JPS61224135A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a high reproducing output by forming the lower layer obtained by incorporating a specified amt. of other elements into cobalt and chromium on a base and forming the upper layer obtained by incorporating the smaller amt. of the same elements into cobalt and chromium on the lower layer to constitute the titled vertical magnetic recording medium having an in-plane M-H hysteresis characteristic shown by a curve having a steep rise in the vicinity of the origin. CONSTITUTION:The lower layer obtained by incorporating a specified amt. of other elements into cobalt and chromium is formed on a base and the upper layer obtained by incorporating the smaller amt. of the same elements into cobalt and chromium is formed on the lower layer. Consequently, the obtained vertical magnetic recording medium is provided with an in-plane M-H hysteresis characteristic shown by a curve having a steep rise in the vicinity of the origin. Accordingly, the magnetic flux emitted from a magnetic head is passed through the upper layer having high coercive force and absorbed rapidly and sharply by the magnetic pole of the magnetic head, strong residual magnetization is generated in the upper layer and hence a high reproducing output can be realized.

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.

Conventional technology Generally, recording is performed on a magnetic recording medium using a magnetic head.

In order to perform reproduction, a commonly used system is to magnetize the magnetic layer of a magnetic recording medium in the longitudinal direction (in-plane direction) of the medium using a magnetic head, record the information, and then reproduce the recorded information. However, according to this method, it is known that as the recording density increases, the demagnetizing field increases and the demagnetizing effect adversely affects 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 GO--Cr film is formed on a base film by sputtering. As is well known, c
The o-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), so it has perpendicular magnetization. It is known that it is an extremely promising material as a recording medium. However, the axis of easy magnetization of the co-Cr film is Cr.
Although the easy axis of magnetization of Co (C axis of R-dense 60,000 crystal) is oriented close to perpendicular, it is not fully oriented in the perpendicular direction and strong perpendicular magnetic anisotropy can be obtained. could not. For this reason, conventionally, niobium (Nb >
There is also a perpendicular magnetic recording medium in which the axis of easy magnetization of CO is strongly oriented in the perpendicular direction by adding a third element such as tantalum (Ta). In addition, between the co-crs and the base film, there is a high magnetic permeability layer (i.e., a layer with low coercive force Hc, such as Ni-F
e) is formed separately to have a two-layer structure^ The magnetic flux spreading within the magnetic permeability layer is concentrated and attracted to the magnetic pole of the magnetic head at a predetermined magnetic recording position, thereby creating a sharp perpendicular magnetization with a sharp distribution. There is a perpendicular magnetic recording medium with a configuration that allows this.

Problems to be Solved by the Invention In the above-mentioned conventional perpendicular magnetic recording medium, in order to strongly orient the axis of easy magnetization of CO in the perpendicular direction, Cr and Nb are added to CO.
, Ta, etc. were added. However, Or and Nb, T
Although the easy axis of magnetization of CO is strongly oriented in the perpendicular direction by the addition of a,
Also, by adding Nb and Ta, the saturation magnetization MS of the perpendicular magnetic recording medium decreases, making it impossible to obtain high reproduction output. G again
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 an o-Cr film, the coercive force of the high magnetic permeability layer is Since the coercive force 1-1c was extremely small (1000 or less), there was a problem in that an impulsive Barkhausen noise was generated.

In addition, in order to prevent this Barkhausen noise, it is necessary to have a coercive force of at least 100e, but there is also the problem that there is no suitable material that satisfies this condition and functions as a backing layer. there were.

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

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has a lower layer formed by containing cobalt, chromium, and other elements in predetermined amounts on a base, and a lower layer containing cobalt, chromium, and the above-mentioned other elements on this lower layer. The perpendicular magnetic recording medium has an in-plane M-H hysteresis characteristic represented by a curve with a sharp rise near the origin by forming an upper layer containing the same element as the element in an amount smaller than the predetermined amount. It was configured as follows.

Embodiment A perpendicular magnetic recording medium (hereinafter simply referred to as a recording medium) according to the present invention is manufactured by first depositing cobalt (CO), chromium (Cr), niobium (Nb), and tantalum (Ta) on a polyimide substrate. sputtering using a magnetic material as a target, followed by CO, Cr, niobium (Nb) and tantalum (Ta).
It can be obtained by sputtering using as a target a magnetic material to which at least one of them is added in a smaller amount than during the above addition.

