JPH04353621A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the good recording and replay characteristic of the title recording medium by regulating the film thickness of individual rhombic vapor-deposited films, and the residual flux density as well as the coercive force of a magnetic layer. CONSTITUTION:The title recording medium is formed, on a nonmagnetic support body 1, of a first ferromagnetic metal thin film 2 and a second ferromagnetic metal thin film 3 which are provided with rhombic pillar-shaped structures; the rhombic pillar-shaped structures of the first metal thin film 2 and the second metal thin film 3 are formed in mutually opposite directions. In addition, when the film thickness of the first metal thin film 2 is designated as delta1, the film thickness of the second metal thin film 3 is designated as delta2, the coercive force of the whole of a magnetic layer is designated as Hc and the residual flux density of the whole of the magnetic layer is designated as Br, they are set to values which satisfy formulae I to IV. When the film thickness of the individual rhombic vapor-deposited films 2, 3 as well as the residual flux density and the coercive force of the magnetic layer are regulated, the phase characteristic, the optimum recording current, the C/N ratio and the replay output of the title recording medium do not cause any difference between the positive direction and the opposite direction even when the title recording medium is used back and forth, and it is possible to obtain a good recording and replay characteristic in any case.

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 suitable as a so-called non-tracking magnetic tape.

2. Description of the Related Art The helical scan method, in which a head attached to a rotating drum is operated obliquely to the running direction of a magnetic tape, is used in video tape recorders (VTRs).
), is generally used as a recording method for digital audio tape recorders (DAT), and since this helical scan method is suitable for longer operation times, smaller size, and lower cost, it is also used in addition to VTRs and DATs, such as It is also expected to be used as a recording method for business-use digital memo machines that record audio from meetings and the like.

By the way, in a system employing this helical scan method, it is necessary for the head to accurately trace the recording track during reproduction. For this reason, for example, an AFT signal for tracking is recorded for each track along with recorded data, and during playback, the head detects this AFT signal to determine the positional error with respect to the track to be played back, and uses this error signal as a signal. Based on this, a tracking servo circuit controls the head position. Therefore, in a system that adopts such a helical scan method, it is necessary to install a complicated servo mechanism in addition to the recording/reproducing system, making it difficult to make it smaller than the current size. It seems that improvements are needed to make this a digital memo machine for business use, which requires functionality.

[0003]Recently, therefore, a non-tracking method has been proposed as a recording/reproducing method that allows the servo mechanism to be simplified. In this non-tracking method, when reproducing data recorded by the helical scan method, the head is rotated at, for example, twice (or more than twice) the recording speed. This results in
Even without a complicated tracking servo mechanism, it is possible to completely detect the data recorded on the tape without missing any data.

That is, in the above-mentioned non-tracking method, when recording, as in the case of normal helical scan method recording, a rotating head (double azimuth The block track data is recorded diagonally with respect to the running direction of the tape. Then, during reproduction, the rotary head is rotated at, for example, twice the speed of recording. Then, the head traces the recording track so that it overlaps finely, so even if the recorded data overlaps, it will not be detected as missing, and the DRAM
The data is read into a dynamic write/read memory (dynamic random read/write memory), rearranged based on the frame address and block address attached to the data, and restored as complete data.

Therefore, according to such a non-tracking method, since there is no need for the head to precisely trace the track, the conventional tracking servo circuit using AFT signals can be omitted, and the device can be made smaller and lighter. It becomes possible. In addition, in the normal helical scan method used in DAT etc., as mentioned above, the head needs to be placed faithfully to the track, so a highly accurate loading mechanism is essential. The tracking method eliminates the need for such a highly accurate loading mechanism. Therefore, we have created a tape guide shaft inside the tape cassette that has the functions of vertical guides and inclined pins that were conventionally located on the device side, and forms a tape path by simply protruding the rotating drum into the tape cassette without loading the tape. This makes it possible to realize a loading method, which further reduces the size of the device.
It becomes possible to improve the lightness.

