JPH07182644A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve vertical coercive force and residual flux density by making the axis of facilitating magnetization approach a magnetic layer vertically in a magnetic recording medium having a magnetic layer formed by a slant evaporation method. CONSTITUTION:A magnetic layer is arranged on a base body. The magnetic layer has more than one layer of ferromagnetic metal thin films comprising columnar crystal particles formed by a slant evaporation method and a non- magnetic thin film existing between adjacent ferromagnetic metal thin films. The saturation magnetic flux density Bs of the magnetic layer is 2,000-4,000G and the thickness of the non-magnetic thin film is 0.15-0.50 times as much as an average value of the thickness of the ferromagnetic metal thin film. The direction of crystal growth of all the ferromagnetic metal thin films is almost the same and when the average value of an angle is represented by theta between the direction of the crystal growth of the films and the main face of the base body and the angle by E between the direction of an axis of facilitating magnetization of the magnetic layer and the main face of the base body. E-theta>0 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having as a magnetic layer a ferromagnetic metal thin film composed of columnar crystal grains formed by an oblique vapor deposition method.

[0002]

2. Description of the Related Art In recent years, magnetic recording media have been required to have a high density. A ferromagnetic metal thin film made of an alloy containing Co as a main component and containing Ni or the like has a large saturation magnetic flux density, a high coercive force, and is easy to deposit, so that it has been actively studied as a magnetic layer for high-density recording. The Co-Ni thin film is usually formed by the oblique vapor deposition method. The oblique vapor deposition method is a method of performing vapor deposition by irradiating a stationary ferromagnetic metal source with an electron beam or the like while transporting a non-magnetic substrate along with the surface of a rotating cylindrical cooling drum, which has a large area. Since the film can be formed at once, it is suitable for manufacturing a magnetic tape. It has been proposed to stack two or more ferromagnetic metal thin films to form a multilayer structure by such an oblique vapor deposition method (Japanese Patent Laid-Open No. 61-145722 and Japanese Patent Laid-Open No. 4-205).
813 publication).

In the oblique vapor deposition method, the angle formed by the direction in which the ferromagnetic metal is incident and the normal line to the surface of the non-magnetic substrate is called the incident angle. Usually, vapor deposition is performed so that the incident angle gradually decreases from the start to the end of vapor deposition. The vapor deposition rate is lowest at the start of vapor deposition with the largest incident angle, and the vapor deposition rate rapidly increases as the incident angle becomes smaller. Therefore, the columnar crystal grains in the ferromagnetic metal thin film are nearly parallel to the surface of the non-magnetic substrate on the non-magnetic substrate side, and rapidly rise in an arc shape with increasing distance from the surface of the non-magnetic substrate. The direction of the easy axis of magnetization of such a ferromagnetic metal thin film depends on the inclination of the columnar crystal grains.

As a magnetic recording method capable of high density recording,
Perpendicular magnetic recording is known. In perpendicular magnetic recording,
The influence of the demagnetizing field in the in-plane direction of the magnetic layer is avoided, and high density recording becomes possible. Conventionally, a single magnetic pole head is generally used for perpendicular magnetic recording, but it has been reported that ring head recording can be performed by tilting the easy axis of magnetization slightly from the perpendicular, and particularly excellent high density recording characteristics can be obtained. (The Journal of Japan Applied Magnetics vol.16, supplement, No.S1, pp51 (1
992)}.

[0005]

SUMMARY OF THE INVENTION According to the present invention, in a magnetic recording medium having a magnetic layer formed by an oblique vapor deposition method, an easy axis of magnetization is brought close to a direction perpendicular to the magnetic layer, and a coercive force and a residual magnetic flux in the perpendicular direction are provided. The purpose is to improve the density.

