JP2002092865A - Perpendicular magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium which simultaneously realizes an Mr/Ms ratio: around 1, the inclination of an MH curve: around 1/4π and has a high signal-to-noise ratio. SOLUTION: The perpendicular magnetic recording medium which has at least plural layers of ground surface layers and a perpendicular magnetic recording layer 4 approximately parallel in the direction of the axis of easy magnetization to the normal direction of the substrate on a substrate 1 is formed by laminating first ground surface layer 2 which consists of Ti or an alloy containing Ti, the second ground surface layer 3 which contains Cr and is formed on the first ground surface layer 2 and the perpendicular magnetic recording layer in this order. The second ground surface layer 3 includes at least one kind of additive elements among Pt, Ta, Nb, and Zr in the Co-base alloy containing Cr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a perpendicular magnetic recording medium. More specifically, the present invention relates to a configuration of a perpendicular magnetic recording medium capable of significantly reducing medium noise and obtaining a high S / N ratio, a method of manufacturing the same, and the like.

[0002]

2. Description of the Related Art With the recent increase in capacity of information processing, various information recording techniques have been developed. In particular, the areal recording density of hard disk drives using magnetic recording technology has been increasing at a rate of about 100% / year in recent years.
Naturally, in order to achieve a high areal recording density, it is essential to improve the performance of both a medium for recording information signals, a so-called magnetic recording medium, and a magnetic head for recording and reproducing information signals. is there. In particular, in order to improve the performance of a magnetic recording medium, that is, to secure a sufficient S / N ratio at a high areal recording density, the crystal grains of a ferromagnetic layer responsible for recording information signals are made finer and the layer is made finer. It is necessary to reduce the thickness. For example, in the case of a conventionally well-known longitudinal recording method, in order to achieve an areal recording density of 50 Gbit / inch ² level, an average crystal grain size: 6 to 7 nm,
Layer thickness: about 10 nm is required. In such a situation, there is a problem that thermal stability is lacked due to a so-called superparamagnetic phenomenon, which is an essential phenomenon accompanying the magnetic fine particles, and as a result, a recorded information signal is lost over time. appear.

[0003] Several methods have been proposed to overcome this problem, one of which is a perpendicular magnetic recording system. In other words, the perpendicular magnetic recording method has attracted attention as a method capable of achieving a sufficient S / N ratio while maintaining good thermal stability in a high surface recording density region. A recording medium used in a conventional perpendicular magnetic recording system will be described with reference to FIGS. FIG. 5 and FIG.
It is a schematic sectional view of a conventional perpendicular magnetic recording medium,
FIG. 5 shows a so-called single-layer perpendicular recording medium, and FIG. 6 shows a so-called two-layer perpendicular recording medium. In these figures, 51 and 61 are substrates made of glass or an Al alloy, etc., 52 is a crystal axis control layer made of a Ti or Ti alloy film, 53
And 64, a perpendicular magnetic recording layer made of a CoCrPt alloy film or the like; 54 and 65, a protective layer made of a C (carbon) film or the like; 62, a soft underlayer made of a CoNbZr amorphous alloy film; Layer 62 and perpendicular magnetic recording layer 64
And an intermediate layer for interrupting magnetic exchange coupling with the intermediate layer. As in the case of the longitudinal recording medium, the perpendicular magnetic recording layer is a polycrystalline material that is a set of fine crystal grains, and the average easy axis direction of the crystal grains is parallel to the normal to the substrate surface. The information signal is recorded as a change in the position of the magnetization direction of the perpendicular magnetic recording layer, and this is also the same as in the conventional longitudinal recording method. However, there is a difference described below regarding the magnetization direction in the recording state. That is, in the case of a perpendicular recording medium,
The average magnetization direction in the recording bit is the vertical direction with respect to the substrate surface, whereas in the case of a longitudinal recording medium, the average magnetization direction is the running direction of the recording head (not shown) or the opposite direction. Becomes The difference in the magnetization direction in this recording state is the reason that the above-described feature of the perpendicular magnetic recording system, that is, a sufficient S / N ratio can be achieved while maintaining good thermal stability (Reference: HNBertram and M. Wi.
lliams, “SNR and Density Limit Estimations: A Com
parison of Longitudinal and PerpendicularRecordin
g ”, IEEE Trans. Magn., vol. 36, pp4-9 (2000)).

[0004]

However, in the conventional perpendicular magnetic recording medium, the potential of the above-described perpendicular magnetic recording system could not be fully exploited due to problems in the magnetic characteristics. Hereinafter, a problem to be solved by the present invention, that is, a problem of the conventional perpendicular recording medium will be described with reference to FIGS.
FIG. 7 is a schematic diagram showing a microscopic structure of the perpendicular magnetic recording layer in a recording state. 7, reference numeral 71 denotes a perpendicular magnetic recording layer, 72 denotes crystal grains forming the perpendicular magnetic recording layer, 73 denotes a magnetization transition line, 74 and 75 denote arrows indicating an average magnetization direction in each recording bit, and 76 denotes each recording bit. Within
This is a reverse magnetic domain oriented in a direction different from the average magnetization direction. In general, it is known that noise sources in a perpendicular magnetic recording medium are due to irregular magnetization transition line shapes and generation of reverse magnetic domains. That is, when developing a medium having a high S / N ratio, it is important to minimize the frequency of occurrence of the magnetization transition line and the reverse magnetic domain with good linearity. In particular, in order to ensure the linearity of the magnetization transition line, it is indispensable to cut off magnetic exchange interaction acting between crystal grains. As described above, the essential points of the perpendicular magnetic recording layer required to bring out the excellent potential of the perpendicular magnetic recording system are as follows.
This is to suppress the generation of reverse magnetic domains and to cut off the intergranular exchange interaction.