By the way, in systems that employ this non-tracking method, since the non-tracking method is suitable for miniaturization and weight reduction, studies and development are proceeding toward ultra-compact recording and reproducing devices. For example, a tape cassette serving as a recording medium is assumed to have a size of about 30 x 21.5 x 5 mm, the size of a postage stamp, and a recording time of about 2 hours. Therefore, the magnetic tape is required to have a high recording density so that good recording and playback can be achieved even when the magnetic tape is made into a cassette of the above size and is recorded and played back at the above recording time. As a recording medium, it has been considered to employ a so-called obliquely evaporated tape, in which a ferromagnetic metal thin film is formed by obliquely evaporating a Co--Ni alloy or the like on a non-magnetic support.

As shown in FIG. 7, this obliquely evaporated tape is made up of a ferromagnetic metal thin film 31 having an orthorhombic columnar structure formed on a non-magnetic support 32, and has a high saturation magnetization,
It has the advantage of having a high coercive force and being able to demonstrate high output from the high wavelength region to the short wavelength region, and is suitable for VTRs and DATs.
It has already been put into practical use as a recording medium for.

However, if the above-mentioned obliquely vapor-deposited tape is used in a non-tracking system, the following problems will occur.

That is, in the vapor-deposited tape, when the head slides in the positive direction (direction of arrow a in the figure) with respect to the growth direction of the orthorhombic columnar structure of the ferromagnetic metal thin film during recording and reproduction, the above-mentioned However, when sliding in the direction opposite to the growth direction of the orthorhombic columnar structure (direction of arrow b in the figure), the optimum recording current, phase characteristics, CN ratio, and output This has the drawback that the properties and other characteristics are inferior to those when sliding in the forward direction, and sufficient recording and reproducing characteristics cannot be obtained. For this reason, in systems where the head slides only in one direction with respect to the growth direction of the ferromagnetic metal thin film, such as VTRs and DATs, good recording and reproducing can be achieved. For example, in a reciprocating system where the head slides in both forward and reverse directions, such as a reciprocating system in which the magnetic tape is divided into upper and lower sections in the width direction and recorded and played back individually, when the head slides in the opposite direction, recording and playback cannot be performed. A problem arises in that the characteristics deteriorate.

In a system using the non-tracking method, the objective is to downsize the cassette and secure a recording time, so the reciprocating specification is adopted in order to secure a recording time. Therefore, the above-mentioned problems of the vapor-deposited tape greatly affect its recording and reproducing performance.

[0011] Therefore, as an obliquely evaporated tape that solves these problems, an obliquely evaporated tape has been proposed in which the magnetic layer is composed of two obliquely evaporated films grown in different directions. In this two-layer obliquely vapor-deposited tape, the sliding direction of the head relative to the tape may be the same or different from the growth direction of the ferromagnetic metal thin film on the side that the head contacts (hereinafter referred to as , regarding the sliding direction of the head,
The case where the sliding direction is the same as the growth direction of the orthorhombic columnar structure of the ferromagnetic metal thin film on the side that contacts the head is called a positive direction, and the case where it is in a different direction is called a reverse direction. ) Since it exhibits similar phase characteristics and optimal recording current, it is attracting attention as a magnetic recording medium for non-tracking.

0012

[Problem to be solved by the invention] However, the above 2
For the layered obliquely vapor-deposited tape, differences in phase characteristics and optimum recording current due to head sliding direction are eliminated, but other characteristics, such as CN ratio and reproduction output, are affected by head sliding. It exhibits different characteristics depending on whether the direction is forward or reverse, and cannot be said to be fully satisfactory as a reciprocating magnetic tape.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and provides good recording and reproducing characteristics regardless of whether the head slides in the forward or reverse direction. It is an object of the present invention to provide a magnetic recording medium suitable as a magnetic tape for a non-tracking system.

[0014]

[Means for solving the problem] When a conventional two-layer obliquely vapor-deposited tape is used back and forth, there is almost no difference in phase characteristics and optimum recording current depending on the sliding direction of the head, but there is a difference in CN ratio and playback output. The magnetic tape differs depending on whether the head slides in the forward direction or in the reverse direction, and cannot be said to be sufficient as a magnetic tape for a non-tracking system that requires reciprocating use. As a result of repeated studies by the inventors on the difference in CN ratio and output characteristics depending on the sliding direction of this head, we found that the difference in characteristics depending on the sliding direction of this head is due to the thickness of each ferromagnetic metal thin film and the overall magnetic layer. We have found that this problem can be solved by adjusting the coercive force and residual magnetic flux density.

