JPH0532809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a perpendicular magnetic recording medium, and more particularly to a perpendicular magnetic recording medium capable of increasing recording and reproducing output.

BACKGROUND TECHNOLOGY In general, in order to record on and read from a magnetic recording medium using a magnetic head, the magnetic head is used to write information on the magnetic layer of the magnetic recording medium in the longitudinal direction (in-plane direction) of the medium.
A commonly used device is one that performs magnetization to record and reproduce this information. However, according to this method, it is known that as the recording density increases, the demagnetizing field increases and the demagnetizing effect has an adverse effect on high-density recording. Therefore, in recent years, a perpendicular magnetic recording method has been proposed in which the magnetic layer of a magnetic recording medium is magnetized in the perpendicular direction to eliminate the above-mentioned adverse effects. According to this, as the recording density is improved, the demagnetizing field becomes smaller, and theoretically, it is possible to perform good high-density recording without reducing residual magnetization.

Conventionally, perpendicular magnetic recording media used in this perpendicular magnetic recording system include those in which a Co--Cr film is formed on a base film by sputtering. As is well known, the Co-Cr film has a relatively high saturation magnetization (Ms) and an axis of easy magnetization perpendicular to the film surface (that is, the coercive force Hc⊥ in the direction perpendicular to the film surface is large). ), it is known to be an extremely promising material for perpendicular magnetic recording media. However, in the Co-Cr film, the easy axis of magnetization changes due to the addition of Cr (the C axis of a close-packed hexagonal system).
Although it has a nearly perpendicular orientation, it is not sufficiently oriented in the perpendicular direction and strong perpendicular magnetic anisotropy could not be obtained. For this reason, conventionally Co-Cr
There was a perpendicular magnetic recording medium in which the axis of easy magnetization of Co was strongly oriented in the perpendicular direction by adding a third element such as niobium (Nb) and tantalum (Ta) to Co. In addition, a high magnetic permeability layer (i.e., a layer with low coercive force Hc, e.g. Ni-Fe), which is a so-called backing layer, is formed separately between the Co-Cr film and the base film to create a two-layer structure. There is a perpendicular magnetic recording medium which is capable of producing strong perpendicular magnetization with a sharp distribution by concentrating the magnetic flux spreading within the magnetic head towards the magnetic pole of the magnetic head at a predetermined magnetic recording position and attracting it.

Problems to be Solved by the Invention In the conventional perpendicular magnetic recording medium described above, in order to strongly orient the axis of easy magnetization of Co in the perpendicular direction,
Cr, Nb, Ta, etc. were added to it. However,
Although the axis of easy magnetization of Co is strongly oriented in the perpendicular direction due to the addition of Cr, Nb, and Ta, it remains a ferromagnetic material.
Saturation magnetization as a perpendicular magnetic recording medium by adding non-magnetic materials Cr, Nb, and Ta to Co
There was a problem in that Ms decreased and high playback output could not be obtained. In addition, in the case of a two-layer perpendicular magnetic recording medium in which a high magnetic permeability layer is formed as a backing layer in addition to a Co-Cr film, the high magnetic permeability layer resists the coercive force Hc (700 Oe or more) of the Co-Cr film. Since the magnetic force Hc was extremely small (10 Oe or less), there was a problem in that it generated impulsive Barkhausen noise. In addition to this, at least 10Oe to prevent this Barkhausen noise
Although it is necessary to have the above coercive force, there is also the problem that there is no suitable material that satisfies this condition and functions as a backing layer.

Therefore, in the present invention, we focused on the fact that when coating a magnetic material made of cobalt and chromium with at least one of niobium and tantalum added, the magnetic layer is formed into two layers with different coercive forces,
It is an object of the present invention to provide a perpendicular magnetic recording medium that solves the above-mentioned problems by actively utilizing the small-grain crystal layer having a small internal coercive force in the two layers for perpendicular magnetic recording.

Means and Effects for Solving the Problems In order to solve the above problems, the present invention provides a magnetic material having a low coercive force on a base using a magnetic material made of cobalt and chromium and adding at least one of niobium and tantalum. A layer having a magnetization jump, which is an in-plane M-H hysteresis characteristic represented by a curve that rises sharply near the origin, is formed, and on the layer, niobium or tantalum is added in an amount smaller than the amount of niobium or tantalum added to the layer. A perpendicular magnetization layer was formed of a magnetic material in which at least one of niobium and tantalum was added to cobalt and chromium in an amount that would not cause a magnetization jump.

