JPH0642282B2 - Perpendicular magnetic recording / reproducing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a perpendicular magnetic recording / reproducing method, and more particularly to a perpendicular magnetic recording / reproducing method capable of increasing a recording / reproducing output.

2. Description of the Related Art Generally, in order to record / reproduce on / from a magnetic recording medium by using a magnetic head, the magnetic layer of the magnetic recording medium is magnetized in the longitudinal direction (in-plane direction) of the magnetic recording medium and recorded. The thing to reproduce is general-purpose. However,
According to this, it is known that the higher the recording density, the larger the demagnetizing field and the demagnetizing effect adversely affects the high density recording. Therefore, in recent years, a perpendicular magnetic recording / reproducing method has been proposed which eliminates the above-mentioned adverse effects by magnetizing the magnetic layer of the magnetic recording medium in the perpendicular direction. According to this, as the recording density is improved, the demagnetizing field becomes smaller, and theoretically good high density recording in which the residual magnetization does not decrease can be performed.

Conventionally, in this perpendicular magnetic recording / reproducing method, a magnetic head composed of a main magnetic pole and an auxiliary magnetic pole is provided with a perpendicular magnetic recording medium interposed therebetween,
A strong perpendicular magnetic field is generated in the vicinity of the tip of the main magnetic pole, so that the perpendicular magnetic recording medium is perpendicularly magnetized.
As a perpendicular magnetic recording medium, C is formed on the base film.
In some cases, an o-Cr film was formed by sputtering. As is well known, the Co-Cr film has a relatively high saturation magnetization (Ms) and has an easy axis of magnetization perpendicular to the film surface (that is, the coercive force Hc⊥ in the direction perpendicular to the film surface is large. Therefore, it is known that it is an extremely promising material for a perpendicular magnetic recording medium. However, although the Co-Cr film has an easy axis of magnetization whose orientation (the C axis of the close-packed hexagonal crystal) is close to perpendicular due to the addition of Cr, it must be sufficiently oriented in the perpendicular direction. It was impossible to obtain a strong perpendicular magnetic anisotropy. Therefore, conventionally, Co-
There is a perpendicular magnetic recording medium having a structure in which the easy axis of magnetization of Co is strongly oriented in the perpendicular direction by adding a third element such as niobium (Nb) and tantalum (Ta) to Cr. In addition, a high permeability layer (that is, a layer having a small coercive force Hc, for example, Ni—Fe) which is a so-called backing layer is separately formed between the Co—Cr film and the base film to form a two-layer structure. There is a perpendicular magnetic recording medium having a structure in which the magnetic flux expanding therein is concentrated and sucked toward a magnetic pole of a magnetic head at a predetermined magnetic recording position to have a sharp distribution and strong perpendicular magnetization.

Problems to be Solved by the Invention In the above-described conventional perpendicular magnetic recording / reproducing method, in order to strongly orient the easy magnetization axis of Co of the perpendicular magnetic recording medium in the perpendicular direction, Co, Cr, Nb, Ta and the like are added. It was However, although the easy axis of magnetization of Co is strongly oriented in the perpendicular direction by the addition of Cr, Nb, and Ta, it is a ferromagnetic material of Co.
However, the addition of non-magnetic materials such as Cr, Nb, and Ta reduces the saturation magnetization Ms of the perpendicular magnetic recording medium, which makes it impossible to obtain a high reproduction output. When a ring core head is used as the magnetic head, the generated magnetic field contains a large amount of in-plane components, so that the efficiency is improved in the perpendicular magnetic recording medium having only strong anisotropy only in the vertical direction as described above. There is a problem that perpendicular magnetic recording cannot be performed well. Further, in the case of a double-layered perpendicular magnetic recording medium formed by using a high-permeability layer as a backing layer in addition to the Co-Cr film, the resistance of the high-permeability layer against 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 that shockable Barkhausen noise was generated. In addition to this, it is necessary to have a coercive force of at least 10 Oe or more to prevent this Barkhausen noise, but there is also a problem that there is no suitable material that satisfies this condition and has a function as a backing layer. Atsuta

Therefore, in the present invention, attention is paid to the fact that when a magnetic material formed by adding at least one of niobium and tantalum to cobalt and chromium is coated, the magnetic layer is divided into two layers having different coercive forces. It is an object of the present invention to provide a perpendicular magnetic recording / reproducing method which solves the above problems by positively utilizing the lower layer having a lower coercive force in perpendicular magnetic recording and performing perpendicular magnetic recording / reproduction by a ring core head.

