 5 may be formed as a film on the second backing layer 4 to form a layer as described above, or a dielectric layer 5 may be formed on the second backing layer 4. The compound which forms the body layer 5 may be arranged so as to be scattered as particles and form a layer. That is, the dielectric layer 5 may be a layer in which compounds such as nitrides and oxides described above are dispersed on the second backing layer 4 and distributed in an island shape.

  The uneven layer 6 may be formed in a film shape and have an uneven shape, or may be arranged so as to be scattered on the dielectric layer 5 to have an uneven shape. That is, the concavo-convex layer 6 may be a layer in which the nonmagnetic metal used for the concavo-convex layer 6 becomes particles and is scattered on the dielectric layer 5 and arranged in an island shape. .

  When at least one of the dielectric layer 5 and the uneven layer 6 is formed in an island shape, the lower limit value of the average surface roughness Ra depends on the average surface roughness of each layer disposed below the uneven layer 6. It will be.

  Therefore, it is difficult to specify the lower limit value of the average surface roughness Ra of the uneven layer 6. Usually, the average surface roughness of the substrate 2 is about 0.48 nm, the average surface roughness of the second backing layer 4 using the HoFeCo alloy is about 0.38 nm, and aluminum is used as the uneven layer 6. Since the atomic radius of aluminum is 1.43 mm (0.143 nm), the lower limit value of the average surface roughness Ra of the uneven layer 6 is considered to be about 0.6 nm.

  Next, the surface shape of the uneven layer 6 will be described below. On the substrate 2, a NiFe film (thickness 25 nm) is used as the first backing layer 3, a HoFeCo film (thickness 25 nm) is used as the second backing layer 4, and an aluminum nitride (AlN) film (thickness 2 nm is used as the dielectric layer 5). ), An aluminum (Al) film (film thickness: 3 nm) is laminated in this order as the concavo-convex layer 6, the surface shape of the concavo-convex layer 6 is observed with an atomic force microscope (AFM), and the average surface roughness (Ra) at that time is measured. did. The method for preparing the AFM observation sample is as follows.

First, a glass substrate is used as the substrate 2, and this is installed in a sputter film forming apparatus (not shown), and the inside of the chamber (not shown) of the sputter film forming apparatus is a vacuum degree of less than 3 × 10 ⁻⁵ Pa. Exhausted.

  Next, a NiFe film was formed as the first backing layer 3 on the substrate 2 by a magnetron sputtering method and co-sputtering with a Ni and Fe binary target so as to have an average film thickness of 25 nm. . As sputtering conditions, sputtering gas pressure was 0.2 Pa, sputtering input power was DC voltage (DC), Ni was 429 W, Fe was 112 W, and argon (Ar) gas was used as sputtering gas. As a result of measuring the composition ratio with a fluorescent X-ray analyzer (XRF), the composition ratio of each element was measured to be 80.2 at%: 19.8 at% for Ni: Fe.

  Next, as the second backing layer 4, a HoFeCo film was formed to have an average film thickness of 25 nm by co-sputtering using a ternary target of Ho, Fe, and Co using a magnetron sputtering method. As sputtering conditions, sputtering gas pressure was 0.2 Pa, sputtering input power was DC voltage (DC), Ho was 383 W, Fe was 200 W, Co was 632 W, and argon (Ar) gas was used as sputtering gas. As a result of measuring the composition ratio with a fluorescent X-ray analyzer (XRF), the composition ratio of each element was determined to be 23.3 at%: 17.3 at%: 59.4 at% for Ho: Fe: Co.

After the second backing layer 4 was formed, an AlN film was formed as the dielectric layer 5 by a reactive sputtering method so as to have an average film thickness of 2 nm. The sputtering conditions were a sputtering gas pressure of 0.08 Pa, a sputtering input power of 2 kW at a high frequency voltage (RF), and argon (Ar) and nitrogen gas (N ₂ ) as sputtering gases.