The magnetic recording medium of the present invention has been proposed based on such knowledge, and comprises a first ferromagnetic metal thin film having an orthorhombic columnar structure and a second ferromagnetic metal thin film on a nonmagnetic support. A magnetic layer is formed by sequentially laminating metal thin films,
The growth direction of the orthorhombic columnar structure of the first ferromagnetic metal thin film and the growth direction of the orthorhombic columnar structure of the second ferromagnetic metal thin film are opposite to each other, and the first ferromagnetic metal thin film 1600 Å≦δ1 + δ2 ≦2000 Å1/ 3≦δ2
/δ1≦2/3 Hc≦1200Oe Hc×Br×(δ1 +δ2)≧50Oe・cm・G
It is characterized by:

The magnetic recording medium of the present invention, for example, as shown in FIG. A second ferromagnetic metal thin film 3 whose growth direction of an orthorhombic columnar structure is opposite to that of the first ferromagnetic metal thin film is laminated.

The first ferromagnetic metal thin film 2 and the second ferromagnetic metal thin film 3 are formed by, for example, an oblique evaporation method.

First, in order to form the first ferromagnetic metal thin film 2 by the oblique evaporation method, as shown in FIG. 41, and the winding roll 50
Leave it so that it can be wound up. Then, while moving the non-magnetic support 1 in the r direction in the figure in accordance with the rotation of the drum 41, the metal material 43 filled in the crucible 44 to become a ferromagnetic metal thin film is evaporated, and the metal material 4
Vapor deposition is carried out while the vapor flow Y from 3 is incident on the nonmagnetic support 1 at a certain incident angle θ with respect to the normal direction X to the surface of the nonmagnetic support 1. At this time, a mask 45 is placed near the drum 41.
is arranged to regulate the incident angle θ of the vapor flow Y. As a result, vapor deposition on the non-magnetic support 1 is performed in a region up to the point where the surface of the non-magnetic support 1 is shielded by the mask 45, and the incident angle θ of the vapor flow Y is As the body 1 moves, the angle gradually changes from a high angle to a low angle, and reaches a minimum value at the position where the mask 45 is placed. The range of change of the incident angle θ of this vapor flow Y is 9
It is preferable to set it as 0-30 degrees. Also, mask 45
An O2 gas inlet is provided at the end of the support, and O2 gas is supplied to the surface of the vapor nonmagnetic support 1 from this O2 gas inlet. The supply of O2 gas improves the durability of the magnetic layer against oxidation, and at the same time, by adjusting the amount of O2 gas supplied at this time, the magnetic properties such as the coercive force and residual magnetic flux density of the ferromagnetic metal thin film are controlled. be able to.

After forming the first ferromagnetic metal thin film 2 in this manner, a second ferromagnetic metal thin film 3 is formed on the first ferromagnetic metal thin film 2 by an oblique vapor deposition method. . At this time, in order to make the growth direction of the orthorhombic columnar structure opposite to the growth direction of the first ferromagnetic metal thin film 2, the non-magnetic support on which the first ferromagnetic metal thin film 2 is formed is The take-up roll on which No. 1 has been wound is then placed on the unwinding roll side. Then, the non-magnetic support 1 is placed on a drum 41.
It is moved in the r direction across the outer circumferential surface 41a, and vapor deposition is performed using the same method as described above. As a result, the non-magnetic support 1 travels in the opposite direction to the drum when the first ferromagnetic metal thin film 2 is formed. The second growth direction is opposite to that of the case.
A ferromagnetic metal thin film 3 of 3 is formed.

The metal materials constituting the first ferromagnetic metal thin film 2 and the second ferromagnetic metal thin film 3 are as follows:
There is no particular limitation, and for example, Co alone or a combination of two or more of Co, Ni, Ta, Cr, Pt, etc. can be used. Examples of this combination include Co and Ni, Co and Pt, Co and Ta,
Examples include Co and Cr. In addition, the above-mentioned non-magnetic support 1
Any of those normally used in this type of magnetic recording medium can be used.

Furthermore, the magnetic recording medium may be provided with an undercoat film, a back coat layer, or a top coat layer on the non-magnetic support, if necessary. In this case, the materials for the undercoat film, backcoat layer, and topcoat layer are not particularly limited as long as they are normally used in this type of magnetic recording medium.