[0005] Incidentally, the microscopic phenomenon described above,
The frequency of occurrence of reverse magnetic domains and the magnitude of intergranular exchange interaction are
It is well known that the evaluation can be made based on the shape of an MH curve which is a macroscopic magnetic characteristic. FIG. 8 shows an MH curve of the conventional perpendicular magnetic recording layer 71. In FIG. 8, Hc indicates coercive force, Ms indicates saturation magnetization, and Mr indicates residual magnetization. That is, the frequency of occurrence of reverse magnetic domains can be estimated by the ratio of Mr / Ms (so-called Mr squareness ratio), and the magnitude of intergranular exchange interaction can be estimated by the slope of the MH curve at coercive force Hc. That is, the frequency of occurrence of reverse magnetic domains increases with a decrease in Mr / Ms, and the intergranular exchange interaction increases with an increase in the slope of the MH curve. When no reverse magnetic domain is generated and the intergranular exchange interaction is completely shut off, the Mr / Ms ratio is 1, which is the maximum value, and the slope of the MH curve at the coercive force Hc is 1 / 4π, which is the minimum value. CGS unit). That is, realizing these values is a guideline in developing a perpendicular recording medium.

However, in the conventional perpendicular recording medium, the medium has an Mr / Ms ratio of 0.6 to 0.7 and an inclination of the MH curve of about 1 / 4π, or the ratio of Mr / Ms is:
Only about 1, a medium having an MH curve slope: 3 / 4π or more was obtained, and at the same time, an Mr / Ms ratio of 1, and an MH curve slope: 1 / 4π could not be realized.

An object of the present invention is to provide a ratio of Mr / Ms of 1, MH
An object of the present invention is to provide a perpendicular magnetic recording medium having a high S / N by simultaneously realizing a slope of a curve: 1 / 4π.

[0008]

In view of the above situation of perpendicular recording media, the present inventors have conducted various studies on the relationship between the medium structure and macroscopic and microscopic magnetic characteristics. It has been found that the perpendicular magnetic recording medium can simultaneously realize an Mr / Ms ratio of around 1: and an inclination of the MH curve of around 1 / 4π.
The present invention was found to be suitable as a technique for simultaneously realizing around 1 and the slope of the MH curve: around 1 / 4π, and completed the present invention.

The present invention has the following configuration.

(Structure 1) At least one underlayer for controlling the crystal axis of a magnetic recording layer on a substrate, and perpendicular magnetic recording on the underlayer, wherein the direction of the easy axis of magnetization is substantially parallel to the normal to the substrate surface. In a perpendicular magnetic recording medium having at least a layer, the perpendicular magnetic recording layer has a ratio of Mr / Ms = 0.9 to
1, and the slope of the MH curve at the holding force Hc is CGS
A perpendicular magnetic recording medium having a characteristic of 1 / 4π to 1.3 / 4π in a unit system.

(Structure 2) At least one underlayer for controlling the orientation of a magnetic recording layer on a substrate, and perpendicular magnetic recording on the underlayer in which the direction of the axis of easy magnetization is substantially parallel to the normal to the substrate surface. In the perpendicular magnetic recording medium having at least a layer, the underlayer includes a first underlayer made of Ti or an alloy containing Ti, a second underlayer containing Cr formed on the first underlayer, and The magnetic recording layer is made of a Co-based alloy in which Cr is segregated at grain boundaries, and the second underlayer is
Pt, Ta, Nb, and Zr are added to a Co-based alloy containing Cr.
A perpendicular magnetic recording medium comprising at least one additional element among the following.

(Structure 3) The second underlayer has a thickness of 15 at.
% Of Cr and a total of 15 at% or less of the Co element-containing alloy containing the additive element. The second underlayer has a hexagonal close-packed crystal structure, and its c-axis is in a direction normal to the substrate surface. 3. The perpendicular magnetic recording medium according to Configuration 2, wherein the perpendicular magnetic recording medium is substantially parallel to.

(Structure 4) The perpendicular magnetic recording medium according to Structure 1, wherein the perpendicular magnetic recording layer is made of a Co-based alloy containing at least Cr and Pt.

(Structure 5) The perpendicular magnetic recording medium according to Structure 4, wherein the perpendicular magnetic recording layer contains at least one of Ta, B, Nb, and Zr as an additive element.

(Structure 6) The structure 1 wherein the first underlayer and / or the second underlayer contains nitrogen.
5. The perpendicular magnetic recording medium according to one selected from No. 5.

(Structure 7) In the method for manufacturing a perpendicular magnetic recording medium according to Structures 2 to 6, a step of sequentially forming a first underlayer, a second underlayer, and a perpendicular magnetic recording layer on a substrate is provided. And a step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer.

(Structure 8) The step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer is a step of heat-treating the perpendicular magnetic recording layer at a temperature of 450 ° C. or more and 600 ° C. or less. 8. The method for manufacturing a perpendicular magnetic recording medium according to the seventh aspect.