[0006]

These objects are achieved by the present invention described in (1) to (7) below. (1) It has a magnetic layer on a substrate, and this magnetic layer exists between two or more layers of ferromagnetic metal thin films composed of columnar crystal grains formed by oblique vapor deposition and adjacent ferromagnetic metal thin films. And a saturation magnetic flux density Bs of the magnetic layer.
Is 2000 to 4000 G, and the thickness of the non-magnetic thin film is 0.15 to 0.50 of the average value of the thickness of the ferromagnetic metal thin film.
The average growth direction of the columnar crystal grains of all ferromagnetic metal thin films is almost the same, and the average value of the angle between the growth direction of the columnar crystal grains of each ferromagnetic metal thin film and the main surface of the substrate is θ. (Where 0 <θ <90 °), and the angle formed by the direction of the easy axis of magnetization of the magnetic layer and the main surface of the substrate is E (where 0 <
A magnetic recording medium, wherein E-θ> 0 ° when E <90 °). (2) The average thickness of the ferromagnetic metal thin film is 1200 A
The magnetic recording medium according to (1) above, which is as follows. (3) The magnetic recording medium according to (1) or (2), wherein the thickness of the non-magnetic thin film is 100 A or more. (4) The magnetic recording medium according to any one of (1) to (3) above, wherein the non-magnetic thin film has an oxide of an element contained in the ferromagnetic metal thin film as a main component. (5) The magnetic recording medium according to any one of (1) to (4), wherein the ferromagnetic metal thin film contains Co as a main component. (6) The ratio of the coercive force in the perpendicular direction of the magnetic layer (Hc ⊥) to the coercive force in the in-plane direction of the magnetic layer (Hc //) is (Hc ⊥) / (Hc //)≧1.1. )-(5) magnetic recording medium. (7) The ratio of the residual magnetic flux density in the perpendicular direction of the magnetic layer (Br ⊥) to the residual magnetic flux density in the in-plane direction of the magnetic layer (Br //) is (Br ⊥) / (Br //)≧1.1 The magnetic recording medium according to any one of (1) to (6).

[0007]

In the single-layer ferromagnetic metal thin film formed by the oblique vapor deposition method, the angle formed by the direction of the easy axis of magnetization and the main surface of the substrate is demagnetized because of the demagnetizing field and the growth direction of the columnar crystal grains and the substrate. It is smaller than the angle formed by the main surface. On the other hand, when two layers of ferromagnetic metal thin films are laminated so that the crystal growth directions are the same, and a nonmagnetic thin film is provided between both films, the interaction between both ferromagnetic metal thin films facilitates magnetization. The direction of the axis approaches the vertical direction.

In the present invention, in such a multilayer magnetic recording medium, the interaction between the ferromagnetic metal thin films is controlled by setting the thickness of the nonmagnetic thin film within a predetermined range, and the saturation magnetic flux density Bs of the magnetic layer is controlled. The influence of the demagnetizing field is controlled by setting the range to a predetermined range. As a result, since the easy axis of magnetization can be brought close to the direction perpendicular to the magnetic layer and E-θ can be set within the above range, a magnetic recording medium suitable for perpendicular magnetic recording is realized. In the magnetic recording medium of the present invention, for example, the coercive force (Hc ⊥) in the perpendicular direction of the magnetic layer and the coercive force (Hc in the in-plane direction of the magnetic layer).
The ratio with //) can be (Hc ⊥) / (Hc //)≧1.1, and the residual magnetic flux density (Br
The ratio of ⊥) to the residual magnetic flux density in the in-plane direction of the magnetic layer (Br //) can be (Br ⊥) / (Br //)≧1.1.

Although it has been conventionally proposed to provide a non-magnetic thin film between obliquely vapor-deposited ferromagnetic metal thin films, a non-magnetic thin film having a predetermined thickness is provided after limiting the saturation magnetic flux density of the magnetic layer. , And there is no suggestion to bring the easy axis of magnetization closer to the perpendicular direction, nor is there any suggestion. For example, JP-A-61-145722 and JP-A-4-20 mentioned above.
Japanese Patent No. 5813 discloses a magnetic layer in which a ferromagnetic metal thin film is grown in the same direction by oblique vapor deposition,
Although there is a description of a non-magnetic thin film between ferromagnetic metal thin films, the absolute value of the saturation magnetic flux density is not disclosed. Japanese Unexamined Patent Publication No. 61-145722 aims to improve the corrosion resistance of the magnetic layer, and does not describe the perpendicular magnetic recording.

Japanese Unexamined Patent Publication (Kokai) No. 4-259909 proposes to control the thickness of a non-magnetic thin film between ferromagnetic metal thin films formed by an oblique vapor deposition method, but the purpose of the invention described in the publication is to: This is to obtain a high reproduction output and a high C / N from a long wavelength to a short wavelength. The publication describes that oxygen is introduced into the vacuum chamber so that the saturation magnetization becomes about 4500 gauss when forming the magnetic layer. In the example of the publication, the lower magnetic layer and the upper magnetic layer are both 4
It is more than 500 gauss, which is different from the present invention. Further, this publication does not explicitly state that the crystal growth directions of all the ferromagnetic metal thin films are the same.