Conventionally, when sputtering metal etc. (e.g. Go-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. It is becoming (
E dward R, Wuori and P
rofessor J.

H, Judy: ”INITIAL LAYERE
FFECT IN Co-CRFTLMS”.

IEEE Trans, , VOL, MAG-20°N
o, 5. SEPTEMBER1984, P 774~P
775 or William G. Haines:
“VSMPROF I LING OF Co.
CrFTLMS: A NEW ANALYTIC
ALTECHN rQLIE'' IEEE Tran
s, , VOL, MAG-20, No, 5. S.E.
PTEMBER1984, P 812-P 814
).

The Ministry of the Invention has focused on the above points and based on Co-Cr alloy,
In addition, as a result of sputtering various metals to which a third element was added, and measuring the physical properties of the small crystal layer formed and the large crystal layer formed on top of it, we found that the third element When Nb or Ta is added, the coercive force of the small-grain crystal layer is much smaller than that of the large-grain crystal layer, and there is no extreme difference between the coercive force in the vertical direction and the in-plane direction. I understand. 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 on this small-grain crystal layer, the amount of Nb and Ta added is CO-Cr-N has a low and high saturation magnetization MS, and the easy axis of magnetization is strongly oriented in the perpendicular direction.
It is characterized in that a b tlli, t taha, C0-Cr-Ta WJ film is formed and this is used as a perpendicular magnetization layer.

The following experiment was conducted by the present inventor to measure the coercive force of a small-grain crystal layer and a large-grain crystal layer of a magnetic material formed by sputtering and containing at least one of Go, Cr, Nb, and Ta. Detail the results. Go-Cr
fil film, co -Cr-Nb thin film and CO-Cr
When sputtering the -Tam film, the sputtering conditions were set as shown in F (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×x 10-6
After exhausting to Torr, Ar gas was introduced and 1
*Base polyimide (thickness 20 μm) with Q-3T Orr *Target Go-Cr gold alloy is used, and Nb and Ta are added by placing the required number of square Nb plates and Ta plates on the co-Cr alloy. The magnetic properties of the ugly thin film were measured using a vibrating sample magnetometer (manufactured by I!Iken Electronics, hereinafter referred to as VSM), and the composition of the thin film was measured using an energy dispersive microanalyzer (KEVEX). The crystal orientation was measured using an X-ray diffractometer (manufactured by Rigakuden).

Adding Nb as a third element to Go-Cr (2 to 1 Qat
% addition range), and FIG. 1 shows a hysteresis curve in the in-plane direction when a magnetic field of 15 KOe is applied to a recording medium sputtered to a film thickness of 0.2 μm on a polyimide base. It can be seen from the figure that the hysteresis curve rises abruptly and irregularly (indicated by arrow A in the figure) at a portion where the in-plane magnetic field is near zero, and a so-called magnetization jump occurs. Sputtered C0
If we assume that the -Cr-Nb I film always undergoes uniform crystal growth during sputtering, the magnetization jump shown in Figure 1 should not occur, and from this we can conclude that the Go -C
It is presumed that a plurality of crystal layers having different magnetic properties exist within the r-Nb thin film.

Next, under the same experimental conditions as shown in Fig. 1, Go −
FIG. 2 shows a hysteresis curve in the in-plane direction when a magnetic field of 15 KOe is applied to a recording medium in which Cr--Nb is sputtered to a film thickness of 0.05 μm on a polyimide base. In the figure, there is no magnetization jump in the hysteresis curve as seen in Figure 1, and it can be seen that the Co-Cr-Nb thin film with a film thickness of about 0.05 μm has an approximately uniform crystal structure. be done. In addition to this, from the same figure 0
．． When 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 an extremely small value and the magnetic permeability in the in-plane direction is large. From the above results, the initial layer that first grows in the vicinity of the base by sputtering has a small coercive force HC/, and this initial layer grows in the vicinity of the base, as confirmed by scanning electron micrographs (see the above document). This is thought to be a crystal layer with small grain size. In addition, the layer growing above the initial layer has a coercive force HC/ larger than that of the initial layer, and this layer is also a large-grain crystal layer confirmed by scanning electron micrographs. It is believed that there is.