[0018]

According to the first aspect, in the perpendicular magnetic recording medium having the film configuration according to the first aspect, the perpendicular magnetic recording layer has a Mr / M
It defines a perpendicular magnetic recording medium having a characteristic in which s = 0.9 to 1, and the slope of the MH curve at the coercive force Hc is 1 / 4π to 1.3 / 4π in the CGS unit system. Wherein the perpendicular magnetic recording layer has a ratio of Mr / Ms = 0.9 to 1 and an inclination of an MH curve at a coercive force Hc of 1 / 4π to 1 in a CGS unit system. .
Perpendicular magnetic recording media that does not have the property of being 3 / 4π are outside the scope of Configuration 1. According to the configuration 1, it is possible to simultaneously realize the Mr / Ms ratio of about 1 and the slope of the MH curve at the coercive force Hc of about 1 / 4π (CGS unit system), which cannot be realized by the conventional perpendicular magnetic recording medium. Therefore, it is possible to provide a medium having a high S / N ratio in which noise is significantly reduced, and the contribution to the improvement in recording density is extremely large. Mr / Ms is less than 0.9, or the slope of the MH curve at holding force Hc is 1.3 / 4π (CGS unit system)
If it exceeds, the effect of reducing noise is not sufficient. When the perpendicular magnetic recording layer has Mr / Ms = 0.97-1 and a coercive force H
The slope of the MH curve at c is from 1 / 4π in CGS unit system.
A perpendicular magnetic recording medium having a characteristic of 1.2 / 4π is more preferable, and further preferably 1 / 4π to 1.1 / 4π.
It is.

Configuration 2 shows an example of specific means for obtaining the characteristics described in Configuration 1. This will be described with reference to FIG. In the figure, 1 is a substrate, 2 is a first underlayer made of Ti or an alloy containing Ti, and 3 is at least Ta, N
The second underlayer made of a CoCr nonmagnetic alloy containing one of b, Zr, and Pt as an additional element,
This is a perpendicular magnetic recording layer made of an oCrPt-based ferromagnetic alloy. After forming a multilayer film having this configuration, for example, 450 to 60
By performing a heat treatment at 0 ° C. or the like, the ratio of Mr / Ms: 0.
9 to 1, the slope of the MH curve: 1 / 4π to 1.3 / 4π can be simultaneously realized. The required heat treatment time depends on the heat treatment temperature. For example, when the temperature is 500 ° C.,
About 20 minutes. Here, from the shape of the MH curve shown in FIG. 8, the ratio of Mr / Ms is around 1, and the slope of the MH curve is １ ／.
It can be easily inferred that a method of increasing the coercive force Hc is effective for simultaneously realizing the vicinity of π. Generally, in order to increase the coercive force, it is necessary to increase the magnetic anisotropy energy of the perpendicular magnetic recording layer, and the anisotropy energy of the CoCrPt-based alloy increases as the Pt concentration increases. It is known to Furthermore, as the Pt concentration increases, the grain boundary segregation of Cr is impaired, and as a result, the intergranular exchange interaction increases, and M
Although the r / Ms ratio asymptotically approaches 1, the slope of the MH curve is 1
It is also a well-known fact that it is much larger than / 4π. In the invention described in the configuration 2, the Cr is diffused and supplied mainly to the crystal grain boundaries of the perpendicular magnetic recording layer 4 from the second underlayer 3 shown in FIG. The purpose is to segregate the Cr at the grain boundaries to block intergranular exchange interaction. Such a method is a well-known fact and has no novelty.
The reason for the invention according to the second aspect is that when a CoCr alloy is used as the second underlayer 3, Ta, Zr,
By adding at least one of Nb and Pt, the diffusion efficiency of Cr is improved, and as a result, Mr / Ms
Ratio: 0.9 to 1, MH curve slope: 1 / 4π to 1.3 /
It has been found that this is an effective means for simultaneously realizing 4π. In the present invention, the first underlayer is
In addition to the crystal axis control function, the second
It has a function of promoting the diffusion of Cr from the second underlayer to the recording layer by interaction with the underlayer.

According to the third aspect, the second underlayer has a thickness of 15 at.
% Or more of Cr and an additional element having a total amount of 15 at% or less (T
a, Zr, Nb, and Pt) and a Co-based alloy containing Co (mainly a Co-based alloy). The second underlayer has a hexagonal close-packed crystal structure. Due to the structure and the c-axis thereof is substantially parallel to the normal direction of the substrate surface, the characteristics described in Configuration 1 can be reliably obtained. It is more preferable that the second underlayer is made of a Co-based alloy containing Cr at 20 at% or more and 40 at% or less, and Ta at 1 at% to 5 at% as one of the additional elements. Here, the presence of Ta significantly promotes the diffusion of Cr into the recording layer. As the additive element in the second underlayer, Ta or both Ta and Pt are more preferably added. In order to obtain the second underlayer as described above, a target composition of 25 at
% Of Cr and a total of 15 at% or less of a Co-based alloy target containing an additional element having a total amount of 15 at% or less, more preferably 25 to 40 at% or more of Cr, and 1 at% of Ta as one of the additional elements. 5a
It is preferable to include t% or less.

In each configuration of the present invention, when the first underlayer is a Ti layer, the first underlayer made of Ti has a hexagonal close-packed crystal structure, and It is preferable that the c-axis is substantially parallel to the normal direction of the substrate surface. In each configuration of the present invention,
When the first underlayer is an alloy layer containing Ti,
The first underlayer made of the alloy containing Ti includes Cr and C
o and at least 85 at% of Ti
It is preferable that the above-mentioned Ti-based alloy is used, the crystal structure of the first underlayer is a hexagonal close-packed structure, and the c-axis is substantially parallel to the normal direction of the substrate surface.