Means for Solving the Problems In order to solve the above-mentioned problems, in the present invention, the magnetic force obtained by adding at least one of niobium and tantalum to cobalt and chromium causes resistance magnetic force on the base in the vicinity of the origin. A layer having a magnetization jump having an in-plane MH hysteresis characteristic represented by a sharply rising curve is formed, and the magnetization jump is formed on the layer in an amount smaller than the amount of niobium or tantalum added to the layer. A ring core head was used to record / reproduce on / from a perpendicular magnetic recording medium formed by forming a perpendicular magnetization layer made of a magnetic material in which at least one of niobium and tantalum which does not occur is added to cobalt and chromium.

EXAMPLE A perpendicular magnetic recording medium (hereinafter simply referred to as a recording medium) used in a perpendicular magnetic recording / reproducing method according to the present invention is prepared by firstly depositing cobalt (Co), chromium (C) on a base polyimide substrate.
Sputtering is performed with a magnetic material obtained by adding at least one of niobium (Nb) and tantalum (Ta) to r) as a target, and subsequently niobium (Nb) is added to Co and Cr thereon.
And at least one of tantalum (Ta) is added to the magnetic material in a smaller amount than the above amount, and the magnetic material is sputtered as a target.

Conventionally, when a metal or the like (for example, Co-Cr alloy) is sputtered on a base, the thin film formed does not form the same crystal structure in the vertical direction on the film surface, but an extremely thin portion near the base. First, a small crystal grain first crystal layer was formed, and then a large crystal grain second crystal layer was formed on top of it, by various experiments (eg, scanning electron microscope photography). (Edward R. Wuori and Professor JHJudy: “INI
TIAL LAYER EFFECT IN CO-C
R FILMS ", IEEE Trans., VOL.MA
G-20, No.5, SEPTEMBER 1984, P774〜
P775 or William G. Haines: “VSMPROFIL
ING OF Co Cr FILMS: A NEW
ANALYTICAL TECHNIQUE "IEEE"
Trans. , VOL, MAG-20, No. 5, SEPT
EMBER 1984, P812-P814).

The present inventor pays attention to the above viewpoint, based on a Co—Cr alloy,
In addition, various kinds of metals were sputtered with the addition of the third element, and the physical properties of the small-sized crystal layer formed and the large-sized crystal layer formed on the upper part were measured. When Nb or Ta is added as the alloy, the coercive force of the small grain size crystal layer is much smaller than that of the large grain size crystal layer, and there is no extreme difference between the coercive force in the vertical direction and in the in-plane direction. I got caught. In the present invention, a small grain size crystal layer having the resistance magnetic force and a small difference in coercive force in the vertical direction and the in-plane direction is used as an isotropic layer, and the addition amount of Nb and the difference a is added to the small grain size crystal layer. Co-Cr-Nb which has a small high saturation magnetization Ms and has a strong easy axis and is oriented in the vertical direction.
It is characterized in that a thin film or a Co-Cr-Ta thin film is formed and is used as a perpendicular magnetization layer, and perpendicular magnetic recording / reproduction is performed using a ring core head.

The coercive forces of the small grain size crystal layer and the large grain size crystal layer of the magnetic material obtained by adding at least one of Co, Cr, Nb and Ta formed by the sputtering method performed by the present inventor were measured below. The experimental results will be described in detail. Co-Cr thin film,
When the Co-Cr-Nb thin film and the Co-Cr-Ta thin film were sputtered, the spattering conditions were set as follows (the sputtering conditions were set equal in each case where Nb or Ta was added).