Co -Cr- 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 Nb thin film will be described below using FIGS. 3 to 5. As will be described later, the magnetization jump does not occur in all Go--Cr--Nb thin films, depending on the composition ratio and sputtering conditions. Under certain conditions, Co -Cr -Nb
When 811 is formed by sputtering 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 0.075μ or less, which will be described later) and measuring it (see Section 4). (shown in figure).

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 in the same thin film, and therefore the Co-Cr-Nb shown in FIG. It can be seen that two layers with different magnetic properties are formed in the N film as well.

The coercive force of the large-grain crystal layer can be calculated from the hysteresis curve of the Go-Cr-Nb thin film with both the small-grain crystal layer and the large-grain crystal layer. It can be determined from the hysteresis curve obtained by subtracting the curves.

Based on the above experimental results, Co -Cr -Nb wJll
When a magnetization jump occurs in the hysteresis curve, it is proven that two layers with different magnetic properties are formed.

Subsequently, the magnetic properties of each of the two layers formed during sputtering onto the base of the Go-Cr-Nb thin film are determined by
The following description will be made with reference to FIG. 6 in relation to the thickness dimension of the o-Cr-Nb thin film. Fig. 6 Go -Cr -Nb
The film thickness of 3i1111 is controlled by changing the sputtering time, and a magnetization jump amount σj is grooved on the in-plane coercive force HC/ and the perpendicular coercive force Hc at each film thickness.

First of all, paying attention to the coercive force HC/ in the in-plane direction, it is extremely small (1500 μm or less) when the film thickness is 0.08 μm or less.
8 or less), and the magnetic permeability in the in-plane direction is considered to be high. In addition, when comparing the values of the vertical coercive force 1-1c and the in-plane coercive force HC/, both partners are 1-1c.
It is 50Qe or more F, and the difference is small, making it a so-called isotropic layer. Furthermore, even if the film thickness increases, the coercive force HC/ does not change significantly. Also, if we pay attention to the magnetization jump amount σj, the magnetization jump amount rises sharply when the film thickness is 0.075 μm and becomes 0, 0.
At a film thickness of 75 μm or more, a smooth downwardly convex parabolic shape is drawn. Furthermore, if we pay attention to the coercive force 11c in the vertical direction, the coercive force Hc rises rapidly in the film thickness range of 0.05 μm to 0.1 μm and reaches 90% in the film thickness of 0.1 μm or more.
Shows high coercive force of 008 or higher. From these results, the boundary between the small-grain crystal layer and the large-grain crystal layer is located at a film thickness of approximately 0.075 μm, and the small-grain crystal layer with a film thickness of 0.075 μm or less is located in the in-plane direction. and coercive force H in the vertical direction
c It is a so-called low coercive force layer with low ZtHc, and the large grain crystal layer with a film thickness of 0.075μ or more has a low coercive force HC/ in the in-plane direction, but a coercive force 1 in the perpendicular direction. The layer above −1c is a so-called high coercive force layer having a very high value, and is a layer suitable for perpendicular magnetic recording. Furthermore, the film thickness dimension (o, o
ysμ- or less), the coercive force Hc/, Hc↓ in the in-plane direction and perpendicular direction is low, and when the film thickness is larger than this (0,075μ- or more), the coercive force HC in the perpendicular direction increases rapidly. . If a magnetization jump also occurs due to this, it is presumed that two layers with different magnetic properties are formed in the Go-Cr-Nb thin film.

Next, add Ta as a third element to co-cr (1-1Q
The same phenomenon occurs in the at% addition range), and the results of the same experiment as in the case of adding Nb described above are shown in FIG. Figure 7 shows that the film thickness of the C0-Cr-Ta thin film is controlled by changing the sputtering time, and the in-plane coercive force HC/, the perpendicular coercive force Hc, and the magnetization jump amount σj at each film thickness are controlled. are drawn respectively. From the same figure, even when Ta is added to co-cr, Co
-Almost the same results as when Nb is added to Cr are obtained,
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 the small-grain crystal layer with a film thickness of 0.075 μm or less has a thickness in the in-plane direction and in the vertical direction. The coercive force HC/ and HC↓ are low (both Hc / and llc are 1700e or less), making it a so-called low coercive force layer.