According to the fourth aspect, since the perpendicular magnetic recording layer is made of a Co-based alloy containing at least Cr and Pt, the characteristics described in the first aspect can be reliably obtained and high magnetic properties can be obtained. Can be. In this case, from the viewpoint of the magnetic anisotropy energy of the perpendicular magnetic recording layer, the Co content and the Pt in
More preferably, the total content is 78 at% or more, and the Pt content is 10 at% or more. The total of the Co content and the Pt content is 82 at% or more, and the Pt content is 11 at% or more. It is more preferable if there is. More specifically, an alloy target composition such as Co72at
%: Cr 15 at%: Pt 13 at% composition, Co73
A composition of at%: Cr 16 at%: Pt 11 at% is preferable.

According to the fifth aspect, the perpendicular magnetic recording layer is made of a Co-based alloy containing at least Cr and Pt, and contains at least one of Ta, B, Nb, and Zr as an additive element. The described characteristics can be reliably obtained, and the magnetic particles in the perpendicular magnetic recording layer are miniaturized, so that a higher S / N ratio can be obtained.
In this case, the total content of the additional elements is 1 at% or more and 6 a
It is more preferably at most t%.

According to the sixth aspect, the first underlayer and / or the second underlayer contain nitrogen by a method such as forming by a sputtering method in an Ar atmosphere containing nitrogen. It is preferable because the average particle diameter of the magnetic particles can be reduced, and as a result, a high S / N ratio can be obtained. In this case, it is more preferable that both the first underlayer and the second underlayer are formed by a sputtering method using an Ar atmosphere containing nitrogen. A containing nitrogen
As the atmosphere, the nitrogen partial pressure ratio in the total gas pressure is 0.05
It is more preferable that the value be at least 0.4 and at most 0.4.

According to the seventh aspect, in the method of manufacturing a perpendicular magnetic recording medium according to the second to sixth aspects, the method further includes a step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer. Can be obtained in a perpendicular magnetic recording medium layer in which particles are segregated at grain boundaries. As a step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer, for example, a method of heat-treating the perpendicular magnetic recording layer, or forming the perpendicular magnetic recording layer by sputtering at a high temperature (for example, 150 to 450 ° C.) Method. By the step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer, for example, in the case of heat treatment, the rate of increase of Cr in the perpendicular magnetic recording layer before and after heat treatment ｛[(Cr content after heat treatment (at %) / (Cr content before heat treatment (at%)]-1} × 100 is preferably 10% or more, preferably 30% or more, and most preferably 50% or more.

According to the eighth aspect, in the seventh aspect, since the perpendicular magnetic recording layer is a film heat-treated at a temperature of 450 ° C. or more and 600 ° C. or less, the characteristics described in the first aspect can be reliably obtained. it can. Here, at 400 ° C. or lower, there is no heat treatment effect, which is the same as not performing heat treatment.
When the temperature exceeds ℃, the segregation of Cr disappears and the magnetic properties such as the coercive force Hc deteriorate. From 400 ° C. to 450 ° C., the effect of the heat treatment sharply increases, but the diffusion of Cr and the segregation of Cr are insufficient. Although the optimum temperature of the heat treatment cannot be unconditionally determined because it varies depending on the film configuration, 450 ° C. to 550 ° C. is more preferable.
A temperature around 500 ° C. is most preferred. In the configuration 8, the first
It is preferable that the underlayer, the second underlayer, the perpendicular magnetic recording layer, and the like are sequentially formed at room temperature and then heat-treated at the above-mentioned predetermined temperature.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. However, the following is merely an embodiment of the present invention and does not limit the technical scope of the present invention. It does not do. (Embodiment 1) A first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic sectional view of a magnetic recording medium according to one embodiment of the present invention. In the figure, 11 is a disk-shaped glass substrate (disk substrate), 12 is a first underlayer made of Ti, 13 is a second underlayer made of a CoCrTa alloy film, 1
4 is a perpendicular magnetic recording layer made of a CoCrPt alloy film;
Is a protective layer made of C (carbon). The thickness of the first underlayer made of Ti is 25 nm, the thickness of the second underlayer made of a CoCrTa alloy film is 20 nm, and the thickness of CoCrPt is 20 nm.
The thickness of the perpendicular magnetic recording layer made of an alloy film is 40 nm, and the thickness of the protective layer made of C is 5 nm. Hereinafter, a method for manufacturing a magnetic recording medium having the above film configuration will be described. First, a first underlayer 12 made of Ti was formed on a substrate 11 by RF sputtering in a pure Ar atmosphere (at room temperature). Thereafter, similarly, a CoCrTa alloy target (Co: 65a
t%, Cr: 32at%, Ta: 3at%)
A second underlayer made of a Ta alloy film is formed, and then a CoCrPt alloy target (Co: 72 at%, C
r: 15at%, Pt: 13at%) to obtain CoCrPt
The perpendicular magnetic recording layers 14 made of an alloy film were sequentially formed (film formation at room temperature). Next, a heat treatment was performed at 500 ° C. for about 20 minutes in a vacuum furnace having an ultimate vacuum of 1 × 10 ⁻⁵ Torr or less to form a protective layer 15 made of C. Next, the crystal orientation characteristics of the perpendicular magnetic recording medium obtained as described above were examined with an X-ray diffractometer. As a result, it was confirmed that the perpendicular magnetic recording layer composed of the CoCrPt alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) was about 3 °. Also, CoCr
It was confirmed that the second underlayer made of the Ta alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) was also about 3 °. Next, Co of the perpendicular magnetic recording medium obtained above
The average particle size of the perpendicular magnetic recording layer made of a CrPt alloy film was examined by a transmission electron microscope. As a result, the average particle size was about 14 nm. The composition of the perpendicular magnetic recording layer was analyzed by ESCA.
o: 74.5 at%, Cr: 12.7 at%, Pt: 1
The composition after the heat treatment was Co: 69.7 at 1.9 at%.
at%, Cr: 19.4 at%, Pt: 10.9 at%
The Cr increase rate was 53%, and the Cr increased after the heat treatment, indicating that Cr of the second underlayer was supplied to the perpendicular magnetic recording layer. Next, the macroscopic magnetic characteristics (MH curve) of the perpendicular magnetic recording medium obtained as described above were measured with a vibrating sample magnetometer (VSM). The Mr / Ms ratio obtained from the MH curve was 0.98, and the slope of the MH curve at the holding force Hc was 1.2 / 4π (CGS unit system). The recording / reproducing characteristics of the perpendicular magnetic recording medium of the present invention obtained as described above are shown by the macroscopic magnetic characteristics of Mr / Ms ratio:
0.6, slope of MH curve at holding force Hc: 1.1 /
The recording / reproducing characteristics of a conventional perpendicular magnetic recording medium of 4π (CGS unit system) were compared. As a result, the S / N is about 5 dB
Increased. Further, as a comparative example, the Cr increase rate was measured for a perpendicular magnetic recording medium manufactured in the same manner as in Example 1 except that the target composition of the second underlayer was Co: 65 at% and Cr: 35 at%. 1.6%.