By taking each of the above measures, the perpendicularly magnetized layer that is perpendicularly magnetized and does not cause a magnetization jump can maintain a high saturation magnetization Ms, and the layer that has a low coercive force and a magnetization jump functions as a so-called underlayer.

Embodiment A perpendicular magnetic recording medium according to the present invention (hereinafter simply referred to as a recording medium) is first made of cobalt (Co), chromium (Cr), niobium (Nb), and tantalum (Ta) on a base polyimide substrate. Sputtering is performed using a magnetic material as a target to which Co and Cr are added, and then sputtering is performed using a magnetic material as a target on which Co and Cr are added and at least one of niobium (Nb) and tantalum (Ta) is added in a smaller amount than the above amount. It can be obtained by

Conventionally, when sputtering metal, etc. (e.g. Co-Cr alloy) onto a base, the thin film formed does not form the same crystal structure in the direction perpendicular to the film surface, but instead forms an extremely thin part near the base. Various experiments (e.g., scanning electron microscopy photography) have shown that a first crystal layer with small grain size is formed first, followed by a second crystal layer with large grain size. (Edward R.Wuori and Professor JHJudy:
“INITIAL LAYER EFFECT IN CO−CR
FILMS”, IEEE Trans., VOL.MAG−20, No.
5, SEPTEMBER 1984, P774-P775 or
William G. Haines: “VSM PROFILING OF
CoCr FILMS：A NEW ANALYTICAL
TECHNIQUE”IEEE Trans., VOL, MAG−
20, No. 5, SEPTEMBER 1984, P812-P814).

The present inventor focused on the above viewpoint and sputtered various metals based on a Co-Cr alloy and added with a third element, thereby forming a crystal layer with a small grain size and a large grain crystal layer formed on top of the crystal layer. As a result of measuring the physical properties of the diameter crystal layer, we found that Nb or
It was found that when Ta was added, the coercive force of the small-grain crystal layer was much smaller than that of the large-grain crystal layer, and there was no extreme difference in the coercive force in the vertical and in-plane directions. . In the present invention, a small-grain crystal layer having low coercive force and a small difference in coercive force in the perpendicular direction and in-plane direction is used as an isotropic layer, and the added amount of Nb and Ta is applied on this small-grain crystal layer. Co-Cr-Nb thin film or Co-Cr-Ta that has a low and high saturation magnetization Ms and has a strong axis of easy magnetization oriented in the perpendicular direction.
It is characterized by forming a thin film and using this as a perpendicular magnetic layer.

A small-grain crystal layer of a magnetic material containing at least one of Co, Cr, Nb, and Ta formed by sputtering performed by the present inventor;
The experimental results of measuring the coercive force of a large-grain crystal layer will be described in detail. Co-Cr thin film, Co-Cr-Nb thin film and Co-
When sputtering the Cr--Ta thin film, the sputtering conditions were set as follows (the sputtering conditions were set equally in each case where Nb or Ta was added).

*Sputtering equipment RF magnetron sputtering equipment *Sputtering method Continuous sputtering. Preliminary exhaust pressure 1×
After exhausting to ×10 ^-6 Torr, Ar gas was introduced to bring the temperature to 1 ×10 ^-3 Torr. *Base polyimide (thickness 20 μm) *Target Co-Cr alloy was used, and Nb and Ta were added in square Nb Required number of boards and Ta boards
The magnetic properties of the thin film were measured using a vibrating sample magnetometer (manufactured by Riken Electronics, hereinafter referred to as VSM).The composition of the thin film was determined by dispersion of energy. The crystal orientation was measured using a type microanalyzer (manufactured by KEVEX, hereinafter referred to as EDX) and an X-ray diffractometer (manufactured by Rigaku Denki).

Adding Nb as a third element to Co-Cr (2 to 10at
Figure 1 shows the in-plane hysteresis curve when a magnetic field of 15 KOe is applied to a recording medium sputtered with a film thickness of 0.2 μm on a polyimide base. The figure shows that the hysteresis curve rises abruptly and irregularly in the area where the magnetic field in the in-plane direction is near zero (arrow A in the figure).
), it can be seen that a so-called magnetization jump occurs. Sputtered Co−Cr−Nb
If we assume that the thin film always undergoes uniform crystal growth during sputtering, the magnetization jump shown in Figure 1 should not occur;
It is inferred that multiple crystal layers with different magnetic properties exist within the −Nb thin film.