In addition to this, on the vertical and in-plane coercive force 1-1c,
The difference in HC/ values is small and the layer is so-called isotropic. In addition, although the large-grain crystal layer with a film thickness of 0.075μ or more has a low coercive force HC/ in the in-plane direction, it has a very high coercive force 1-1c in the perpendicular direction (750Qe
above).

What should be noted in the above experiment is that the sputtering conditions and the added amounts of Nb and Ta are set to the values described above (Nb: 2 to 2).
10 at%, Ta: 1 to 10 at%), no magnetization jump occurs, but the Go-Cr-Nb'NJ film does not cause any magnetization jump.

A small grain size crystal layer and a large grain size crystal layer are also formed in the Go-Cr-Ta thin film and the co-Crs film (see the above-mentioned document). C where no magnetization jump occurs
An example of the hysteresis curve of the o-cr-Nbl film is shown in FIG. FIG. 8(A) is a hysteresis curve in the in-plane direction including a small-grain crystal layer and a large-grain crystal layer;
FIG. 8(B) shows an in-plane hysteresis curve of only the small-grain crystal layer, and FIG. 8(C) shows an in-plane hysteresis curve of only the large-grain crystal layer. From each figure, the residual magnetization Mrs/in the in-plane direction of the small grain crystal layer is the residual magnetization Mrc of the large grain crystal layer.
Since the residual magnetization Mr^ including both crystal layers is larger than /,
/ is more disadvantageous than when only the residual magnetization Mr c / of the large grain crystal layer is present, and the anisotropic magnetic field Hk becomes smaller. Furthermore, it is known that the small-grain crystal layer has poor orientation (large Δθ50), and also has a large in-plane coercive force HC/, making it unsuitable for perpendicular magnetic recording.

Here, as described above, a Go-Or-Nb WJ film and a co-Qr-T film having a small-grain crystal layer and a large-grain crystal layer are used.
When considering the Al film as a perpendicular magnetic recording medium, Go −
When attempting to perpendicularly magnetize a Cr-Nb thin film or a Go-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 previously thought that this would be a disadvantageous factor in cases where a magnetization jump occurs and in cases where a magnetization jump does not occur. In other words, in a small-grain crystal layer where a magnetization jump occurs, the coercive force Hc / and Hc in the in-plane direction and perpendicular direction are both extremely low (1700e or less), and it is thought that there is almost no perpendicular magnetization in this layer. It will be done.

Furthermore, even in a small-grain crystal layer when no magnetization jump occurs, the coercive force HC/ in the in-plane direction is larger than the coercive force HC/ when a magnetization jump occurs, but the coercive force HC/ in the perpendicular direction In the above case, 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 perpendicularly 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 is reduced.

This effect is remarkable in a magnetic head that includes a large in-plane component of magnetic flux, such as a ring core head.

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 are different from the conventional Go-
It has similar characteristics to the backing layer disposed between the Cr thin film and the base. That is, Go -Cr-Nb thin film and co -
In the Or-Ta N 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.

Accordingly, 'CCo -Or -Nb'WI film and C,o
A small-grain crystal layer formed when a single -Cr-Ta thin film is sputtered functions as a backing layer,
It is also possible to make the large grain crystal layer function as a perpendicular magnetization layer. However, in a single film of CoCrNb ii film and Go-Cr-Tapl film, C0-
The amount of Nb and Ta added to Cr is limited to a predetermined amount at which a magnetization jump occurs. Furthermore, CG is a ferromagnetic material and Nb is a non-magnetic material.