(Embodiment 2) A second embodiment of the present invention will be described. The basic layer configuration of the second embodiment is the same as that of the first embodiment, and will be described with reference to FIG. FIG.
Among them, 11 is a disk-shaped glass substrate, 12 is a first underlayer made of a TiCo alloy film, 13 is a second underlayer made of a CoCrTa alloy film, 14 is a perpendicular magnetic recording layer made of a CoCrPt alloy film, and 15 is C. It is a protective layer. Note that Ti
The first underlayer made of a Co alloy film has a thickness of 25 nm,
The thickness of the second underlayer made of the CrTa alloy film is 20 nm,
The thickness of the perpendicular magnetic recording layer made of a CoCrPt alloy film is 4
The thickness of the protective layer made of 0 nm and C is 5 nm. Hereinafter, a method for manufacturing a magnetic recording medium having the above film configuration will be described. First, a TiCo alloy target (Ti: 9
(0 at%, Co: 10 at%) by sputtering to form a first underlayer 12 made of a TiCo alloy film (film formation at room temperature). Thereafter, a CoCrTa alloy target (Co: 65 at%, Cr: 32 at%, T:
a: 3 at%) to form a second underlayer 13 made of a CoCrTa alloy film (film formation at room temperature).
CrPt alloy target (Co: 72at%, Cr: 15at%, Pt: 13at
%) To form a perpendicular magnetic recording layer 14 of a CoCrPt alloy film (film formation at room temperature). Next, in a vacuum furnace with an ultimate vacuum of 1 × 10 ⁻⁵ Torr or less, for approximately 20 minutes.
A heat treatment at 500 ° C. was performed to form a protective layer 15 made of C. Next, the crystal orientation characteristics of the perpendicular magnetic recording medium obtained as described above were examined with an X-ray diffractometer. as a result,
It was confirmed that the first underlayer made of the TiCo alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) is about 3.
5 °. Also, a second layer made of a CoCrTa alloy film is used.
It was confirmed that the underlayer had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) was also about 2.9 °. Also, CoC
It was confirmed that the perpendicular magnetic recording layer made of the rPt alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) was about 2.9 °. Next, the average particle diameter of the perpendicular magnetic recording layer made of the CoCrPt alloy film of the perpendicular magnetic recording medium obtained as described above was examined with a transmission electron microscope. As a result, the average particle size was about 13 nm. Next, the macroscopic magnetic characteristics (MH) of the perpendicular magnetic recording medium obtained above
Curve) was measured with a vibrating sample magnetometer (VSM). M
The Mr / Ms ratio obtained from the H curve is 0.99, and the holding force H
The slope of the MH curve at c was 1.2 / 4π (CGS unit system). The recording / reproducing characteristics of the perpendicular magnetic recording medium of the present invention obtained as described above indicate that the macroscopic magnetic characteristics are Mr /
Ms ratio: 0.6, slope of MH curve at holding force Hc:
The recording / reproducing characteristics of the conventional perpendicular magnetic recording medium, which is 1.1 / 4π (CGS unit system), were compared. As a result, the S / N increased about 6 dB.