The reason why the saturation magnetic flux density of the magnetic layer is limited in the present invention is that the strength of the diamagnetic field in the direction perpendicular to the magnetic layer greatly changes depending on the value of the saturation magnetic flux density. Conventionally,
In an in-plane recording medium that utilizes magnetization in the in-plane direction of the magnetic layer, it is required to increase the saturation magnetic flux density of the magnetic layer, and this also applies to the in-plane recording medium using the oblique deposition method. However, in the magnetic layer formed by the oblique deposition method, the easy axis of magnetization approaches the in-plane direction when the saturation magnetic flux density increases, so that it is not suitable for perpendicular magnetic recording even though it has high performance for in-plane recording. .

[0012] By the way, a report of "Magnetic structure analysis of multilayer vapor-deposited tape" is described in the Technical Bulletin, MR91-2, pp7 (1991). In this report, magnetic structure analysis is performed on a vapor deposition tape having two magnetic layers having the same crystal growth direction and a non-magnetic layer between them. Report 10
FIG. 8B on the page shows that in the same-direction laminated film model, the easier axis of magnetization approaches the perpendicular as the nonmagnetic layer becomes thinner and the interlayer interaction becomes larger. The saturation magnetic flux density of the magnetic layer of the model in the figure is 400 emu / cm ³ (about 5000 G), which is different from the present invention. In this model, the interlayer coefficient c {thickness of each magnetic layer / (thickness of nonmagnetic layer × 2)} is 0, that is, when the nonmagnetic layer thickness is infinite and there is no interaction between both magnetic layers, Due to the influence of the demagnetizing field, the easy axis of magnetization is oriented in the in-plane direction. As the non-magnetic layer becomes thinner, the easy axis of magnetization approaches the vertical direction, and when the interlayer coefficient c is about 2.5, the crystal growth direction and the easy axis of magnetization almost coincide with each other. As the magnetic layer thickness decreases), the easy axis of magnetization approaches the perpendicular direction.

As described above, the same report describes that the easy axis of magnetization can be made close to perpendicular by thinning the non-magnetic layer existing between the magnetic layers. However, this uses a simulation model, which is very different from the actual magnetic recording medium. In the same report, the simultaneous rotation model is used for the magnetic structure analysis, and regarding the interaction between the upper magnetic layer and the lower magnetic layer, the exchange interaction is ignored,
Only dipole interactions are considered. However, in an actual magnetic recording medium, exchange interaction between magnetic layers and interaction between columnar crystal grains in the same magnetic layer have an influence. Such a discussion is impossible.

On the other hand, according to the present invention, in order to improve the magnetic characteristics in the perpendicular direction in an actual magnetic recording medium,
It was determined that the thickness of the non-magnetic thin film should be 0.15 times or more that of the ferromagnetic metal thin film. By suppressing the saturation magnetic flux density of the magnetic layer to 4000 G or less, good magnetic characteristics in the perpendicular direction can be obtained even when the nonmagnetic thin film is as thick as 0.50 times as thick as the ferromagnetic metal thin film. Being able to make the non-magnetic thin film thick in this way is advantageous in high-density recording. For high-density recording, it is necessary to reduce the thickness of one ferromagnetic metal thin film layer. For example, when the ferromagnetic metal thin film has a thickness of less than 500 A, c = 2.5 in the above model. Then, the thickness of the nonmagnetic thin film will be less than 100 A. It is extremely difficult to form such a thin non-magnetic layer with a uniform thickness, and stable mass production is difficult. In particular, when three or more magnetic layers are laminated, the thickness per magnetic layer is further reduced, so that such a problem becomes more remarkable.

[0015]

Specific Structure The specific structure of the present invention will be described in detail below.

The magnetic recording medium of the present invention has a magnetic layer on the substrate. The magnetic layer has a ferromagnetic metal thin film composed of columnar crystal grains formed by oblique vapor deposition and a nonmagnetic thin film existing between adjacent ferromagnetic metal thin films.