  After the dielectric layer 5 was formed, an aluminum film was formed as the uneven layer 6 so as to have an average film thickness of 3 nm by using a magnetron sputtering method. After the formation of the concavo-convex layer 6, a sample (hereinafter referred to as “sample A”) is taken out from the chamber, and the surface shape of the concavo-convex layer 6 (aluminum film) is measured by an atomic force microscope (AFM) as shown in FIG. Observed. The observation image is shown. FIG. 8 shows that the surface of the concavo-convex layer 6, which is an aluminum film, has an average surface roughness (Ra) of 1.0 nm and has a concavo-convex shape with a very large surface roughness.

  As a comparative sample, a sample in which a NiFe film and a HoFeCo film were sequentially formed on the substrate 2 so as to have an average film thickness of 25 nm (hereinafter referred to as sample B) using the same film formation conditions as in the above sample A. Was prepared as a first comparison layer 26 as shown in FIG. Further, a sample (hereinafter referred to as sample C) in which a NiFe film and a HoFeCo film are respectively formed on the substrate 2 in the order of 25 nm and an aluminum film in the order of 5 nm using the same film formation conditions as the sample A is shown in FIG. A second comparative layer 36 was prepared. The samples B and C were also observed with an atomic force microscope (AFM). Moreover, the average surface roughness (Ra) of each sample surface was measured by observation of FIG. 8, FIG. 9, FIG. The average surface roughness (Ra) of each sample A, sample B, and sample C was measured as 1.0 nm, 0.38 nm, and 0.43 nm, respectively.

  From FIG. 9, it can be seen that the average surface roughness (Ra) of the first comparison layer 26 which is the surface of the second backing layer 4 (HoFeCo film) is very small and has a flat surface shape.

  From FIG. 10, the average surface roughness (Ra) is also flat (surface roughness) for the second comparison layer 36, which is a surface on which an Al film (5 nm) is formed on the second backing layer 4 (HoFeCo film). Is small). Therefore, the second backing layer is formed by sequentially laminating the aluminum nitride (AlN) film as the dielectric layer 5 and the aluminum (Al) film as the uneven layer 6 on the second backing layer 4 (HoFeCo film). It can be seen that the uneven layer 6 having a surface roughness larger than 4 (HoFeCo film) can be easily formed.

  Next, a method for manufacturing the information recording medium 19 according to the second embodiment will be described. The above manufacturing method is the information described in the first embodiment except that the nonmagnetic intermediate layer 7 including the dielectric layer 5 and the uneven layer 6 is provided between the second backing layer 4 and the recording layer 8. The manufacturing method of the recording medium 1 is followed. The film forming conditions for the dielectric layer 5 and the concavo-convex layer 6 after the second backing layer 4 is formed are shown below.

After the second backing layer 4 was formed, an AlN film was formed to a dielectric layer 5 by using a reactive sputtering method so that the average film thickness was 2 nm. The sputtering conditions at this time were a gas pressure of 0.08 Pa, an input power of 2 kW with a high frequency voltage (RF), and Ar gas and N ₂ (nitrogen) gas as sputtering gases. Next, an Al film was formed on the dielectric layer 5 so as to have an average film thickness of 3 nm by using a magnetron sputtering method, thereby forming an uneven layer 6. Thereafter, similarly to the first embodiment, a recording layer 8 and a protective layer 9 were laminated in this order, and a lubricating layer 10 was further formed thereon.

(Third embodiment)
Hereinafter, an embodiment of the information storage device 16 as an information recording device or an information reproducing device using the information recording medium 1 manufactured in the first embodiment will be described as a third embodiment of the present invention. .

  As shown in FIGS. 11 and 12, the information storage device 16 of the present embodiment includes the information recording medium 1 manufactured in the present embodiment and an information recording medium driving unit for rotating the information recording medium 1. 13, a light irradiation unit 12 for irradiating a laser beam for locally heating the information recording medium 1, and a magnetic head 11 for recording information in the information recording medium 1 and reproducing the recorded information A recording / reproducing system driving unit 14 for driving the magnetic head 11 and the light irradiation unit 12, and a recording / reproducing signal processing system 15.