(Embodiment 3) A third embodiment of the present invention will be described. The basic layer configuration of the third embodiment is the same as that of the first embodiment, and will be described with reference to FIG. FIG.
In the figure, 11 is a disk-shaped glass substrate, and 12 is a first glass substrate.
An underlayer, 13 is a second underlayer made of a CoCrTa alloy film, 14 is a perpendicular magnetic recording layer made of a CoCrPtB alloy film, and 15 is a protective layer made of C. The thickness of the first underlayer made of Ti is 25 nm, the thickness of the second underlayer made of the CoCrTa alloy film is 20 nm, the thickness of the perpendicular magnetic recording layer made of the CoCrPtB alloy film is 40 nm, and the protective layer made of C is Is 5 nm. Hereinafter, a method for manufacturing a magnetic recording medium having the above film configuration will be described. First, a first underlayer 12 made of Ti was formed on a substrate 11 by RF sputtering in a pure Ar atmosphere (at room temperature). Thereafter, similarly, a CoCrTa alloy target (Co: 65a
t%, Cr: 32at%, Ta: 3at%)
Formation of second underlayer 13 made of Ta alloy film (film formation at room temperature)
Then, a CoCrPtB alloy target (Co: 71 at%, C
r: 13at%, Pt: 12at%, B: 4at%)
A perpendicular magnetic recording layer 14 made of a CrPtB alloy film was formed (formed at room temperature). Next, the ultimate vacuum degree is 1 × 10 ⁻⁵ Torr
Perform a heat treatment at 500 ° C. for about 20 minutes in the following vacuum furnace,
A protective layer 15 made of C was formed. Next, the crystal orientation characteristics of the perpendicular magnetic recording medium obtained as described above were examined with an X-ray diffractometer. As a result, the perpendicular magnetic recording layer made of the CoCrPtB alloy film has a hexagonal close-packed structure,
It was confirmed that the axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) was about 3 °. In addition, it was confirmed that the second underlayer made of the CoCrTa alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. Dispersion of the degree of orientation (Δθ ₅₀ )
Was also about 3 °. Next, the macroscopic magnetic characteristics (MH curve) of the perpendicular magnetic recording medium obtained as described above were measured with a vibrating sample magnetometer (VSM). M obtained from the MH curve
The r / Ms ratio was 0.97, and the slope of the MH curve at the holding force Hc was 1.1 / 4π (CGS unit system). Next, the CoCrPtB of the perpendicular magnetic recording medium obtained above was used.
The average particle diameter of the perpendicular magnetic recording layer made of an alloy film was examined by a transmission electron microscope. As a result, the average particle size was about 7 nm. The recording / reproducing characteristics of the perpendicular magnetic recording medium of the present invention obtained as described above indicate that the macroscopic magnetic characteristics are Mr /
Ms ratio: 0.6, slope of MH curve at holding force Hc:
The recording / reproducing characteristics of the conventional perpendicular magnetic recording medium, which is 1.1 / 4π (CGS unit system), were compared. As a result, the S / N increased by about 7.5 dB. As described above, the magnetic recording layer in which the perpendicular magnetic recording layer is laminated on the non-magnetic alloy layer containing Cr and the non-magnetic alloy layer containing Cr is laminated on Ti or an alloy layer containing Ti. In the medium, the perpendicular magnetic recording layer is a thin film made of a Co-based alloy containing at least Cr and Pt, and Ta,
By including at least one of B, Nb, and Zr and setting the content of the additional element to 10 at% or less (preferably 1 to 6 at%), the particle diameter of the perpendicular magnetic recording layer can be reduced. As a result, a high S / N can be obtained.

(Embodiment 4) A fourth embodiment of the present invention will be described. The basic layer configuration of the fourth embodiment is the same as that of the first embodiment, and will be described with reference to FIG. FIG.
In the figure, 11 is a disk-shaped glass substrate, and 12 is a first glass substrate.
An underlayer, 13 is a second underlayer made of a CoCrTa alloy film, 14 is a perpendicular magnetic recording layer made of a CoCrPt alloy film, and 15 is a protective layer made of C. The thickness of the first underlayer made of Ti is 25 nm, the thickness of the second underlayer made of the CoCrTa alloy film is 20 nm, the thickness of the perpendicular magnetic recording layer made of the CoCrPt alloy film is 40 nm, and the protective layer made of C is formed. Is 5 nm. Hereinafter, a method for manufacturing a magnetic recording medium having the above film configuration will be described. First,
The first underlayer 12 made of Ti was formed on the substrate 11 by RF sputtering in an atmosphere in which the partial pressure ratio of Ar and N ₂ was 10: 1 (film formation at room temperature). Thereafter, similarly, a CoCrTa alloy target (Co: 65 at%, Cr: 32) was formed by an RF sputtering method in an atmosphere in which the partial pressure ratio of Ar and N ₂ was 10: 1.
(at%, Ta: 3 at%) was sputtered to form a second underlayer 13 made of a CoCrTa alloy film (film formation at room temperature). Then, a CoCrPt alloy target (Co: 72 at%, Cr: 15 at%, Pt: 1) was produced by RF sputtering in a pure Ar atmosphere.
3 at%) to form a perpendicular magnetic recording layer 14 of a CoCrPt alloy film (film formation at room temperature). Next, in a vacuum furnace having an ultimate vacuum of 1 × 10 ⁻⁵ Torr or less, approximately 20
A heat treatment at 500 ° C. was performed for a minute to form a protective layer 15 made of C. Next, the crystal orientation characteristics of the perpendicular magnetic recording medium obtained as described above were examined with an X-ray diffractometer. As a result, it was confirmed that the perpendicular magnetic recording layer composed of the CoCrPt alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ
₅₀ ) was about 3 °. In addition, it was confirmed that the second underlayer made of the CoCrTa alloy film had a hexagonal close-packed structure, and that the c-axis was substantially oriented in the normal direction of the substrate surface. The dispersion of the degree of orientation (Δθ ₅₀ ) was also about 3 °. Next, the average particle diameter of the perpendicular magnetic recording layer made of the CoCrPt alloy film of the perpendicular magnetic recording medium obtained as described above was examined with a transmission electron microscope. As a result, the average particle size was about 8 nm.
Met. Next, the macroscopic magnetic characteristics (MH curve) of the perpendicular magnetic recording medium obtained above were measured using a vibrating sample magnetometer (VS
M). Mr / Ms obtained from MH curve
The ratio is 0.98, and the slope of the MH curve at the holding force Hc is:
1.2 / 4π (CGS unit system). The recording / reproducing characteristics of the perpendicular magnetic recording medium of the present invention obtained as described above are as follows. The macroscopic magnetic characteristics are as follows: Mr / Ms ratio: 0.6, slope of MH curve at holding force Hc: 1.1 / 4π (CGS unit) system)
Of the conventional perpendicular magnetic recording medium. As a result, the S / N increased by about 7.5 dB. Thus, the perpendicular magnetic recording layer is laminated on the non-magnetic alloy layer containing Cr, and the non-magnetic alloy layer containing Cr is
In a magnetic recording medium laminated on an alloy layer containing i or Ti, a non-magnetic alloy layer containing Cr,
By sputtering at least one of the alloy layers containing i or Ti in an Ar atmosphere containing nitrogen, the particle diameter of the perpendicular magnetic recording layer is reduced, and as a result, a high S / N can be obtained. .