The columnar crystal grains of each ferromagnetic metal thin film in the magnetic layer grow in substantially the same direction. In the present invention, that the growth directions of the columnar crystal grains are substantially the same direction means that the growth direction of each film exists on one side of the plane when a plane perpendicular to the traveling direction of the magnetic head is considered. Means In order to make the growth direction of each film have such a relationship,
For example, when the oblique vapor deposition method described later is used, the substrate traveling directions during vapor deposition may all be the same direction. In the present invention, it is not necessary that the growth direction of each film and the maximum incident angle and the minimum incident angle of the ferromagnetic metal particles at the time of forming each film are the same.

The average value of the angle between the growth direction of the columnar crystal grains of each ferromagnetic metal thin film and the principal surface of the substrate is θ, and the angle between the easy axis of magnetization of the magnetic layer and the principal surface of the substrate is E. In the present invention, E-θ> 0 °, preferably E-θ = 10.
-22 °. However, 0 <θ <90 °, 0 <E <9
It is 0 °. Attempting to obtain E-θ exceeding 22 ° is not preferable because the saturation magnetic flux density of the magnetic layer must be lowered.

The average value θ of the angle between the growth direction of the columnar crystal grains and the main surface of the substrate is measured as follows.

First, the magnetic recording medium is cut along a plane including the growth direction of columnar crystal grains (generally, a plane perpendicular to the main surface of the medium and including the traveling direction of the magnetic head). In the cross section, columnar crystal grains forming each ferromagnetic metal thin film appear in an arc shape. The angle formed by the side surface of the columnar crystal grains appearing in this cross section (the boundary line between adjacent columnar crystal grains) and the main surface of the substrate was measured for at least 100 columnar crystal grains for each ferromagnetic metal thin film, and the Obtain their average value in the metal thin film. Each of these average values is taken as the angle formed by the growth direction of the columnar crystal grains in each ferromagnetic metal thin film and the main surface of the substrate, and the average of these is taken as θ. The measurement position of θ is an intermediate point in the thickness direction of the ferromagnetic metal thin film.

The growth direction of the columnar crystal particles depends on the incident direction of the ferromagnetic metal particles in the oblique vapor deposition method, and particularly depends on the minimum incident angle. In the present invention, the range of θ is not particularly limited and may be appropriately selected according to the required coercive force, residual magnetic flux density, etc., but in order to obtain high coercive force and high residual magnetic flux density in the direction perpendicular to the magnetic layer, Preferably θ = 35 to 60 °
And If θ is too small, the residual magnetic flux density will be insufficient, and if θ is too large, the coercive force will be insufficient.

The angle E formed by the direction of the easy axis of magnetization of the magnetic layer and the main surface of the substrate can be determined by VSM or the like.

The saturation magnetic flux density Bs of the magnetic layer is 2000 to
It is 4000 G, preferably 3000-4000 G.
If Bs is too small, the reproduction output decreases, and if Bs is too large, the demagnetizing field becomes too large, which hinders the action of bringing the easy axis of magnetization closer to the perpendicular direction.

The non-magnetic thin film existing between the ferromagnetic metal thin films has a function of adjusting the magnetic interaction between the ferromagnetic metal thin films on both sides thereof.

The thickness of the non-magnetic thin film is 0.15 to 0.50 times the average value of the thickness of the ferromagnetic metal thin film. The average thickness of the ferromagnetic metal thin film is a value obtained by dividing the total thickness of the ferromagnetic metal thin films in the magnetic layer by the number of laminated layers. If the non-magnetic metal thin film is too thin with respect to the ferromagnetic metal thin film, the exchange interaction between the ferromagnetic metal thin films becomes large, and if the non-magnetic thin film is too thick with respect to the ferromagnetic metal thin film, the ferromagnetic materials on both sides The interaction between the metal thin films is almost eliminated, and in both cases, the effect of the present invention cannot be realized, as in the case where the ferromagnetic metal thin film is a single layer.

The thickness of the non-magnetic thin film is preferably 100 A.
As described above, more preferably 150 A or more. If the non-magnetic thin film is too thin, it will be difficult to stably obtain a uniform thickness when the ferromagnetic thin film is formed by a method of introducing oxygen as described later. Further, the influence of exchange interaction between the ferromagnetic metal thin films becomes large, and the easy axis of magnetization tends to approach the plane of the magnetic layer. The thickness of the non-magnetic thin film is
It is preferably 300 A or less.