  The principle of recording and reproducing information using the information storage device 16 according to the third embodiment will be described below. First, an information recording method will be described. In the information storage device 16 having the above-described configuration, the information recording medium 1 can be locally heated by the laser light irradiated to the information recording medium 1 from the light irradiation unit 12. Information is written in the information recording medium 1 by applying a recording magnetic field for writing to the locally heated portion by the magnetic head 11.

  Details are as follows. First, at the time of recording, the information recording medium 1 is heated by laser light, and the medium temperature is locally raised to near the Curie temperature of the recording layer 8. The portion where the temperature is raised and reaches the vicinity of the Curie temperature is weakened in coercive force, the medium coercive force becomes smaller than the recording magnetic field applied to the information recording medium 1 from the magnetic head 11, and writing into the information recording medium 1 is performed. Is possible.

  At this time, the second backing layer 4 has magnetization in the in-plane direction of the substrate 2, and similarly functions as a backing layer together with the first backing layer 3 having magnetization in the in-plane direction of the substrate 2. At the time of signal recording, the recording magnetic field generated from the magnetic head 11 is induced to the second backing layer 4 and then to the first backing layer 3 having a higher magnetic permeability. The recording magnetic field induced into the first backing layer 3 then passes through the first backing layer 3 and forms a magnetic closed circuit that returns to the magnetic head 11 again. That is, at the time of signal recording, the intensity and gradient of the recording magnetic field can be increased, and the recording resolution of the information recording medium 1 can be improved.

  Next, a method for reproducing information will be described. Information reproduction is performed by detecting, with the magnetic head 11, the leakage magnetic field from the recording layer 8 on the information recorded as the magnetization direction on the recording layer 8 of the information recording medium 1. In the information storage device 16, the reproduction temperature of magnetization information was room temperature (about 30 ° C.).

  Here, as described in the first embodiment, at the time of signal reproduction, the second backing layer 4 exhibits an antiferromagnetic magnetization state, the total magnetization amount is zero, and no leakage magnetic flux is generated. It plays a layered role. That is, during signal reproduction, the spacing between the magnetic head 11 and the backing layer increases, and as a result, the leakage magnetic flux from the first backing layer 3 detected by the magnetic head 11 decreases. As described above, this occurs because the strength of the leakage magnetic flux attenuates in inverse proportion to the cube of the distance. Therefore, in the information recording medium 1 of the first embodiment of the present invention, noise due to leakage magnetic flux from the first backing layer 3 is reduced during signal reproduction.

  As described above, by combining the second backing layer 4 and the first backing layer 3 as the backing layer, it is possible to provide the information storage device 16 having excellent recording and reproducing characteristics.

  In the information recording medium 1, information can be reproduced using the polar Kerr effect. When the polar Kerr effect is used, laser light is used for reproducing information, and the deviation of the polarization plane between the incident light on the information recording medium 1 and the reflected light from the information recording medium 1 This is done by reading the difference in the amount of light with the light receiving element. When the polar magnetic Kerr effect is used, the protective layer 8 of the information recording medium 1 is preferably a transparent dielectric thin film such as AlN or SiN, and the lubricating layer 10 may not be provided.

  In the third embodiment, laser light is used as a means for locally heating the information recording medium 1. However, any laser that can heat the information recording medium 1 locally can be used. It is not limited to light.

  In the present embodiment, the method of locally heating the information recording medium 1 is used. However, a method of locally cooling the information recording medium 1 to change the magnetic characteristics of the information recording medium 1 may be used.

  11 and 12, the magnetic head 11 and the light irradiation unit 12 are described as an integrated recording / reproducing head. However, the magnetic head 11 and the light irradiation unit 12 may be separated from each other. In that case, in the information storage device 16, the magnetic head 11 and the light irradiation unit 12 may be driven separately, or the magnetic head 11 and the light irradiation unit 12 may be driven by one driving unit. .