* Sputter device RF magnetron sputter device * Sputtering method Continuous sputtering. Preliminary exhaust pressure was exhausted to 1 × 10 ^-6 Torr and then Ar gas was introduced to obtain 1 × 10 ^-3 Torr * Base polyimide (thickness 20 μm) * Target Co-Cr alloy is used, Nb and Ta are added Was performed by disposing square Nb plates and Ta plates on the required number of Co—Cr alloys.

* Distance between target substrates 110mm The magnetic properties of the thin film are based on a vibrating sample magnetometer (manufactured by Riken Denshi,
The composition of the thin film is an energy dispersive microanalyzer (KEVEX, hereinafter ED).
(Abbreviated as X) and the crystal orientation was measured by an X-ray diffractometer (manufactured by Rigaku Denki).

Addition of Nb as a third element to Co-Cr (2-10 at%
The same phenomenon occurs in the range of addition), and a hysteresis curve in the in-plane direction 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 is shown in FIG. From the figure, it can be seen that the hysteresis curve rises abruptly and irregularly (indicated by arrow A in the figure) near the zero magnetic field in the in-plane direction, and so-called magnetization jump occurs. Sputtered Co-Cr
If it is assumed that the -Nb thin film always undergoes uniform crystal growth during sputtering, the magnetization jump shown in FIG. 1 should not occur, which results in a plurality of Co-Cr-Nb thin films having different magnetic properties. It is assumed that a crystal layer exists.

Then, under the same experimental conditions as shown in FIG.
FIG. 2 shows a hysteresis curve in the in-plane direction when a magnetic field of 15 KOe was applied to a recording medium obtained by sputtering r-Nb on a polyimide base with a film thickness of 0.05 μm. In the figure, it is understood that the magnetization jump of the hysteresis curve as seen in FIG. 1 does not occur, and the Co-Cr-Nb thin film at a film thickness of about 0.05 μm is a substantially uniform crystal. . In addition to this, paying attention to the coercive force Hc at a film thickness of about 0.05 μm, it is understood that the coercive force Hc has a very small value and the magnetic permeability in the in-plane direction is large. From the above results, the coercive force Hc of the initial layer initially grown near the base by spattering is small, and this initial tank is confirmed by scanning electron micrographs (see the above sample). It is considered to be a crystal layer having a diameter. Further, the layer grown above the initial layer has a coercive force Hc larger than the coercive force Hc of the initial layer, and this layer is also a large grain crystal layer confirmed by a scanning electron microscope photograph. Conceivable.

Co-Cr-N in which a small grain size crystal layer and a large grain size crystal layer coexist
The reason why the magnetization jump occurs in the thin film b will be described below with reference to FIGS. 3 to 5. As will be described later, the magnetization jump does not occur in all Co—Cr—Nb thin films with respect to the composition ratio and the sputtering condition.
When a Co—Cr—Nb thin film is formed by sputtering under predetermined conditions and a hysteresis curve of this thin film is drawn by measurement, a hysteresis curve in which a magnetization jump appears appears as shown in FIG. Also, a hysteresis curve consisting of a small grain size crystal layer can be obtained by performing spattering with a small film thickness dimension (about 0.075 μm or less, which will be described later) and measuring it (see FIG. 4). Shown). The large crystal grain layer is considered to have a uniform crystal structure, and the hysteresis curve shown in FIG. 3 is a combination of the hysteresis curve of the small crystal grain layer and the hysteresis curve of the large crystal grain layer. It is considered that the coercive force Hc is larger than that of the small grain size crystal layer, as shown in FIG. 5, and forms a smooth hysteresis curve without magnetization jump. That is, the presence of the magnetization jump shown in FIG. 3 indicates that two layers having different magnetic properties are formed in the same thin film, and accordingly, the Co-- shown in FIG. It can be understood that the Cr-Nb thin film also has two layers having different magnetic properties. The coercive force of the large grain crystal layer is determined from the hysteresis curve of the Co—Cr—Nb thin film in which the small grain crystal layer and the large grain crystal layer coexist. It can be obtained from the hysteresis curve obtained by subtracting the curve. According to the above experimental results, when a magnetization jump occurs in the hysteresis curve of the Co-Cr-Nb thin film,
It was proved that two layers having different magnetic properties were formed.