[0022] A magnetic recording medium having such a two-layered obliquely deposited film as a magnetic layer can be used reciprocatingly in the forward direction (direction of arrow A in FIG. 1) and in the reverse direction (direction of arrow B in FIG. 1). There is no difference in phase characteristics or optimum recording current, making it more suitable for reciprocating specifications than single-layer magnetic recording media. However, in order to make the above-mentioned obliquely vapor-deposited film equally good in terms of CN ratio and reproduction output characteristics in both the forward and reverse directions, it is necessary to The film thickness δ2 of the magnetic metal thin film 3, the coercive force Hc of the entire magnetic layer, and the residual magnetic flux density B
r needs to be adjusted.

Therefore, in the magnetic recording medium of the present invention, when a reciprocating specification is performed using a non-tracking method,
In order to exhibit a high CN ratio and high reproduction output in both forward and reverse directions and obtain a good reproduction signal (a reproduction signal with an error rate of 1×10-2 or less), δ1, δ2,
It is assumed that Hc and Br are set so as to satisfy the following relationship. 1600Å≦δ1 +δ2 ≦2000Å1/3≦δ2
/δ1≦2/3 Hc≦1200Oe Hc×Br×(δ1 +δ2)≧50Oe・cm・G

[0024] Here, δ1 + δ2 is 1600 to 20
If it is not within the range of 00 Å, the error rate will be high and a good reproduced signal will not be obtained regardless of whether the head is sliding in the forward or reverse direction. Also, δ2
If /δ1 is less than 1/3, the error rate will be high when recording and reproducing by sliding the head in the forward direction, and if δ2 /δ1 is set to more than 2/3, the error rate will be high. , the error rate increases when the head slides in the A direction, and in either case, it is insufficient as a reciprocating magnetic tape.

On the other hand, Hc×Br×(δ1 +δ2) is set from the viewpoint of obtaining sufficient reproduction output by the non-tracking method. That is, it is generally known that the reproduction output of a ring head is approximately proportional to the in-plane coercive force, residual magnetic flux density, and thickness of the magnetic layer of the magnetic recording medium. In the non-tracking method, +3.5d is required to keep the error rate below 1x10-2.
It has been found through experiments that a reproduction output of B or more is required. To obtain a playback output of +3.5dB or more,
Hc x Br x (δ1 + δ2) is 50 Oe・cm・G
It is necessary that Hc×Br×(δ1 +
If δ2) is less than 50 Oe·cm·G, the reproduction output will be insufficient and the error rate will increase.

The coercive force Hc is set in consideration of the characteristics and current consumption of the head used in the non-tracking system. That is, in a non-tracking system, the recording current is usually set to 20 mA or less. Therefore, the magnetic recording medium must be capable of recording with a recording current of 20 mA or less. For this purpose, the coercive force Hc needs to be 1200 Oe or less, and if the coercive force Hc exceeds 1200 Oe, sufficient recording will not be possible, resulting in a reduction in reproduction output.

[0027]

[Function] What is the first ferromagnetic metal thin film made of metal particles having an orthorhombic columnar structure on a non-magnetic support, and the metal particles of the first ferromagnetic metal thin film having an orthorhombic columnar structure with the long axis direction? In a magnetic recording medium in which a second ferromagnetic metal thin film made of metal particles in opposite directions is laminated, the thickness of the first ferromagnetic metal thin film, the thickness of the second ferromagnetic metal thin film, and the magnetic layer By controlling the overall coercive force and residual magnetic flux density, there is almost no difference in characteristics depending on the sliding direction of the head when using the non-tracking method back and forth, and a high CN ratio and high playback output can be achieved in both forward and reverse directions. .

[0028]

EXAMPLE A preferred example of the present invention will be explained based on experimental results.

Experimental Example 1 This experimental example is an example in which the film thickness δ1 + δ2 of the magnetic layer was investigated.

[0030] In order to produce the obliquely evaporated tape, first, an undercoat is applied to the non-magnetic support, and then Co80-Ni20
Using the alloy as a deposition source, vapor deposition is performed twice by changing the traveling direction of the non-magnetic support relative to the drum to form a first ferromagnetic metal thin film,
A second ferromagnetic metal thin film was formed. Next, a back coat layer and a top coat layer consisting of a lubricant are formed,
It was cut to a specified width and assembled into a cassette.