  As described above, the information storage device 16 as the third embodiment of the present invention has been described using the information recording medium 1 according to the first embodiment of the present invention, but the information according to the second embodiment of the present invention is described. The recording medium 19 can also be used. Further, the information recording media 1 and 19 according to the present invention can be used in an information recording apparatus that only records information, an information reproducing apparatus that only reproduces information, and an information storage apparatus that records and reproduces information. It is clear that is also applicable.

  The present invention has been specifically described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. Is possible.

  The information recording medium, the manufacturing method thereof, and the information storage device of the present invention can be provided with a backing layer to increase the strength and gradient of the recording magnetic field for writing into the recording layer during signal recording, and the recording density In addition, the noise generation due to the backing layer can be suppressed during signal reproduction, and the reproduction signal quality can be improved.

It is sectional drawing which shows 1st Embodiment which concerns on the information recording medium of this invention. It is sectional drawing which shows 2nd Embodiment based on the information recording medium of this invention. It is a graph which shows the magnetic characteristic of the recording layer of the information recording medium in the said 1st Embodiment. It is a graph which shows the magnetic characteristic at the time of the signal reproduction | regeneration of the 1st backing layer in the information recording medium which concerns on the said 1st Embodiment. It is a graph which shows the magnetic characteristic at the time of signal reproduction | regeneration of the 2nd backing layer in the information recording medium which concerns on the said 1st Embodiment. It is a graph which shows the magnetic characteristic at the time of the signal recording of the 1st backing layer in the information recording medium which concerns on the said 1st Embodiment. It is a graph which shows the magnetic characteristic at the time of signal recording of the 2nd backing layer in the information recording medium concerning the above-mentioned first embodiment. It is a perspective view by the atomic force microscope image of the surface shape of the sample A which is an uneven | corrugated layer of the information recording medium which concerns on the said 2nd Embodiment. It is a perspective view by the atomic force microscope image of the surface shape of the sample B which is an uneven | corrugated layer of the information recording medium which concerns on the said 2nd Embodiment. It is a perspective view by the atomic force microscope image of the surface shape of the sample C which is an uneven | corrugated layer of the information recording medium which concerns on the said 2nd Embodiment. It is a schematic front view of the information recording / reproducing apparatus which concerns on 3rd Embodiment of this invention provided with the said information recording medium. It is a block diagram of the information recording / reproducing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Information recording medium 2 Substrate 3 1st backing layer 4 2nd backing layer 5 Dielectric layer 6 Concavity and convexity layer 7 Nonmagnetic intermediate layer 8 Recording layer 9 Protective layer 10 Lubricating layer 11 Magnetic head 12 Light irradiation part 13 Information recording medium Driving unit 14 Recording / reproducing system driving unit 15 Recording / reproducing signal processing system 16 Information storage device 17 Control unit 18 Recording / reproducing head 19 Information recording medium

Claims (21)