By adding Ta, 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 a Co-Cr-Nb thin film or a Go-Cr-Ta thin film is first formed on the base (approximately 0.1μ or less). , and the amount of Nb and Ta added is smaller than the condition value for the occurrence of magnetization jump, and the saturation magnetization is 1yl.
Go-Cr-Nbl film with large s or Go-
A large-grain crystal layer that directly contributes to perpendicular magnetic recording was formed by sputtering an 0r-Ta thin film. In the perpendicular magnetic recording medium having the above structure, Co-Cr-N is used as the small-grain crystal layer.
Fig. 9 Comparison of various magnetic properties when using a thin film with a Go -0r-Nb single JIIL film with a small amount of Nb added and a Go -Cr-Nb 4111N film with magnetization jump. The relationship between the recording wavelength of each ms and the reproduction output when magnetic recording and reproduction is performed on this perpendicular magnetic recording medium using a ring core head made of Sendust (registered trademark) is shown in the 10th table.
The figure also shows various magnetic properties when a Go-Cr-Ta thin film is used as a small-grain crystal layer with a small amount of Ta(7) added, a Go-Cr-Ta l1li thin film, and a magnetization jump. In comparison with Go-Cr, -Ta single-layer thin films, Figure 11 shows the recording wavelength and reproduction of each thin film when perpendicular magnetic recording and reproduction is performed on this perpendicular magnetic recording medium using a ring core head made of Sendust. The relationship between the outputs is shown in FIG. 13. From FIG. 9 and FIG. 11, Go-Cr-Nb and Go-Cr-Ta (hereinafter Go-Cr-'Nb) formed under conditions where magnetization jump occurs.
When collectively referring to C0-Cr-Ta, Go -Cr -N
C to which Nb or Ta is added in an amount smaller than the condition value for magnetization jump to occur on the small grain size crystal layer of (denoted as b(Ta)).
A perpendicular magnetic recording medium (hereinafter referred to as a two-layer medium) in which a large-grain crystal layer of o -Or -Nb (Ta) is formed is:
Go -Cr -Nb (
Ta) The saturation magnetization 1yls is larger than each thin film single-layer perpendicular magnetic recording medium, and the perpendicular coercive force)l
It also has a high value of c, and has characteristics suitable for perpendicular magnetization. On the other hand, as shown in FIG. 10, the reproduction output and recording wavelength characteristics are CO-Or-
Perpendicular magnetic recording media with NbR film (hereinafter referred to as magnetization jump single layer media) and Co-Cr with a small amount of added Nb
Compared to a -Nb thin film perpendicular magnetic recording medium (hereinafter abbreviated as a low-doping single-layer medium), a dual-layer medium exhibits higher values in all recording wavelength regions and can obtain stronger reproduction output.

Particularly in the short wavelength range (recording wavelength range of 1μll-0.2μm), although magnetization jump single-layer media and low-doping single-layer media increase their reproduction output, double-layer media have even higher reproduction output efficiency. 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. Note that even in the Go-Cr-Ta two-layer medium, the first
Similar results were obtained as shown in Figure 3. Further, FIGS. 14 and 15 show M-H hysteresis curves in each in-plane direction when a magnetic field of 15 KOe is applied to each of the two-layer media shown in FIGS. 9 and 10 above. Note that Figure 14 is
The characteristics of the two-layer medium shown in the figure (the lower layer is made of Go-Cr-Nb) are shown, and FIG. 15 shows the characteristics of the two-layer medium shown in FIG. 11 (the lower layer is made of C).

-Cr-Ta). As shown in both figures, the in-plane M-H hysteresis curve of each two-layer medium exhibits characteristics with a so-called magnetization jump, which has a sharp rise near the origin, and the magnetization jump temperature is as shown in Fig. 1. This is larger than the magnetization jump of the Nb single-layer medium shown in (the same result is obtained when compared with the Ta single-layer medium). In other words, the in-plane M-H hysteresis characteristic of the two-layer medium shows a more rapid rise near the origin compared to each single-layer medium, and the perpendicular magnetic field of the two-layer medium with in-plane M-H hysteresis characteristic As shown in FIGS. 10 and 13, the recording/reproducing characteristics show higher efficiency than each single layer medium.

The reason why the above phenomenon occurs will be deduced below using FIG. 12. When a Go-Cr-Nb (Ta) magnetic material is sputtered to a film thickness of about 0.1 μm on a base 1 made of polyimide or the like while satisfying the conditions for a magnetization jump to occur, a CO-Cr-Nb film is formed as described above. (Ta >
It is considered that 8M has a small-grain crystal layer 2 formed over almost its entire surface.

This small grain size crystal 12 has a small coercive force HC/ in the in-plane direction,
(and coercive force in the perpendicular direction) is an isotropic layer with little difference from that on lc. Therefore, the small-grain crystal layer 2 can perform substantially the same function as a so-called underlayer.