(Embodiment 5)
The target composition used for producing the perpendicular magnetic recording layer made of a Pt alloy film is the same as that of Example 1 with Co: 72 at%, Cr: 15 at%, and Pt: 13 at%, and the first underlayer layer made of Ti The thickness was changed as shown in FIG. 3, and the target composition of the second underlayer was Co: 65 at%, Cr: 32 at%, Ta: 3 at% (same as in Example 1), Co: 65 at%, Cr: The magnetic properties of the perpendicular magnetic recording layer before and after the heat treatment were examined for two types of 35 at% (same as the comparison).
The result is shown in FIG. In FIG. 3, in FIG.
/ Ms ratio: 0.09, slope of MH curve at holding force Hc: 2.7 / 4π (CGS unit system). In (b), the ratio of Mr / Ms is 0.09, and the slope of the MH curve at the holding force Hc is 2.6 / 4π (CGS unit system). (C)
Then, the ratio of Mr / Ms: 0.37, MH at the holding force Hc
Curve slope: 2.8 / 4π (CGS unit system).
In (d), the ratio of Mr / Ms is 0.9, and the slope of the MH curve at the holding force Hc is 1.3 / 4π (CGS unit system). (E), Mr / Ms ratio: 0.96, slope of MH curve at holding force Hc: 1.3 / 4π (CGS unit system)
It is. (F): Mr / Ms ratio: 0.98, holding force H
The slope of the MH curve at c: 1.2 / 4π (CGS unit system). As is clear from FIGS. 3 (a) to 3 (c),
CoCr alloy film containing no additional components (Co: 65at%, Cr: 35at
%), The magnetic properties are poor and at the same level as the conventional case. In contrast, FIG.
As is clear from (d) to (f), a CoCr alloy film (Co: 65 at%, Cr: 32 at%, Ta: 3
at%), the thickness of the first underlayer made of Ti is set to 15 to 25 nm.
Ratio: 0.9 to 1, slope of MH curve at holding force Hc:
1 / 4π to 1.3 / 4π (CGS unit system) can be achieved,
The magnetic properties are also good. Particularly good results are obtained when the thickness of the first underlayer made of Ti is 15 to 25 nm. In addition, as a result of changing the thickness of the first underlayer made of Ti in the range of 5 to 30 nm in the film configuration and the heat treatment conditions of the present example, it was found that the range of 15 to 25 nm was preferable. Similarly, under the film configuration and heat treatment conditions of the present embodiment, CoCr containing the predetermined additive component of the present invention is used.
As a result of changing the thickness of the second underlayer made of the alloy film in the range of 5 to 30 nm, the range of 15 to 25 nm is preferable,
It turned out that the vicinity of 20 nm is most preferable.

(Embodiment 6) In Embodiment 1, CoCr
The target composition used for producing the perpendicular magnetic recording layer made of a Pt alloy film is the same as that of Example 1 with Co: 72 at%, Cr: 15 at%, and Pt: 13 at%, and the first underlayer layer made of Ti The thickness was changed as shown in FIG. 4, and the target composition of the second underlayer was Co: 60 at%, Cr: 30 at%, Pt: 8 at%, Ta: 2 at%, and the perpendicular magnetic recording layer before and after the heat treatment was changed. The film composition and the rate of increase of Cr in the perpendicular magnetic recording layer were examined. FIG. 4 shows the results. As is clear from FIG. 4, it can be seen that the greater the thickness of the first underlayer, the higher the effect of promoting Cr diffusion.

Although the embodiment has been described above, when Nb or Zr is used as an additive element of the perpendicular magnetic recording layer made of a Co-based alloy film, Pt is used as an additive element of the second underlayer made of the Co-based alloy film. When Nb or Zr is used, Ti is used as the first underlayer.
Similar results were obtained when a Cr alloy was used. In the heat treatment step in a vacuum furnace, the heat treatment temperature is 450 ° C., 550 ° C.
Similar results were obtained with treatment times of about 30 minutes and about 15 minutes, respectively.

The present invention is not limited to the above embodiment. For example, the first underlayer can be a multilayer film in which films having the same composition, slightly different compositions, or different compositions are stacked. Similarly, the second underlayer can be a multilayer film in which films of the same composition, slightly different compositions, or different compositions are stacked. The second underlayer can also be provided in the perpendicular magnetic recording layer. For example, the film configuration of the first underlayer / second underlayer / perpendicular magnetic recording layer / second underlayer / perpendicular magnetic recording layer from the substrate side It can be. The perpendicular magnetic recording layer can be a multilayer film having the same composition, a slightly different composition, or a laminate of films having different compositions.