[0031] The vapor deposition was carried out by setting the variation range of the incident angle of the vapor flow to 90 to 45° and the O2 supply rate to 200 cc/min. At this time, the film thicknesses δ1 and δ2 of the ferromagnetic metal thin films were adjusted by controlling the beam current supplied to the crucible to keep the amount of vapor flow constant and changing the moving speed of the tape. In this example, the thickness of the deposited film was determined by the tape moving speed of 14 m.
/min, it was 2000 Å.

By such a method, various obliquely evaporated tapes were produced by varying the film thickness δ1 + δ2 within a range where δ1 :δ2 was 1:0.5. Then, recording and reproduction were performed on the various obliquely vapor-deposited tapes produced in both forward and reverse directions, and the error rate was measured.

Table 1 shows the film thickness δ1 of the first ferromagnetic metal thin film and the film thickness δ2 of the second ferromagnetic metal thin film of each obliquely evaporated tape.
, the thickness δ1+δ2 of the entire magnetic layer, the coercive force Hc, the residual magnetic flux density Br, and the error rate during reproduction. Further, FIG. 3 shows the relationship between the thickness δ1 +δ2 of the magnetic layer and the error rate.

[Table 1]

As can be seen from FIG. 3, in the case of the obliquely evaporated tape, the change in error rate due to the thickness of the magnetic layer has a minimum value regardless of whether the head slides in the forward or reverse direction. It is represented by a nearly hyperbola. Here, in a non-tracking system, in order to obtain a good reproduction signal, it is necessary that the error rate is 1 x 10-2 or less, and the magnetic The thickness of the layer is 1600-2000 Å. Therefore, this indicates that in order to obtain an obliquely evaporated tape that can be used as a non-tracking magnetic tape, it is preferable to set the thickness δ1 +δ2 of the magnetic layer to 1600 to 2000 Å.

Experimental Example 2 This experimental example is an example in which the film thickness ratio δ2/δ1 was investigated. Using the same method as in Experimental Example 1, the thickness of the magnetic layer δ1 +δ
Various obliquely evaporated tapes were produced by changing δ2/δ1 within a range where 2 was 1800 Å. Then, recording and reproduction were performed in both forward and reverse directions for the various obliquely vapor-deposited tapes produced, and the error rate was measured.

Table 2 shows the film thickness δ1 of the first ferromagnetic metal thin film and the film thickness δ2 of the second ferromagnetic metal thin film of each obliquely evaporated tape.
, film thickness ratio δ2/δ1, coercive force Hc, residual magnetic flux density Br, and error rate during reproduction. Further, FIG. 4 shows the relationship between the film thickness δ1 of the first ferromagnetic metal thin film and the error rate.

[Table 2]

As can be seen from FIG. 4, in the case of the obliquely evaporated tape, when the sliding direction of the head is in the positive direction, the error rate increases as the film thickness δ1 of the first ferromagnetic metal thin film increases. On the other hand, in the opposite direction, the smaller the film thickness δ1, the higher the error rate, and the error rate tends to decrease as the film thickness δ1 increases. Here, the film thickness δ1 at which the error rate is 1×10 −2 or less in both forward and reverse directions is 1080 to 1350 Å. Therefore, in order to obtain an orthogonal vapor deposition tape that can be applied as a magnetic tape for non-tracking systems,
It was shown that the film thickness ratio δ2/δ1 is preferably set to 1/3 or more and 2/3 or less.

Experimental Example 3 In this experimental example, the energy product Hc×Br×(δ1 +δ2
) and coercive force Hc. In addition to Co80-Ni20, Co100 is used as a deposition source during vapor deposition.
by changing the O2 supply amount to increase the residual magnetic flux density Br.
Various obliquely evaporated tapes were produced in the same manner as in Example 1, except that the coercive force Hc was adjusted. Then, recording and reproduction were performed in both forward and reverse directions on the various obliquely vapor-deposited tapes produced, and the reproduction output and optimum recording current were measured.

Table 3 shows O2 during vapor deposition of each oblique vapor deposition tape.
The supply amount, coercive force Hc, residual magnetic flux density Br, energy product Hc×Br×(δ1 +δ2), optimum recording current, and reproduction output are shown. In addition, Fig. 5 shows the energy product Hc×Br×
The relationship between (δ1 +δ2) and reproduction output is shown in FIG. 6, and the relationship between coercive force Hc and optimum recording current is shown in FIG. Note that the reproduction output shown in FIG. 5 is a ratio with that of a metal-coated magnetic tape, and the optimum recording current shown in FIG. 6 is expressed in dB with 20 mA as a reference.