In the upper part of the small-grain crystal layer 2, a Co-Cr layer with added amounts of Nb and Ta smaller than the condition value for magnetization jump is formed.
-Nb (Ta) magnetic material is sputtered to a thickness of about 0.1 μm. Co-Cr-Nb (Ta
) When the magnetic material is sputtered onto the small-grain crystal layer 2, since both have similar properties in terms of crystal structure and composition, C with a small amount of added Nb and Ta is added at the boundary between the two magnetic materials. .

-Cr-Nb (Ta) 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 has high saturation magnetization MS. It is thought that large grain size crystals 113, which have a strong coercive force in the vertical direction and directly contribute to perpendicular magnetization, grow immediately. In addition, in the Go-Cr-Nb(Ta) thin film forming the large-grain crystal layer 3, the amounts of Nb and Ta added can be arbitrarily determined without being restricted by the condition value that causes a magnetization jump as in the small-grain crystal layer 2. can be selected. As described above, although the saturation magnetization Ms of CO is reduced by the addition of Nb and Ta, the axis of easy magnetization of Co is strongly oriented in the perpendicular direction. Therefore, by appropriately selecting the amounts of Nb and Ta added, it is possible to maintain high saturation magnetization MS while strongly orienting the axis of easy magnetization of CO in the perpendicular direction. Go - Cr - formed on the small grain size crystal layer 2
The amounts of Nb and Ta added to the Nb(Ta)WI film 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 low coercive force and isotropy. It is thought that the magnetic flux advances in the in-plane direction within the small-grain crystal layer 2 having the magnetic head 5, and the magnetic flux is suddenly absorbed by the magnetic pole portion of the magnetic head 5, causing perpendicular magnetization to the large-grain crystal 1i3. 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 FJ3 having a high saturation magnetization MS at a predetermined perpendicular magnetic recording position, so that the large grain The diameter crystal layer 3 is perpendicularly magnetized with a large residual magnetization.

When perpendicular magnetic recording is performed as described above, the large-grain crystal layer 3
As shown in FIG. 16, a plurality of magnets with opposite magnetic directions are alternately formed at predetermined bit intervals. and,
A magnetic flux (indicated by an arrow in FIG. 16) that connects the lower ends of the magnets formed adjacent to each other is formed in the small-grain crystal layer 2 at the lower ends of the plurality of magnets formed, and this is magnetized. be done. This eliminates the demagnetizing effect of each adjacent magnet, making it possible to increase the regenerated force. In addition, as mentioned above, the II film thickness of the small-grain crystal WI2 is very thin, approximately 0.1 μm, so the film thickness of the entire perpendicular magnetic recording medium can be reduced, and the mechanical strength of the magnetic layer can be reduced. The flexibility is increased, so-called contact with the magnetic head 5 is improved, and the sputtering time during manufacturing can be shortened, making it possible to manufacture perpendicular magnetic recording media at low cost and with high productivity. In addition, it is known that the thermal elongation of a recording medium can be adjusted by adding Nb and Ta. Therefore, by appropriately selecting the amount of Nb and Ta added, the thermal expansion coefficient can be adjusted. It is possible to easily produce a recording medium that can be adjusted and has less curl. In addition, the coercive force HC/ in the in-plane direction of the small-grain crystal layer 2 is 1 from FIGS. 6 and 7.
Since it is about 00e to 500e and is not an extremely small value with respect to the coercive force Hc of the large grain crystal layer 3, good perpendicular magnetic recording and reproduction can be performed without generating impulsive Barkhausen noise.