Subsequently, the magnetic properties of each of the two layers formed during the sputtering of the Co-Cr-Nb thin film on the base are determined by Co
It will be described below with reference to FIG. 6 in relation to the thickness dimension of the —Cr—Nb thin film. In FIG. 6, the film thickness dimension of the Co—Cr—Nb thin film is controlled by changing the sputtering time, and the coercive force Hc in the in-plane direction, the coercive force Hc⊥ in the vertical direction, and the magnetization jump amount σj at each film thickness dimension are controlled. They are drawn respectively.

First, paying attention to the coercive force Hc in the in-plane direction,
Extremely small value under 0.08 μm (150 Oe or less)
Therefore, it is considered that the magnetic permeability in the in-plane direction is high. In addition to this, when comparing the values of the coercive force Hc⊥ in the vertical direction and the coercive force Hc in the in-plane direction, it was found that the values were 150 Oe or less in both directions, and the difference was small, forming a layer with so-called isotropic properties. . Further, the coercive force Hc does not change significantly even when the film thickness is large. Focusing on the amount of magnetization jump σj, the amount of magnetization jump is 0.075
It sharply rises at μm and draws a smooth downward convex parabola at a film thickness of 0.075 μm or more. Furthermore, focusing on the coercive force Hc⊥ in the vertical direction, the coercive force Hc⊥ is the film thickness dimension.
A sharp rise from 0.05 μm to 0.1 μm shows a high coercive force of 900 Oe or more at a film thickness of 0.1 μm or more. From these results, the boundary between the small grain size crystal layer and the large grain size crystal layer is approximately 0.075 μm.
The small grain size crystal layer having a thickness of 0.075 μm or less has a low coercive force Hc, Hc⊥ in the in-plane direction and the vertical direction, which is a so-called low coercive force layer. A large grain size crystal layer having a thickness of 0.075 μm or more has a low coercive force Hc in the in-plane direction, but has a very high coercive force Hc⊥ in the vertical direction. It is a layer suitable for recording.
Further, in the film thickness dimension (0.075 μm or less) where the magnetization jump does not occur, the coercive forces Hc and Hc⊥ in the in-plane direction and the perpendicular direction are low, and the film thickness dimension larger than this (0.07 μm)
5 μm or more), the coercive force Hc⊥ in the vertical direction
Will increase rapidly. Even if the magnetization jump occurs due to this, it is presumed that two layers having different magnetic properties are formed in the Co—Cr—Nb thin film.

Next, Ta is added to Co—Cr as a third element (1 to 10).
The same phenomenon occurs in the addition range of at%), and the result of performing the same experiment as in the case of adding Nb described above is
Shown in the figure. FIG. 7 shows that the film thickness dimension of the Co-Cr-Ta thin film is controlled by changing the sputtering time, and the coercive force Hc in the in-plane direction, the coercive force Hc⊥ in the vertical direction, and the magnetization jump amount σj at each film thickness dimension. They are drawn respectively. From the figure, when Ta is added to Co-Cr,
A result similar to the case of adding Nb to -Cr is obtained,
The boundary between the small grain crystal layer and the large grain crystal layer is at a film thickness dimension of about 0.075 μm, and the small grain crystal layer having a film thickness dimension of 0.075 μm or less has a coercive force Hc in the in-plane direction and the vertical direction.
, Hc⊥ is low (both Hc and Hc⊥ are 170 Oe or less),
It is a so-called low coercive force layer. In addition to this, the difference between the values of the coercive forces Hc⊥ and Hc in the vertical and in-plane directions is small, and the layer is so-called isotropic. In addition, the film thickness dimension
Coercive force Hc in the in-plane direction for large grain crystal layers of 0.075 μm or more
Although it is low, the coercive force Hc⊥ in the vertical direction is extremely high (750 Oe or more).