The non-magnetic thin film preferably contains, as a main component, an oxide of an element contained in the ferromagnetic metal thin film. Such a non-magnetic thin film can be formed by, for example, a method of introducing oxygen gas into a film forming atmosphere when a ferromagnetic metal thin film is formed by an oblique evaporation method as described later. With this method, high productivity can be obtained, and a small amount of oxygen is also taken into the ferromagnetic metal thin film to improve the coercive force.

In the nonmagnetic thin film containing an oxide formed by such a method, the oxygen concentration gradually changes in the vicinity of the interface with the ferromagnetic metal thin film. Is defined as follows. That is, if the average value of the oxygen concentration at the midpoint in the thickness direction of the two ferromagnetic metal thin films existing on both sides of the non-magnetic thin film is Mave and the maximum oxygen concentration of the non-magnetic thin film is Nmax, the maximum of the non-magnetic thin film is The thickness of the region containing the oxygen concentration point and having the oxygen concentration of (Nmax + Mave) / 2 or more is defined as the thickness of the non-magnetic thin film. The maximum oxygen concentration Nmax of the non-magnetic thin film is not particularly limited,
It is preferably 20 atomic% or more. By setting Nmax within this range, it becomes easy to adjust the interaction between the ferromagnetic metal thin films and thereby control the direction of the easy axis of magnetization.
The oxygen concentration in the non-magnetic thin film can be measured by performing elemental analysis such as Auger spectroscopy while etching the magnetic layer.

The nonmagnetic thin film according to the present invention is not limited to the above-mentioned thin film containing an oxide as a main component, but includes various nonmagnetic compounds other than an oxide or a nonmagnetic metal as a main component. Good. Various compounds other than oxides are also preferably compounds of elements contained in the ferromagnetic metal thin film. The thickness of the non-magnetic thin film in this case may be determined according to the thickness measurement of the non-magnetic thin film containing oxide as a main component by measuring the nitrogen or carbon concentration in the magnetic layer.

The non-magnetic thin film may be present not only between the adjacent ferromagnetic metal thin films, but also between the substrate and the lowermost ferromagnetic metal thin film, or on the uppermost ferromagnetic metal thin film. .

The average value of the thickness of the ferromagnetic metal thin film is 120
It is preferably 0 A or less, and the thickness of each ferromagnetic metal thin film is also preferably within this range. If the ferromagnetic metal thin film is too thick, the coercive force cannot be increased and noise also increases. The thickness of the ferromagnetic metal thin film is usually 30
It is preferably 0 A or more. If the ferromagnetic metal thin film is too thin, it becomes difficult to control the film thickness, and further, the total magnetization amount becomes small and the output decreases.

The thickness of the magnetic layer comprising the ferromagnetic metal thin film and the non-magnetic thin film as described above is not particularly limited, but in order to obtain the output required as a recording medium, it is usually 1000 A or more. preferable. The magnetic layer is usually 25
It is preferably set to 00 A or less. If the magnetic layer is too thick, recording demagnetization and thickness loss increase, and the output decreases.

There is no particular limitation on the number of layers of the ferromagnetic metal thin film, and in consideration of magnetic characteristics and productivity, a structure of two layers, three layers or four layers or more may be appropriately selected.

In the present invention, the ferromagnetic metal thin film is preferably a Co-based alloy containing Co as a main component, and the Co content in the ferromagnetic metal thin film is preferably 60 atom% or more. Co-based alloys include Co and Ni
Alloys containing as the main component or containing Co, Ni and Cr as the main components are preferred.

Each ferromagnetic metal thin film is formed by an oblique vapor deposition method. There is no particular limitation on the oblique vapor deposition apparatus and method, and ordinary ones may be used.

In the oblique vapor deposition method, for example, a long film-shaped non-magnetic substrate fed from a supply roll is sent along with the surface of a rotating cooling drum to perform oblique vapor deposition from one or more stationary metal sources, It is to be wound up on a winding roll. In this case, the incident angle of the ferromagnetic metal particles continuously changes from the maximum incident angle θmax at the beginning of vapor deposition to the final minimum incident angle θmin. Then, columnar crystal grains of ferromagnetic metal containing Co as a main component grow in an arc shape on the surface of the non-magnetic substrate,
Line up. When the magnetic layer has a multilayer structure, this step is repeated.