Effects of the Invention As described above, according to the perpendicular magnetic recording medium of the present invention, there is a lower layer on a base containing cobalt, chromium, and other elements in a predetermined circle, and a lower layer containing cobalt, chromium, and the other elements mentioned above on this lower layer. By forming an upper layer containing the same element in a smaller amount than the predetermined amount, the perpendicular magnetic recording medium has an in-plane M-H represented by a curve with a sharp rise near the origin.
By configuring it to have hysteresis characteristics, the perpendicular magnetic recording medium has a lower layer on the base that has a small in-plane anti-Wift and is isotropic, and a lower layer that has a high saturation magnetization and a large perpendicular coercive force. Because it has a two-layer structure with an upper layer, the magnetic flux emitted from the magnetic head easily enters the lower layer, which has low coercive force and isotropy, and propagates in the horizontal direction, causing high saturation magnetization. It penetrates the upper layer, which has a high coercive force, and is suddenly and sharply attracted to the magnetic pole of the magnetic head, so strong residual magnetization occurs in the upper layer, making it possible to perform perpendicular magnetic recording and reproduction that can realize high reproduction output. In addition, excellent perpendicular magnetization is achieved especially for short recording wavelengths, making it possible to obtain good reproduction output, and the lower layer has a magnetization jump, that is, the coercive force in the in-plane direction is small, and it is isotropic. This layer reliably functions as a so-called backing layer, and its coercive force is not unnecessarily small compared to the coercive force of the upper layer, so it does not generate impulsive Barkhausen noise and has good perpendicular magnetic properties. In addition to this, the magnetization direction is alternately changed between layers with low coercive force and layers with high coercive force, and W41! A magnetic flux is formed that connects the ends of the plurality of magnetized magnets, and this magnetization eliminates the demagnetizing effect of each adjacent magnet, increasing the reproduction output. Since the thickness is very thin, the mechanical flexibility of the magnetic layer is large, so that so-called contact with the magnetic head is good, and the time for forming the magnetic layer can be shortened, so it has various effects as described above. Furthermore, Nb and 7a in the upper layer enable mass production of perpendicular magnetic recording media at low cost.
The amount of addition can be arbitrarily selected, and by selecting the addition amount to an appropriate amount that maintains high saturation magnetization while strongly orienting the axis of easy magnetization of CO in the perpendicular direction, the reproduction output can be greatly improved. It has features such as being able to realize perpendicular magnetic recording and reproducing, and being able to adjust the coefficient of thermal expansion, making it possible to easily manufacture a perpendicular magnetic recording medium with little curl.

[Brief explanation of the drawing]

FIG. 1 shows 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 shows a hysteresis curve of a small-grain crystal layer. Figures 3 to 5 are diagrams for explaining the reason why magnetization jumps occur; Figure 6 is a diagram showing that the Co-Cr-Nb thin film has a two-layer structure and the magnetic properties of each layer; The figure shows the two-layer structure of Co-Cr-Ta WIli and the magnetic properties of each layer.
The figure shows Go -Or -Nb where no magnetization jump occurs.
A diagram showing an example of a hysteresis curve of a thin film, FIG. 9 shows various magnetic properties when Go-Cr-Nb WIli is used as a small-grain crystal layer.
10 is a diagram showing the relationship between recording wavelength and reproduction output of each thin film shown in FIG. 9; Figure 11 shows various magnetic recording properties when using Co-Cr-Ta WIWA as a small-grain crystal layer.
a single layer 1111! and Go where magnetization jump occurs
-Cr-Ta monoim film is shown in comparison, FIG.
Each i1 [1! Figure 14 is a diagram showing the relationship between the recording wavelength and reproduction output of the two-layer medium shown in Figure 9.
A diagram showing the hysteresis characteristics, FIG. 15 is a diagram showing the in-plane M-H hysteresis characteristics of the two-layer medium shown in FIG.
FIG. 6 is a diagram for explaining the magnetic flux that communicates between the lower ends of the plurality of magnets magnetized in the large-grain crystal layer formed in the small-grain crystal layer. DESCRIPTION OF SYMBOLS 1...Base, 2...Small grain size crystal layer, 3...Large grain size crystal layer, 4...Two-layer medium, 5...Magnetic head. Patent applicant: Victor Japan Co., Ltd. Figure 2

Claims (2)

[Claims] (1) A lower layer made of cobalt and chromium containing a predetermined amount of other elements on the base, and a cobalt layer formed on the lower layer,
A perpendicular magnetic recording medium comprising an upper layer containing chromium and the same element as the other element in an amount smaller than the predetermined amount, the in-plane M- A perpendicular magnetic recording medium characterized by having H hysteresis characteristics. (2) The perpendicular magnetic recording medium according to claim 1, wherein the other element added to the cobalt and chromium is at least one of niobium and tantalum.