At least a substrate, a recording layer, and a backing layer for concentrating the magnetic field used for recording information signals in the recording layer,
The backing layer is composed of a first backing layer made of a soft magnetic material, and the magnetization decreases when approaching the signal reproduction temperature formed on the first backing layer. And a second backing layer having a magnetization in a perpendicular direction,
An information recording medium, wherein a first backing layer, a second backing layer, and a recording layer are laminated in that order on a substrate.   2. The information recording medium according to claim 1, wherein the second backing layer is made of a ferrimagnetic material and has a compensation temperature that is substantially the same as the signal reproduction temperature.   3. The information recording medium according to claim 1, wherein the first backing layer and the second backing layer are in contact with each other.   4. The magnetic recording medium according to claim 1, wherein an average film thickness of the second backing layer is 5 nm or more and 100 nm or less. 5.   5. The alloy according to claim 1, wherein the second backing layer is an alloy containing at least one element selected from rare earth metal elements and at least one element selected from transition metal elements. 2. An information recording medium according to item 1.   6. The information recording medium according to claim 5, wherein the rare earth metal element is at least one of Gd and Ho.   The information recording medium according to claim 5 or 6, wherein the transition metal element is at least one selected from the group consisting of Fe, Co, and Ni.   The information recording medium according to any one of claims 1 to 7, wherein a nonmagnetic intermediate layer is provided between the second backing layer and the recording layer.   9. The information recording medium according to claim 8, wherein an average film thickness of the nonmagnetic intermediate layer is 5 nm or less. The nonmagnetic intermediate layer has a dielectric layer formed of a dielectric, and a concavo-convex layer formed in a concavo-convex shape on the dielectric layer,
The concavo-convex layer is provided so that the concavo-convex shape is in contact with the recording layer,
The information recording medium according to claim 8, wherein the recording layer has a concavo-convex shape at an interface with the concavo-convex layer.   The information recording medium according to claim 10, wherein the dielectric layer is formed of at least one of a nitride and an oxide.   The information recording medium according to claim 10, wherein the concavo-convex layer is formed of aluminum.   13. The information recording medium according to claim 10, wherein an average film thickness of the dielectric layer is 2 nm or less.   14. The information recording medium according to claim 10, wherein the uneven layer has an average film thickness of 3 nm or less.   The information recording medium according to any one of claims 10 to 14, wherein the uneven surface has an average surface roughness (Ra) of 0.6 nm or more and less than 1.5 nm.   16. The uneven layer according to claim 10, wherein an average diameter of protrusions of the uneven shape forming the uneven layer is less than 50 nm at the interface with the recording layer. The information recording medium described in 1. In a method for manufacturing an information recording medium comprising a substrate, a recording layer, a first backing layer, and a second backing layer, which are laminated in the order of the first backing layer, the second backing layer, and the recording layer,
A method of manufacturing an information recording medium comprising the step of forming the second backing layer of a ferrimagnetic material so as to have a compensation temperature that is substantially the same as the signal reproduction temperature of the information recording medium. . Further, the information recording medium includes a dielectric layer and an uneven layer between the second backing layer and the recording layer,
Forming a dielectric layer on the second backing layer;
Forming an uneven layer on the dielectric layer so as to have an uneven shape;
The method of manufacturing an information recording medium according to claim 17, further comprising: forming the recording layer on the concavo-convex layer so as to contact the concavo-convex shape of the concavo-convex layer. A light irradiation unit that performs light irradiation for locally heating the information recording medium according to any one of claims 1 to 16,
A magnetic head that magnetically reproduces an information signal with respect to the recording layer of the information recording medium;
The light irradiation unit is controlled to heat the information recording medium to the compensation temperature of the second backing layer of the information recording medium, and the second backing layer reaches the compensation temperature, An information storage device comprising: a control unit that controls the magnetic head so as to reproduce an information signal recorded on the recording layer. A light irradiation unit that performs light irradiation for locally heating the information recording medium according to any one of claims 1 to 16,
A magnetic head for magnetically recording and reproducing information signals with respect to the recording layer of the information recording medium;
In the state where the light irradiation unit is controlled to heat the information recording medium to the compensation temperature of the second backing layer of the information recording medium, and the second backing layer has reached the compensation temperature, The information signal recorded on the recording layer is reproduced, or the information is recorded on the recording layer in a state where the second backing layer reaches a temperature having magnetization in a direction perpendicular to the stacking direction of the information recording medium. And a control unit for controlling the magnetic head so as to write a signal. Furthermore, an information recording medium driving unit that rotationally drives the information recording medium,
A head driving unit for driving the light irradiation unit and the magnetic head;
21. A signal processing unit that converts an information signal recorded on a recording layer of the information recording medium into a reproduction signal that can be reproduced by the information reproducing apparatus. Information storage device.

Images