The method for forming the non-magnetic thin film is not particularly limited, but if oxygen gas is introduced into the film forming atmosphere to perform vapor deposition, the non-magnetic thin film containing an oxide of a ferromagnetic metal thin film constituent element as a main component. Can be formed extremely easily.

In addition, a non-magnetic thin film containing an oxide as a main component can be formed by a method of surface-treating the surface of the ferromagnetic metal thin film with oxygen gas or its plasma.

Alternatively, Al, Cr, Ag, Au, P
The step of depositing a non-magnetic thin film containing a non-magnetic metal such as t, Ti or W as a main component may be provided independently after forming the ferromagnetic metal thin film.

There are no particular restrictions on the material of the substrate used in the present invention so long as it is non-magnetic, and various films, such as polyethylene terephthalate, which can withstand the heat of deposition of the ferromagnetic metal thin film can be used. In addition, JP-A-63-1031
Various materials described in Japanese Patent No. 5 can be used.

It is preferable that minute protrusions are provided on the surface of the substrate used in the present invention. Since the magnetic layer is a vapor-deposited film and is extremely thin, the properties of the substrate surface appear directly on the magnetic layer surface. Therefore, if minute protrusions are provided on the surface of the substrate, minute protrusions can appear on the surface of the magnetic layer.
The protrusions on the surface of the magnetic layer reduce the friction of the magnetic layer, improve the running property when formed into a tape, and enhance the durability of the medium.

The nature and formation method of the minute protrusions on the surface of the substrate are not particularly limited, but the arrangement pattern of the protrusions and the surface roughness of the substrate after the formation of the protrusions affect the magnetic characteristics of the magnetic layer, particularly the coercive force. It is preferable to provide the protrusions by arranging the fine particles on the surface of the substrate.

Various known top coat layers are preferably provided on the magnetic layer of the magnetic recording medium of the present invention to protect the magnetic layer and improve corrosion resistance. Further, in order to secure the running property when formed into a tape, it is preferable to provide various known back coat layers on the side opposite to the magnetic layer of the non-magnetic substrate.

The magnetic recording medium of the present invention is suitable for various types of perpendicular magnetic recording in which magnetization is performed in the direction perpendicular to the magnetic layer. It is also suitable for magnetic recording having a large amount of perpendicular magnetization component, for example, short wavelength recording using a ring head. Further, it is preferably applicable to both analog magnetic recording and digital magnetic recording.

[0045]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

[Example 1] From a supply roll to a substrate (thickness: 7)
(μm polyethylene terephthalate) was fed out and moved along the peripheral surface of the rotating cylindrical cooling drum, the ferromagnetic metal was obliquely vapor-deposited to form a lower ferromagnetic metal thin film, and the film was wound on a winding roll. . Then, the substrate was rewound from the winding roll to the supply roll, and the upper ferromagnetic metal thin film was obliquely vapor-deposited on the lower ferromagnetic metal thin film to obtain a magnetic recording medium sample. At the time of forming the ferromagnetic metal thin films of the upper and lower layers, a mixed gas of Ar gas and O ₂ gas was caused to flow in the vacuum chamber, and the pressure in the vacuum chamber was kept at 10 ⁻⁴ Torr.
The mixed gas was made to flow so as to blow onto the substrate in the portion to be vapor-deposited near the minimum incident angle. By spraying this mixed gas, a nonmagnetic thin film was formed on the interface between the lower layer and the upper layer and on the surface layer of the upper layer.

For comparison, after forming the ferromagnetic metal thin film of the lower layer, the substrate is unrolled from the winding roll without unwinding to form the ferromagnetic metal thin film of the upper layer, and the average growth direction of the columnar crystal grains is increased. Samples in which the upper and lower layers were in opposite directions were also prepared.

A plurality of samples were prepared by changing the O ₂ gas concentration in the mixed gas.

A ferromagnetic metal having a composition of Co 90 atomic% and Ni 10 atomic% was used for forming the upper layer and the lower layer of each sample.

Table 1 shows the upper layer thickness, the lower layer thickness, the average value of the upper layer thickness and the lower layer thickness (t _m ), the thickness of the nonmagnetic thin film (t _n ), and t _n / t _m of each sample. Show. The thickness of the nonmagnetic thin film was obtained by measuring the oxygen concentration distribution in the magnetic layer by Auger spectroscopic analysis, and based on this result, the method described above. In Table 1, the sample in which the upper layer of the ferromagnetic metal thin film is vapor-deposited after the substrate is rewound is defined as “in the same direction”.
Further, a sample in which the ferromagnetic metal thin film of the upper layer is vapor-deposited without rewinding the substrate is shown as "reverse direction".