The present invention can be applied to the above-described two-layer type perpendicular recording medium. More specifically, for example, the composition 2 of substrate / underlying soft magnetic layer / first underlayer / second underlayer / perpendicular magnetic recording layer
It can be a layered perpendicular recording medium. In the case of a two-layer type perpendicular recording medium, the thickness of the perpendicular magnetic recording layer tends to be reduced, and accordingly, the thicknesses of the first underlayer and the second underlayer within a range where the effects of the present invention can be effectively exhibited. Is preferably reduced. For the soft magnetic underlayer, NiFe, CoN
bZr amorphous alloy film and the like.

In the perpendicular magnetic recording medium of the present invention, a lubricating layer and other known layers can be provided. The substrate material is not limited to glass (including chemically strengthened glass and crystallized glass), and a well-known substrate material can be used.

[0037]

As described above, according to the present invention,
It is possible to provide a perpendicular magnetic recording medium having a ratio of Mr / Ms = 1, a slope of the MH curve at coercive force Hc = 1 / 4π (CGS unit system), and a high S / N. The contribution to improving the recording density is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view for explaining a perpendicular magnetic recording medium of the present invention.

FIG. 2 is a schematic sectional view showing a perpendicular magnetic recording medium according to one embodiment of the present invention.

FIG. 3 is a diagram showing an MH curve of a perpendicular magnetic recording layer in Example 5.

FIG. 4 is a diagram showing a composition, a Cr increasing rate, and the like of a perpendicular magnetic recording layer before and after heat treatment in Example 6.

FIG. 5 is a schematic sectional view of a conventional single-layer type perpendicular magnetic recording medium.

FIG. 6 is a schematic sectional view of a conventional two-layer perpendicular magnetic recording medium.

FIG. 7 is a schematic diagram showing a microscopic structure in a recording state of a perpendicular magnetic recording layer.

FIG. 8 is an MH curve of a conventional perpendicular magnetic recording layer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st underlayer 3 ... 2nd underlayer 4 ... Perpendicular magnetic recording layer 11 ... Glass substrate 12 ... 1st underlayer 13 ... 2nd underlayer 14 ... Perpendicular magnetic recording layer 15 ... Protective layer 51 ... Substrate 52: Crystal axis control layer 53: Perpendicular magnetic recording layer 54: Protective layer 61: Substrate 62: Underlying soft magnetic layer 63: Intermediate layer 64: Perpendicular magnetic recording layer 65: Protective layer 71: Perpendicular magnetic recording layer 72: Perpendicular magnetic recording Crystal grains forming layer 73: magnetization transition line 74: arrow representing average magnetization direction in each recording bit 75: arrow representing average magnetization direction in each recording bit 76: different from average magnetization direction in each recording bit Reverse domain facing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junta Nakano 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Inside Hoya Co., Ltd. No. 5 F-term in Hoya Corporation (reference) 5D006 BB02 BB06 BB07 CA01 CA05 CA06 DA03 DA08 5D112 AA03 AA05 AA11 AA24 BB05 BD03 BD04 BD07 BD08 FA04 GB03

Claims (8)

[Claims] At least one underlayer for controlling the crystal axis of a magnetic recording layer on a substrate, and a perpendicular magnetic recording layer on which an easy axis direction is substantially parallel to a substrate surface normal direction is formed on the underlayer. In the perpendicular magnetic recording medium having at least: the perpendicular magnetic recording layer has a ratio of Mr / Ms = 0.9 to 1 and an inclination of an MH curve in a coercive force Hc of 1 / 4π to 1.3 / 4π in a CGS unit system. A perpendicular magnetic recording medium having certain characteristics. 2. At least one underlayer for controlling the orientation of a magnetic recording layer on a substrate, and a perpendicular magnetic recording layer having an easy axis of magnetization substantially parallel to a normal to the substrate surface on the underlayer. In the perpendicular magnetic recording medium having at least, the underlayer includes a first underlayer made of Ti or an alloy containing Ti, and a second underlayer containing Cr formed on the first underlayer. The layer is made of a Co-based alloy in which Cr is segregated at the grain boundary, and the second underlayer is made of Pt, T
A perpendicular magnetic recording medium comprising at least one additional element of a, Nb, and Zr. 3. The method according to claim 2, wherein the second underlayer has a C content of 15 at% or more.
r and Co containing the additive element in a total amount of 15 at% or less.
3. The perpendicular magnetic field according to claim 2, wherein the second underlayer is made of a base alloy, the crystal structure of the second underlayer is a hexagonal close-packed structure, and the c-axis is substantially parallel to the normal direction of the substrate surface. recoding media. 4. The method according to claim 1, wherein the perpendicular magnetic recording layer comprises at least Cr.
4. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is made of a Co-based alloy containing Pt and Pt. 5. The perpendicular magnetic recording medium according to claim 4, wherein the perpendicular magnetic recording layer contains at least one of Ta, B, Nb, and Zr as an additional element. 6. The perpendicular magnetic recording medium according to claim 1, wherein the first underlayer and / or the second underlayer contains nitrogen. 7. A method for manufacturing a perpendicular magnetic recording medium according to claim 2, comprising a step of sequentially forming a first underlayer, a second underlayer, and a perpendicular magnetic recording layer on a substrate. And a step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer. 8. The method according to claim 1, wherein the step of diffusing and supplying Cr in the second underlayer into the perpendicular magnetic recording layer is a step of heat-treating the perpendicular magnetic recording layer at a temperature of 450 ° C. to 600 ° C. Item 8. The method for manufacturing a perpendicular magnetic recording medium according to Item 7.