Next, under the same experimental conditions as shown in Figure 1.
FIG. 2 shows the hysteresis curve in the in-plane direction when a magnetic field of 15 KOe is applied to a recording medium made of Co-Cr-Nb sputtered to a thickness of 0.05 μm on a polyimide base. In the same figure, there is no magnetization jump in the hysteresis curve as seen in Figure 1, and it is understood that the Co-Cr-Nb thin film with a film thickness of about 0.05 μm is a substantially uniform crystal. . In addition, when looking at the coercive force Hc at a film thickness of about 0.05 μm from the same figure, it is understood that the coercive force Hc has an extremely small value and the magnetic permeability in the in-plane direction is large. From the above results, the initial value of the coercive force Hc that first grows in the vicinity of the base by sputtering is small, and this initial layer is confirmed by scanning electron micrographs (see the above document). It is thought to be a crystalline layer of diameter. Furthermore, the layer that grows above the initial layer has a coercive force Hc that is larger than the coercive force Hc of the initial layer, and this layer is also a large-grain crystal layer confirmed by scanning electron micrographs. Conceivable.

Co− where small grain size crystal layer and large grain size crystal layer coexist
The reason why a magnetization jump occurs in a Cr--Nb thin film will be described below using FIGS. 3 to 5. As will be described later, magnetization jumps do not occur in all Co--Cr--Nb thin films due to the composition ratio and sputtering conditions. When a Co--Cr--Nb thin film is formed by sputtering under predetermined conditions and the hysteresis curve of this thin film is drawn by measurement, a hysteresis curve in which a magnetization jump appears as shown in FIG. 3 is obtained. In addition, a hysteresis curve consisting only of a small-grain crystal layer can be obtained by performing sputtering with a small film thickness (approximately 0.075 μm or less, which will be explained later) and measuring it (see Figure 4). show). Furthermore, the large-grain crystal layer is considered to have a uniform crystal structure, and the hysteresis curve shown in Figure 3 is a composite of the hysteresis curve of the small-grain crystal layer and the hysteresis curve of the large-grain crystal layer. Therefore, as shown in FIG. 5, the coercive force Hc is larger than that of the small-grain crystal layer, and it is thought that a smooth hysteresis curve with no magnetization jump is formed. In other words, the existence of the magnetization jump shown in FIG. 3 indicates that two layers with different magnetic properties are formed within the same thin film, and therefore the Co
It can be seen that the -Cr-Nb thin film also has two layers with different magnetic properties. The coercive force of a large-grain crystal layer can be calculated from the hysteresis curve of a Co-Cr-Nb thin film with a small-grain crystal layer and a large-grain crystal layer coexisting. It can be determined from the hysteresis curve obtained by subtracting the curves. Based on the above experimental results, Co
This proves that when a magnetization jump occurs in the hysteresis curve of the -Cr-Nb thin film, two layers with different magnetic properties are formed.

Next, the magnetic properties of each of the above two layers formed during sputtering on the base of the Co-Cr-Nb thin film will be explained below using Fig. 6 in relation to the thickness dimension of the Co-Cr-Nb thin film. explain. Figure 6 shows Co-
The film thickness of the Cr-Nb thin film is controlled by changing the sputtering time, and the in-plane coercive force Hc, the vertical coercive force Hc⊥,
The magnetization jump amounts σj are respectively depicted.