It should be noted that in the above experiment, the sputtering conditions and the amounts of Nb and Ta added are the above-mentioned values (Nb: 2 to 10).
At%, Ta: 1 to 10 at%), the magnetization jump does not occur, but the magnetization jump does not occur.
Cr-Nb thin film, Co-Cr-Ta thin film and Co-Cr
This means that a small grain size crystal layer and a large grain size crystal layer are also formed in the thin film (see the above-mentioned reference). An example of the hysteresis curve of the Co-Cr-Nb thin film in which the magnetization jump does not occur is shown in FIG. FIG. 8 (A) is an in-plane hysteresis curve including a small grain size crystal layer and a large grain size crystal layer,
FIG. 8 (B) is a hysteresis curve in the in-plane direction of only the small grain crystal layer, and FIG. 8 (C) is a hysteresis curve in the in-plane direction of the large grain crystal layer only. From each figure, the remanent magnetization Mr _B in the in-plane direction of the small grain crystal layer is the remanent magnetization M of the large grain crystal layer.
Since it is larger than r _{C, the} residual magnetization M including both crystal layers
r _A is more disadvantageous than when only the residual magnetization Mr _C of the large grain crystal layer is used, and the anisotropic magnetic field Hk becomes smaller. It is also known that the small grain size crystal layer has a poor orientation (large Δθ50), and the coercive force Hc in the in-plane direction is also large, which is not suitable for perpendicular magnetic recording.

When the Co--Cr--Nb thin film and the Co--Cr--Ta thin film having the small grain size crystal layer and the large grain size crystal layer as described above are considered as the perpendicular magnetic recording medium, the Co--Cr--Nb thin film and the Co--Cr--Nb thin film are used. When it is attempted to perform perpendicular magnetization on a Cr-Ta thin film in the direction perpendicular to the film surface over the entire film thickness, the existence of a small grain size crystal layer is conventionally considered to be an extremely disadvantageous factor for the perpendicular magnetization. (It becomes a disadvantageous factor in the case where the magnetization jump occurs and the case where the magnetization jump does not occur). That is, the coercive force Hc and Hc⊥ in the in-plane direction and the perpendicular direction are both extremely low (170 Oe or less) in the small grain crystal layer where the magnetization jump occurs, and it is considered that the perpendicular magnetization is hardly generated in this layer. . Also in the small grain size crystal layer in the case where the magnetization jump is not generated, the coercive force Hc in the in-plane direction is larger than the coercive force Hc in the case where the magnetization jump is generated, but the coercive force Hc⊥ in the vertical direction is It is considered that there is not enough coercive force to realize perpendicular magnetic recording, and good perpendicular magnetization cannot be achieved. Therefore, even if the magnetization is performed in the direction perpendicular to the film surface, the perpendicular magnetization in the small grain crystal layer is hardly performed, and the perpendicular magnetization efficiency of the entire magnetic film is reduced. This effect is remarkable in a magnetic head, such as a ring core head, which contains many in-plane components of magnetic flux.

However, the magnetic characteristics of the small grain size crystal layer in the present invention have a small coercive force Hc in the in-plane direction, a relatively high magnetic permeability and magnetic isotropy.
It has characteristics similar to the backing layer disposed between the Cr thin film and the base. That is, Co-Cr-Nb thin film and Co-Cr
In a -Ta thin film, it is considered possible to use a small grain size crystal layer having a low coercive force Hc as a so-called backing layer having a high magnetic permeability.

Therefore, the small grain crystal layer formed when the single film of the Co-Cr-Nb thin film and the Co-Cr-Ta thin film is sputtered functions as the backing layer, and the large grain crystal layer serves as the perpendicular magnetization layer. It is possible to make it function. However, in the single film of Co-Cr-Nb thin film and Co-Cr-Ta thin film, the addition amount of Nb and Ta added to Co-Cr is restricted to a predetermined amount at which the magnetization jump occurs. Further, the saturation magnetization Ms is lowered by adding Nb and Ta which are non-magnetic materials to Co which is a ferromagnetic material, so that high output perpendicular magnetic recording cannot be performed.