[Table 3] As can be seen from FIG. 5, in the case of the obliquely evaporated tape, the reproduction output increases as the energy product increases in both the forward and reverse directions. In the non-tracking method, in order to suppress the error rate to 1 x 10-2 or less, the reproduction output must be +3.5 dB or more, and the reproduction output must be 3.5 dB or more for both forward and reverse playback. The energy product was 50 Oe or more. therefore,
In order to obtain an obliquely evaporated tape that can be used as a magnetic tape for non-tracking systems, the coercive force Hc and residual magnetic flux density Br must be Hc×Br×(δ1 +δ2)≧50.
It was shown that it is preferable to set it so that Oe.

Furthermore, as can be seen from FIG. 6, the recording current used in the non-tracking system is 2.
The optimum recording current is 0 mA or less when the coercive force Hc is 1.
This is the case of 200 Oe. Therefore, from this,
To obtain an obliquely evaporated tape that can be used as a magnetic tape for non-tracking systems, the coercive force Hc must be 1200 Oe.
It has been shown that the following settings are suitable.

The measuring equipment used to measure the electromagnetic conversion characteristics and magnetic characteristics in each experimental example is shown below. Magnetic properties (coercive force, residual magnetic flux density) Measuring device: Vibrating sample magnetometer Electromagnetic conversion characteristics (optimal recording current, playback output, error rate) Measuring device: Sony Corporation, product name NT-1
(Modified product) Head specifications
Type/MIG (metal in gap) head
Material: Single crystal ferrite (MnZn)
(Gap part is Sendust) Gap length: 0.22μm Recording wavelength
0.67μm Sampling frequency 32kHz Quantization bit number
12bit broken line

[0042]

Effects of the Invention As is clear from the above description, the magnetic recording medium of the present invention has two obliquely deposited films having different major axis directions as magnetic layers. Since the film thickness, residual magnetic flux density and coercive force of the magnetic layer are regulated, the phase characteristics, optimum recording current, C/N ratio, and playback output will vary in the forward and reverse directions even when used back and forth in a non-tracking method. There is no difference, and good recording and reproducing characteristics can be obtained in either case. therefore,
According to the present invention, it is possible to realize a magnetic tape having sufficient characteristics as a magnetic tape for a non-tracking system, and it is possible to improve the practicality and performance of a non-tracking system.

[0043]

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a configuration example of a magnetic recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view of a main part of a vapor deposition apparatus used for vapor deposition of a ferromagnetic metal thin film.

FIG. 3 is a characteristic diagram showing the relationship between the thickness δ1 +δ2 of the magnetic layer and the error rate.

FIG. 4 is a characteristic diagram showing the relationship between the film thickness ratio δ2/δ1 and the error rate.

[Figure 5] Energy product Hc x Br x (δ1 + δ2)
FIG. 3 is a characteristic diagram showing the relationship between the output power and the reproduction output.

FIG. 6 is a characteristic diagram showing the relationship between coercive force Hc and optimum recording current.

FIG. 7 is a schematic cross-sectional view showing the structure of a conventional oblique vapor deposition tape.

[Explanation of symbols]

1...Nonmagnetic support 2...First ferromagnetic metal thin film 3...Second ferromagnetic metal thin film

Claims (1)

[Claims] 1. A magnetic layer is formed in which a first ferromagnetic metal thin film and a second ferromagnetic metal thin film having an orthorhombic columnar structure are sequentially laminated on a non-magnetic support, The growth direction of the orthorhombic columnar structure of the magnetic metal thin film and the growth direction of the orthorhombic columnar structure of the second ferromagnetic metal thin film are opposite to each other, and the film thickness of the first ferromagnetic metal thin film is set to δ1.
, the thickness of the second ferromagnetic metal thin film is δ2, the coercive force of the entire magnetic layer is Hc, and the residual magnetic flux density of the entire magnetic layer is Br.
When, 1600Å≦δ1 +δ2 ≦2000Å1/3≦δ2
/δ1≦2/3 Hc≦1200Oe Hc×Br×(δ1 +δ2)≧50Oe・cm・G
A magnetic recording medium characterized by