First, focusing on the coercive force Hc in the in-plane direction, it is an extremely small value (150 Oe or less) when the film thickness is 0.08 μm or less, and it is considered that the magnetic permeability in the in-plane direction is high. In addition, when comparing the values of the coercive force Hc⊥ in the vertical direction and the coercive force Hc in the in-plane direction, both of them are less than 150 Oe, and the difference is small, making the layer so-called isotropic. . Furthermore, even if the film thickness increases, the coercive force Hc does not change significantly. Also, when paying attention to the magnetization jump amount σj, the magnetization jump amount rises rapidly when the film thickness dimension is 0.075 μm and draws a smooth downward convex parabolic shape for film thicknesses of 0.075 μm or more. Furthermore, if we pay attention to the vertical coercive force Hc⊥,
The coercive force Hc⊥ rises rapidly at a film thickness of 0.05 μm to 0.1 μm, and exhibits a high coercive force of 900 Oe or more at a film thickness of 0.1 μm or more. These results show that the boundary between the small-grain crystal layer and the large-grain crystal layer is at a film thickness of approximately 0.075 μm, and that the small-grain crystal layer with a film thickness of 0.075 μm or less exists in the in-plane direction and vertical direction. coercive force against
It is a so-called low coercive force layer with low Hc and Hc⊥, and a large grain crystal layer with a film thickness of 0.075 μm or more has a low coercive force Hc in the in-plane direction, but a low coercive force Hc⊥ in the perpendicular direction. It is a so-called high coercive force layer having a very high value, and is suitable for perpendicular magnetic recording. Furthermore, in the film thickness dimension (0.075 μm or less) where no magnetization jump occurs,
Coercive force Hc, Hc in in-plane direction and perpendicular direction
⊥ is low, and when the film thickness is larger than this (0.075 μm or more), the coercive force Hc⊥ in the vertical direction increases rapidly. If a magnetization jump still occurs due to this, it is presumed that two layers with different magnetic properties are formed in the Co--Cr--Nb thin film.

Next, Ta is added as a third element to Co-Cr (1~
The same phenomenon occurs in the 10at% addition range),
FIG. 7 shows the results of the same experiment as in the case of adding Nb described above. Figure 7 shows Co-Cr-Ta
The film thickness of the thin film is controlled by changing the sputtering time, and the in-plane coercive force Hc, perpendicular coercive force Hc⊥, and magnetization jump amount σj are plotted for each film thickness. From the same figure, Co
When Ta is added to -Cr, almost the same results as when Nb is added to Co-Cr are obtained, and the boundary between the small-grain crystal layer and the large-grain crystal layer is approximately 0.075 μm thick. However, the small-grain crystal layer with a film thickness of 0.075 μm or less has a coercive force in the in-plane direction and the perpendicular direction.
It is a so-called low coercive force layer with low Hc and Hc⊥ (both Hc and Hc⊥ below 170 Oe). In addition to this, the vertical and in-plane coercive forces Hc⊥, Hc
The difference in the values of is small and the layer is so-called isotropic. In addition, although the large-grain crystal layer with a film thickness of 0.075 μm or more has a low coercive force Hc in the in-plane direction, the coercive force Hc⊥ in the perpendicular direction has a very high value (750 Oe or more).

What should be noted in the above experiment is that if the sputtering conditions and the added amounts of Nb and Ta are changed from the above values (Nb: 2 to 10 at%, Ta: 1 to 10 at%), no magnetization jump occurs; Co-Cr-Nb thin film, Co-Cr without magnetization jump
-A small grain size crystal layer and a large grain size crystal layer are formed also in the Ta thin film and the Co-Cr thin film (see the above-mentioned document). Co− that does not cause magnetization jump
An example of the hysteresis curve of a Cr-Nb thin film is shown in FIG. Figure 8A is an in-plane hysteresis curve including a small-grain crystal layer and a large-grain crystal layer, Figure 8B is an in-plane hysteresis curve of only a small-grain crystal layer, and Figure 8C is the in-plane hysteresis curve of only the large-grain crystal layer. From each figure, the residual magnetization Mr _B in the in-plane direction of the small-grain crystal layer is larger than the residual magnetization Mr _C of the large-grain crystal layer, so the residual magnetization Mr _A including both crystal layers is larger than that of the large-grain crystal layer. residual magnetization of
It is more disadvantageous than when only Mr _C is used, and the anisotropic magnetic field Hk
becomes smaller. Furthermore, it is known that the small-grain crystal layer has poor orientation (large Δθ50), and has a large coercive force Hc in the in-plane direction, making it unsuitable for perpendicular magnetic recording.