In view of this point, in the present invention, under the condition that the above-mentioned magnetization jump occurs, first, a Co-Cr-Nb thin film or Co is formed on the base.
Form a small grain size crystal layer of -Cr-Ta thin film (approx.
m or less), and a Co-Cr-Nb thin film or a Co-Cr-Ta thin film having a large saturation magnetization Ms with the added amount of Nb and Ta being smaller than the condition value that causes the magnetization jump, is sputtered for perpendicular magnetic recording. A large grain crystal layer that directly contributed was formed. In the perpendicular magnetic recording medium having the above-mentioned structure, various magnetic characteristics in the case of using a Co-Cr-Nb thin film as a small grain crystal layer are obtained by using Co-Cr-N with a small amount of Nb added.
b Single layer thin film and Co-Cr- with magnetic jump
Compared with the Nb single-layer thin film, FIG. 9 shows the recording wavelength and reproduction output of each thin film shown in FIG. 9 when perpendicular magnetic recording and reproduction were performed on this perpendicular magnetic recording medium with a ring core head made of Sendust (registered trademark). The relationship is shown in FIG. 10, and various magnetic characteristics when a Co—Cr—Nb thin film is used as a small grain size crystal layer are shown in FIG. 11 in comparison with the single layer thin film of Co-Cr-Ta described above, and recording of each thin film shown in FIG. 11 when perpendicular magnetic recording and reproduction were performed on this perpendicular magnetic recording medium with a ring core head made of sendust. FIG. 13 shows the relationship between the wavelength and the reproduction output. 9 and 11
As shown in the figure, Co-C formed under the condition that a magnetization jump occurs
r-Nb and Co-Cr-Ta (hereinafter Co-Cr-Nb
And Co-Cr-Ta are collectively referred to as Co-Cr-Nb
(Denoted as (Ta)) C in which an amount of Nb or Ta smaller than the condition value causing the magnetization jump is added on the small grain crystal layer (denoted by (Ta)).
A perpendicular magnetic recording medium (hereinafter referred to as a two-layer medium) on which a large grain crystal layer of o-Cr-Nb (Ta) is formed is a single layer of a Co-Cr-Nb (Ta) thin film having a magnetization jump. The saturation magnetization Ms is larger than that of the perpendicular magnetic recording medium, and the coercive force Hc⊥ in the perpendicular direction is also a high value, which is a characteristic suitable for perpendicular magnetization. On the other hand, as shown in FIG. 10, the reproduction output and the recording wavelength characteristics are such that the perpendicular magnetic recording medium of the Co—Cr—Nb thin film in which the magnetization jump occurs (hereinafter referred to as the magnetization jump single layer medium) and the addition amount of Nb are small. In comparison with the perpendicular magnetic recording medium of Co-Cr-Nb thin film (hereinafter abbreviated as a low-doped single layer medium), the double-layer medium shows a high value in all recording wavelength regions and a strong reproduction output can be obtained. .

Particularly short wavelength range (recording wavelength range from 1 μm to 0.2 μm)
In (1), the reproduction output is increased more efficiently in the double-layer medium, whereas the magnetization jump single-layer medium and the low-doped single-layer medium also increase the reproduction output. Therefore, it can be said that the double-layer medium is particularly suitable for perpendicular magnetic recording / reproduction in the short wavelength region. Similar results were obtained with a Co-Cr-Ta two-layer medium as shown in FIG.

The reason why the above phenomenon occurs will be inferred below with reference to FIG. Co-Cr-Nb (Ta) magnetic material is applied to the base 1 such as polyimide by satisfying the condition that a magnetic jump is generated.
When the sputtering is performed with the film thickness of 0.1 μm, it is considered that the Co-Cr-Nb (Ta) thin film coated as described above has the small grain crystal layer 2 formed almost entirely. This small grain crystal layer 2 has a coercive force Hc in the in-plane direction.
Is small and has a small difference from the coercive force Hc⊥ in the vertical direction and is an isotropic layer. Therefore, the small grain size crystal layer 2 can be made to perform a function substantially similar to that of a so-called backing layer.