For each sample, θ was measured by the method described above. The number of columnar crystal grains measured was 100 for each ferromagnetic metal thin film. The results are shown in Table 1.

For each sample, the angle E formed by the direction of the easy axis of magnetization and the main surface of the substrate was determined by VSM. Angle E
And E-θ are shown in Table 1.

For each sample, Bs, (H
c ⊥), (Hc //), (Br ⊥), (Br //) are measured, and coercive force ratio (Hc ⊥) / (Hc //) and residual magnetic flux density ratio (Br ⊥) / (Br / /) Was asked. The results are shown in Table 1. The maximum magnetic field strength when measuring magnetic properties is 1
It was set to 0 kOe.

The electromagnetic conversion characteristics of each sample were measured. The electromagnetic conversion characteristics of Sony E of Hi8 standard VTR
The RF output when a single signal of 7 MHz was recorded using V-S900 was compared with the RF output of the reference tape, and the evaluation was made according to the following evaluation criteria. 7 MH in Hi8 standard VTR
The z signal has a high ratio of the perpendicular magnetization component and is suitable for evaluating the electromagnetic conversion characteristics of the magnetic recording medium in the perpendicular direction. The results are shown in Table 1 as "electric characteristics".

⊚: 2.0 dB ≦ RF output ◯: 0 dB ≦ RF output <2.0 dB Δ: −1.0 dB ≦ RF output <0 dB ×: RF output <−1.0 dB

[0056]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear. That is, in the sample No. 12 having a saturation magnetic flux density Bs exceeding the range of the present invention, the sample No. 13 having a thickness ratio t _n / tm _less than the range of the present invention, and the sample No. 14 of the backward vapor deposition, all of the E- θ is negative and both the coercive force ratio and the residual magnetic flux density ratio are low. On the other hand, in the samples of the present invention, good results were obtained.

Even when three or more ferromagnetic metal thin films are laminated, the relationship between the angle θ and the angle E can be determined by setting the thickness of the non-magnetic thin film and the saturation magnetic flux density of the magnetic layer within a predetermined range. It was possible to set it as the invention range.

Claims (7)

[Claims] 1. A magnetic layer is provided on a substrate, and the magnetic layer comprises:
It has two or more layers of ferromagnetic metal thin films composed of columnar crystal grains formed by the oblique deposition method and a non-magnetic thin film existing between adjacent ferromagnetic metal thin films, and the saturation magnetic flux density Bs of the magnetic layer is 2000-4000 G
The thickness of the non-magnetic thin film is 0.15 to 0.50 times the average value of the thickness of the ferromagnetic metal thin film, and the average growth direction of the columnar crystal grains of all the ferromagnetic metal thin films is almost the same. And the average value of the angle between the growth direction of the columnar crystal grains of each ferromagnetic metal thin film and the main surface of the substrate is θ (where 0 <θ <90 °), and the direction of the easy axis of magnetization of the magnetic layer The angle formed by the main surface of the substrate is E (where 0 <E <90
Magnetic recording medium, wherein E-θ> 0 °. 2. The average value of the thickness of the ferromagnetic metal thin film is 1
The magnetic recording medium according to claim 1, which has a current density of 200 A or less. 3. The magnetic recording medium according to claim 1, wherein the nonmagnetic thin film has a thickness of 100 A or more. 4. The magnetic recording medium according to claim 1, wherein the non-magnetic thin film is mainly composed of an oxide of an element contained in the ferromagnetic metal thin film. 5. The magnetic recording medium according to claim 1, wherein the ferromagnetic metal thin film contains Co as a main component. 6. The ratio of the coercive force (Hc ⊥) in the perpendicular direction of the magnetic layer to the coercive force (Hc //) in the in-plane direction of the magnetic layer is (Hc ⊥) / (Hc //)≧1.1. Item 7. A magnetic recording medium according to any one of items 1 to 5. 7. A residual magnetic flux density (Br
7. The magnetic recording medium according to claim 1, wherein the ratio of ⊥) to the residual magnetic flux density in the in-plane direction of the magnetic layer (Br //) is (Br ⊥) / (Br //)≧1.1.