As mentioned above, when considering a Co-Cr-Nb thin film and a Co-Cr-Ta thin film having a small-grain crystal layer and a large-grain crystal layer as a perpendicular magnetic recording medium, the Co-Cr
- When attempting to create perpendicular magnetization in a Nb thin film or a Co-Cr-Ta thin film over the entire film thickness in a direction perpendicular to the film surface, the existence of a small-grain crystal layer is extremely disadvantageous for perpendicular magnetization. It was conventionally thought that this would be a factor (it would be a disadvantageous factor in the case where a magnetization jump occurs and in the case where a magnetization jump does not occur). In other words, in a small-grain crystal layer where a magnetization jump occurs, the coercive forces Hc and Hc⊥ in the in-plane and perpendicular directions are both extremely low (170 Oe or less), and it is thought that there is almost no perpendicular magnetization in this layer. . Furthermore, even in a small-grain crystal layer when no magnetization jump occurs, the in-plane coercive force Hc is larger than the coercive force Hc when a magnetization jump occurs, but the perpendicular coercive force Hc⊥ is There is no coercive force sufficient to realize perpendicular magnetic recording, and it is thought that good perpendicular magnetization cannot be achieved. Therefore, even if magnetization is performed in a direction perpendicular to the film surface, perpendicular magnetization in the small-grain crystal layer is hardly achieved, and the perpendicular magnetization efficiency of the magnetic film as a whole decreases. This effect is remarkable in a magnetic head such as a ring core head that contains a large amount of in-plane magnetic flux component.

However, the magnetic properties of the small-grain crystal layer in the present invention are that the coercive force Hc in the in-plane direction is small, and it has relatively high magnetic permeability and magnetic isotropy, which is different from that of the conventional Co-Cr thin film. It has similar characteristics to the backing layer disposed between the base and the base. In other words, Co
-In Cr-Nb thin film and Co-Cr-Ta thin film,
It is considered possible to use a small-grain crystal layer having a low coercive force Hc as a high magnetic permeability layer, which is a so-called underlayer.

Therefore, when a single film of Co-Cr-Nb thin film or Co-Cr-Ta thin film is sputtered, the small-grain crystal layer formed will function as a backing layer, and the large-grain crystal layer will function as a perpendicular magnetization layer. It is possible to make it work. However, Co-Cr-Nb thin film and Co-
In a single Cr-Ta thin film, the addition of Co-Cr
The amounts of Nb and Ta added are limited to a predetermined amount at which a magnetization jump occurs. Also, the ferromagnetic material Co
By adding Nb and Ta, which are nonmagnetic materials, to the material, the saturation magnetization Ms decreases, making it impossible to perform high-output perpendicular magnetic recording.

In view of this, in the present invention, under the conditions where the magnetization jump occurs, a small crystal layer of Co-Cr-Nb thin film or Co-Cr-Ta thin film is formed on the base (approximately 0.1 μm or less). Co-Cr-Nb thin film or Co in which the saturation magnetization Ms is increased by adding Nb and Ta in an amount smaller than the condition value that causes a magnetization jump.
-By sputtering a Cr-Ta thin film, we formed a large-grain crystal layer that directly contributes to perpendicular magnetic recording. Various magnetic properties when a Co-Cr-Nb thin film is used as a small-grain crystal layer in a perpendicular magnetic recording medium with the above configuration are compared with a Co-Cr-Nb single-layer thin film with a small addition amount of Nb and the occurrence of a magnetization jump. Figure 9 shows the recording wavelength and reproduction output of each thin film when magnetic recording and reproduction are performed on this perpendicular magnetic recording medium using a ring core head made of Sendust (registered trademark). The relationship is shown in Figure 10, and various magnetic properties when a Co-Cr-Ta thin film is used as a small-grain crystal layer are shown in Figure 10. Co−Cr−Ta
A comparison with a single-layer thin film is shown in FIG. 9 and 11, Co-Cr-Nb and Co-Cr-Ta (hereinafter Co
−Cr−Nb and Co−Cr−Ta are collectively referred to as Co−Cr
−Nb(Ta)) on a small-grain crystal layer of Nb or Ta that is smaller than the condition value that causes a magnetization jump.
A perpendicular magnetic recording medium (hereinafter referred to as a dual-layer medium) in which a large-grain crystal layer of Co-Cr-Nb (Ta) doped with Co-Cr-Nb (Ta) has a magnetization jump.
(Ta) The saturation magnetization Ms is larger than each single-layer perpendicular magnetic recording medium of thin film, and the perpendicular coercive force Hc⊥ is also a sufficiently high value, so it has characteristics suitable for perpendicular magnetization. ing. On the other hand, as shown in FIG. 10, the reproduction output and recording wavelength characteristics are different for the Co-Cr-Nb thin film perpendicular magnetic recording medium (hereinafter referred to as magnetization jump single layer medium) in which magnetization jump occurs.
Co-Cr-Nb thin film perpendicular magnetic recording medium with a small amount of added Nb (hereinafter abbreviated as low-addition single layer medium)
Compared to , the dual-layer medium shows high values in all recording wavelength regions and can obtain strong reproduction output.