On the upper part of the small grain crystal layer 2, Co-Cr-N is used in which the amount of Nb and Ta added is smaller than the condition value at which the magnetization jump occurs.
The b (Ta) magnetic material is sputtered with a film thickness of about 0.1 μm. When a Co—Cr—Nb (Ta) magnetic material having a smaller amount of Nb and Ta added than the small grain size crystal layer 2 is sputtered on the small grain size crystal layer 2, both have similar crystal structures and compositions. Because of the presence of Co, the amount of Nb and Ta added in the boundary portion of both magnetic materials is small.
-The small grain size crystal layer of the Nb (Ta) thin film material hardly occurs (even if it occurs, it is considered that it does not reach the thickness that affects the perpendicular magnetic recording characteristics), has a high saturation magnetization Ms, and has a perpendicular direction. It is considered that the large grain crystal layer 3 having a strong coercive force and directly contributing to the perpendicular magnetization grows immediately. Further, Co—Cr—Nb forming the large grain crystal layer 3
In the (Ta) thin film, the amounts of Nb and Ta added can be arbitrarily selected without being restricted by the condition value that causes the magnetization jump, as in the small grain crystal layer 2. As mentioned above, N
Although the saturation magnetization Ms of Co is lowered by the addition of b and Ta, the easy axis of magnetization of Co is strongly oriented in the vertical direction.
Therefore, by appropriately selecting the addition amounts of Nb and Ta, it is possible to maintain the high saturation magnetization Ms while strongly orienting the easy axis of Co in the perpendicular direction. Small grain crystal layer 2
The amount of Nb and Ta added to the Co-Cr-Nb (Ta) thin film formed above is selected to be the above appropriate amount. Therefore, the magnetic flux lines slidably contacting the two-layer medium 4 and emitted from the ring core head 5 pass through the large grain crystal layer 3 to reach the small grain crystal layer 2 and are small in resistance magnetic force and isotropic. It is considered that the magnetic flux advances in the in-plane direction in the grain size crystal layer 2 and is abruptly absorbed by the magnetic pole portion of the ring core head 5, whereby the large grain size crystal layer 3 is perpendicularly magnetized. Therefore, the magnetic loop formed by the magnetic flux has a horseshoe shape as shown by an arrow in FIG. 12 and has a high saturation magnetization Ms at a predetermined perpendicular magnetic recording position.
Since the magnetic flux is concentrated and sharply penetrates into the large-grain crystal layer 3 having, the large-grain crystal layer 3 is perpendicularly magnetized with a large residual magnetization. That is, even in the ring core head 5 that generates a magnetic field containing a large amount of in-plane components, it is possible to perform strong perpendicular magnetic recording with a large residual magnetization, and improve the magnetic recording / reproducing efficiency. In addition to this, N
It is known that the thermal expansion coefficient of the recording medium can be adjusted by adding b and Ta. Therefore, the thermal expansion coefficient can be adjusted by making it possible to appropriately select the addition amounts of Nb and Ta, A recording medium with less curl can be easily manufactured. Further, the coercive force Hc in the in-plane direction of the small grain crystal layer 2 is about 10 Oe to 50 Oe from FIGS. 6 and 7, which is extremely small with respect to the coercive force Hc⊥ of the large grain crystal layer 3. Since there is no impact Barkhausen noise, good perpendicular magnetic recording and reproduction can be performed.