Particularly in the short wavelength region (recording wavelength region of 1 μm to 0.2 μm), although magnetization jump single-layer media and low-doping single-layer media increase their reproduction output, dual-layer media can increase reproduction output with even higher efficiency. It is increasing. Therefore, it can be said that the dual-layer medium is particularly suitable for perpendicular magnetic recording and reproduction in the short wavelength region. Furthermore, Co-
Similar results were obtained with the Cr--Ta two-layer medium as shown in FIG.

The reason why the above phenomenon occurs will be deduced below using FIG. 12. Co-Cr-Nb is applied to the base 1 made of polyimide etc. by satisfying the conditions for generating a magnetization jump.
When (Ta) magnetic material is sputtered to a film thickness of approximately 0.1 μm, a Co-Cr-Nb film is formed as described above.
(Ta) The thin film has a small-grain crystal layer 2 in almost its entirety.
is thought to be formed. This small-grain crystal layer 2 is an isotropic layer with a small coercive force Hc in the in-plane direction and a small difference from the coercive force Hc⊥ in the perpendicular direction. Therefore, the small grain size crystal layer 2 can perform substantially the same function as a so-called backing layer.

In the upper part of the small-grain crystal layer 2, the amount of Nb and Ta added was set to be smaller than the condition value that causes a magnetization jump.
Co-Cr-Nb (Ta) magnetic material is sputtered to a film thickness of approximately 0.1 μm. From small grain crystal layer 2
Co-Cr-Nb(Ta) with small amounts of Nb and Ta added
When the magnetic material is sputtered onto the small-grain crystal layer 2, the boundary between the two magnetic materials is
Co-Cr-Nb(Ta) with small amounts of Nb and Ta added
A small-grain crystal layer of magnetic material hardly occurs (even if it occurs, it is thought that it will not reach a thickness that affects perpendicular magnetic recording characteristics), and a high saturation magnetization Ms
It is thought that the large-grain crystal layer 3, which has a strong coercive force in the perpendicular direction and directly contributes to perpendicular magnetization, grows immediately. In addition, in the Co-Cr-Nb (Ta) thin film forming the large-grain crystal layer 3, Nb and
The amount of Ta added can be arbitrarily selected without being restricted by the condition value that causes a magnetization jump as in the case of the small-grain crystal layer 2. As mentioned above, although the addition of Nb and Ta reduces the saturation magnetization Ms of Co,
The easy axis of magnetization of is strongly oriented in the vertical direction. accordingly
By appropriately selecting the amount of Nb and Ta added,
High saturation magnetization Ms can be maintained while the easy axis of magnetization of Co is strongly oriented in the perpendicular direction. The amounts of Nb and Ta added to the Co--Cr--Nb (Ta) thin film formed on the small-grain crystal layer 2 are selected to be the above-mentioned appropriate amounts. Therefore, the magnetic flux lines emitted from the ring core-shaped magnetic head 5 in sliding contact with the two-layer medium 4 penetrate the large-grain crystal layer 3 and reach the small-grain crystal layer 2, resulting in a low coercive force and an isotropic structure. It is thought that the magnetic flux advances in the in-plane direction within the small-grain crystal layer 2, which has a magnetic field, and that the magnetic flux is suddenly absorbed by the magnetic pole portion of the magnetic head 5, causing perpendicular magnetization in the large-grain crystal layer 3. . Therefore, the magnetic loop formed by the magnetic flux becomes a horseshoe shape as shown by the arrow in FIG. 12, and the magnetic flux concentrates and sharply penetrates the large-grain crystal layer 3 having a high saturation magnetization Ms at a predetermined perpendicular magnetic recording position. Large grain crystal layer 3
Perpendicular magnetization with large residual magnetization occurs. In addition, it is known that the thermal expansion coefficient of a recording medium can be adjusted by adding Nb and Ta, and it is therefore possible to adjust the thermal expansion coefficient by appropriately selecting the amounts of Nb and Ta added. can be adjusted,
A recording medium with less curl can be easily manufactured. In addition, the coercive force in the in-plane direction of the small-grain crystal layer 2
As shown in Figures 6 and 7, Hc is approximately 10 Oe to 50 Oe, which is not an extremely small value with respect to the coercive force Hc⊥ of the large-grain crystal layer 3, so it is good without causing impact Barkhausen noise. perpendicular magnetic recording and reproduction can be performed.

Effects of the Invention As described above, according to the perpendicular magnetic recording medium according to the present invention, a magnetic material made of cobalt and chromium with at least one of niobium and tantalum added to the base has a low coercive force and an abrupt magnetic field near the origin. Forming a layer having a magnetization jump, which is an in-plane M-H hysteresis characteristic represented by a rising curve, and producing the magnetization jump on the layer in an amount smaller than the amount of niobium or tantalum added to the layer. By forming a perpendicular magnetization layer made of a magnetic material in which at least one of cobalt and chromium is added to cobalt and chromium in an amount of at least one of niobium and tantalum, the perpendicular magnetic recording medium has a small coercive force in the in-plane direction on the base and a high magnetization. The structure consists of two layers: a layer with a jump, and a perpendicular magnetic layer that has high saturation magnetization, does not produce a magnetization jump, and has a large coercive force in the perpendicular direction. The magnetic flux easily enters a layer with a low coercive force and a magnetization jump, propagates in the horizontal direction, and then passes through a perpendicular magnetic layer with a high saturation magnetization and a high coercive force at the magnetic pole of the magnetic head to reach the magnetic head. Because the perpendicular magnetization layer is suddenly and sharply attracted to the magnetic pole of Magnetization is performed and good reproduction output can be obtained, and the layer having a magnetization jump functions reliably as a backing layer, and its coercive force is not unnecessarily small compared to the coercive force of the perpendicularly magnetized layer. Good perpendicular magnetic recording and reproduction can be performed without generating impulsive Barkhausen noise, and furthermore, the perpendicular magnetic layer formed on the layer having a magnetization jump can be used.
The amount of Nb and Ta added can be arbitrarily selected, and by selecting an appropriate amount that can maintain high saturation magnetization while strongly orienting the axis of easy magnetization of Co in the perpendicular direction, the playback output can be improved. It has the advantage of being able to realize very good perpendicular magnetic recording and reproduction, and because the coefficient of thermal expansion can be adjusted, a perpendicular magnetic recording medium with little curl can be easily manufactured.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a hysteresis curve of a Co-Cr-Nb thin film, which is a magnetic film of an embodiment of a perpendicular magnetic recording medium according to the present invention, and FIG. 2 is a diagram showing a hysteresis curve of a small-grain crystal layer. Figures 3 to 5 are diagrams for explaining the reasons why magnetization jumps occur, and Figure 6
The figure shows the two-layer structure of the Co-Cr-Nb thin film and the magnetic properties of each layer. Figure 7 shows the Co-Cr-Nb thin film.
Figure 8 shows the two-layer structure of the Cr-Ta thin film and the magnetic properties of each layer. Figure 8 shows an example of the hysteresis curve of a Co-Cr-Nb thin film with no magnetization jump. Figure 9. as a small-grain crystal layer
Various magnetic properties when using Co-Cr-Nb thin film
Figure 10 shows a comparison between a Co-Co-Cr-Nb single-layer thin film with a small amount of added Nb and a Co-Cr-Nb single-layer thin film with a magnetization jump. A diagram showing the relationship between recording wavelength and reproduction output of each thin film, Figure 11 shows Co-Cr-Ta as a small grain crystal layer.
Figure 1 shows various magnetic recording properties when using thin films in comparison with a Co-Cr-Ta single-layer thin film with a small amount of Ta added and a Co-Cr-Ta single-layer thin film with a magnetization jump. FIG. 12 schematically shows the crystal growth state of the recording medium of the present invention and shows the magnetic loop formed by the magnetic flux, and FIG. 13 shows the relationship between the recording wavelength and reproduction output of each thin film shown in FIG. 11. It is. DESCRIPTION OF SYMBOLS 1...Base, 2...Small grain size crystal layer, 3...Large grain size crystal layer, 4...Two layer medium, 5...Magnetic head.

Claims (1)

[Claims] 1 Magnetization jump, which is an in-plane M-H hysteresis characteristic expressed by a curve that rapidly rises near the origin, has a low coercive force on a base using a magnetic material made by adding at least one of niobium and tantalum to cobalt and chromium. and at the same time, on the layer, at least one of niobium and tantalum is added to cobalt and chromium in an amount smaller than the amount of niobium or tantalum added in the layer and in an amount that does not cause the magnetization jump. A perpendicular magnetic recording medium characterized by forming a perpendicular magnetic layer made of a magnetic material.