As described above, according to the perpendicular magnetic recording / reproducing method of the present invention, the magnetic material formed by adding at least one of niobium and tantalum to cobalt and chromium causes the resistance magnetic force to rapidly increase on the base near the origin. Forming a layer having a magnetization jump which is an in-plane M-H hysteresis characteristic represented by a curve that rises at the same time, and causes the magnetization jump on the layer in an amount smaller than the amount of niobium or tantalum added to the layer. By using a ring core head for recording / reproducing on a perpendicular magnetic recording medium formed by forming a perpendicular magnetic layer made of a magnetic material in which at least one of niobium and tantalum in an amount not present is added to cobalt and chromium, The perpendicular magnetic recording medium has a lower layer having a small coercive force in the in-plane direction and isotropic on the base, and a high saturation magnetization and a perpendicular layer. Since the two layers, the upper layer and the upper layer, which have a large coercive force, are formed, the magnetic flux emitted from the ring core head easily enters the lower layer which has resistance magnetic force and isotropic property, and then travels in the horizontal direction. In a ring core head that has a strong remanent magnetization and generates a magnetic field containing a large amount of in-plane components because it is rapidly and sharply absorbed by the magnetic pole of the ring core head through the upper layer having high saturation magnetization and high coercive force. Perpendicular magnetic recording and reproduction that can realize a high reproduction output can be performed. In addition to this, excellent perpendicular magnetization can be performed especially for a short recording wavelength and a good reproduction output can be obtained, and the lower layer has a magnetization jump. Occurs,
That is, since the layer has a small coercive force in the in-plane direction and has an isotropic property, it reliably functions as a so-called backing layer and its coercive force is not a value unnecessarily small with respect to the coercive force of the upper layer, so that the impact Good perpendicular magnetic recording and reproduction can be performed without generating Barkhausen noise, and the addition amount of Nb and Ta in the upper layer can be arbitrarily selected. By properly selecting the amount that can maintain the high saturation magnetization while strongly orienting the axis in the vertical direction, good perpendicular magnetic recording / reproduction with a large reproduction output can be realized, and the coefficient of thermal expansion can be adjusted, so that the vertical direction with less curl It has the feature that a magnetic recording medium can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a magnetic film Co-C of one embodiment of a perpendicular magnetic recording medium used in the perpendicular magnetic recording / reproducing method according to the present invention.
FIG. 2 is a diagram showing a hysteresis curve of an r-Nb thin film, FIG. 2 is a diagram showing a hysteresis curve of a small grain crystal layer, and FIGS. 3 to 5 are diagrams for explaining the reason why magnetization jump occurs.
FIG. 6 is a diagram showing that the Co—Cr—Nb thin film has a two-layer structure and the magnetic characteristics of each layer, and FIG. 7 is Co—Cr.
-A diagram showing that the Nb thin film has a two-layer structure and the magnetic characteristics of each layer. Fig. 8 shows C in which no magnetization jump occurs.
FIG. 9 is a diagram showing an example of a hysteresis curve of an o-Cr-Nb thin film, and FIG. 9 shows various magnetic characteristics when a Co-Cr-Nb thin film is used as a small-grain-size crystal layer, Co- with a small amount of Nb added. The figure shown in comparison with the Cr-Nb single-layer thin film and the Co-Cr-Nb single-layer thin film in which the magnetization jump has occurred.
FIG. 11 shows the relationship between the recording wavelength and the reproduction output of each thin film shown in FIG. 9, and FIG. 11 shows Co-Cr- as a small grain crystal layer.
The figure which shows various magnetic recording characteristics when a Ta thin film is compared with a Co-Cr-Ta single-layer thin film with a small addition amount of Ta and a Co-Cr-Ta single-layer thin film in which a magnetization jump occurs. FIG. 12 is a diagram schematically showing a crystal growth state of a perpendicular magnetic recording medium used in the perpendicular magnetic recording / reproducing method according to the present invention and showing a magnetic loop formed by magnetic flux.
The figure is a diagram showing the relationship between the recording wavelength and the reproduction output of each thin film shown in FIG. 1 ... Base, 2 ... Small grain crystal layer, 3 ... Large grain crystal layer, 4 ... Double layer medium, 5 ... Ring core head.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichiro Imaoka 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan, Ltd.

Claims (2)

[Claims] 1. An in-plane MH hysteresis characteristic represented by a curve having a low coercive force and rapidly rising near the origin on a base by a magnetic material obtained by adding at least one of niobium and tantalum to cobalt and chromium. And forming a layer having a magnetization jump of at least one of niobium and tantalum in an amount less than the amount of niobium or tantalum added to the layer, cobalt and tantalum in an amount that does not cause the magnetization jump. A perpendicular magnetic recording / reproducing method characterized in that a signal is recorded / reproduced on / from a perpendicular magnetic recording medium having a perpendicular magnetic layer formed of a magnetic material added to chromium, using a ring core head. 2. The perpendicular magnetic recording / reproducing method according to claim 1, wherein the ring core head is made of Sendust (registered trademark).