JPH01317221A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To execute recording and reproduction at a high density and high S/N by specifying the relation between the coercive force in the direction perpendicular to the film plane of the medium and the coercive force in the intra-film surface direction and specifying the relation between the medium noise value at the time of recording at a specific recording density and the medium noise values respectively at the time of DC erasing and AC erasing. CONSTITUTION:The relation between the coercive force Hcrt. angle in the direction perpendic ular to the film plane of the medium and the coercive force Hc in the intra-surface direction is specified to 1/2Hcrt. angle<=Hcrt. angle and the film thickness delta of the recording layer is specified to delta>0.1lambda with respect to a recording wavelength lambda. The relation between the medium noise ND50 at the time of the signal recording at the recording density D50 at which the reproduced output is reduced to half the low-density output and the DC erasing noise NDC and AC erasing noise NAC is specified to NDC<=ND50<NAC. The magnetization, therefore, has a perpendicular component strongly with an increase in the recording density and the zigzag magnetization transition does not take place any longer. The medium noises decrease and the recording density of D50 enters the noise decrease region past the peak of the medium noises. The recording and reproduc tion of the high S/N in the high density region are executed in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a recording medium used in a magnetic disk device, a magnetic tape device, etc., and particularly to a recording medium suitable for high-density, high-S/N recording. .

[Conventional technology]

In order to achieve high-density recording in the conventional in-plane recording method that utilizes residual magnetization in the in-plane longitudinal direction, for example, it is necessary to
982) As shown on pages 260 to 267,
A continuous thin film medium of a Co--Nj alloy is used as a recording medium, and the coercive force is increased while the recording magnetic layer is made thinner.

On the other hand, a method suitable for increasing the density is Co/Cr, in which the axis of easy magnetization is strongly oriented perpendicular to the film surface of the medium.
A perpendicular recording method using an alloy medium based on IE Transactions on Magnetics, MNG 13° Number 5 (1977) 127
Pages 2 to 1274 (:rEEE 1'rans, on
Magn, Vo], MAG-13, Nn5 (+977
) P P 1.272-1274).

[Problem to be solved by the invention] In the above Co-Ni-based in-plane continuous thin film medium, as shown in curve 11 in Fig. 4 and curve 21 in Fig. 2, the reproduction output at low density is high. However, as the recording density increases, the medium noise increases and reaches its maximum value near the recording density (this recording density is generally referred to as Dδ0) where the reproduced output is halved compared to the low-density output.

This is due to the reasons described below. In an in-plane continuous thin film medium, the magnetization does not reverse at minus-like positions across the width of the recorded track, creating a zigzag-like boundary. In this magnetization transition region, the direction of magnetization is randomly oriented and becomes a source of media noise. When the recording density is increased, the ratio occupied by the zigzag magnetization transition region increases, resulting in an increase in noise. When the recording density is further increased, adjacent magnetization transition regions interfere with each other, resulting in a decrease in reproduction output, and since the magnetization transition regions occupy the majority of the recording, the noise reaches its maximum value. This state is a state in which most of the region has random magnetization directions, so it is almost equal to AC erase noise.

Regarding the above development, please refer to IEE1-Transactions on Magnetics, MNG21. Number 5 (1985)] 350 pages to 1
355 pages (IEEE 1'rans, on Magn.

vol, MAG-21, Nn5 (1985) P
P l 350-1355), IE Transactions on Magnetics, M.
Nie G22. Number 5 (1986) pp. 895-897 (IEEE Trans, on Magn
, vol, , MAG-22°Nα5 (1986) PP8
95-897) and others.

By the way, when performing magnetic recording, the maximum recording density of the signal is
Generally, it is about D30. Therefore, due to the above noise characteristics, there is a problem that the S/N of the reproduced signal becomes small at a recording density near D50.

On the other hand, when a vertical medium such as Co-Cr is used, the medium noise is constant regardless of the signal recording density, as shown by curve 12 in Figure 1 and curve 22 in Figure 2, and l'')50 is also high. , suitable for high-density recording.

This noise characteristic is due to the fact that a perpendicular medium does not have a zigzag magnetization transition region unlike an in-plane continuous thin film medium, and the magnetization transition does not become a noise source. Co-C as above
Regarding the noise characteristics of P-perpendicular media, IE Transactions on Magnetics,
M.N.G.21, Number 5 (1985) 13
Pages 50 to 1355 N (IEEE Trans, on
Magn, vol, HAG-21°Nα5 (1985
) P P 1.350-1355). However, as shown in curve 12 in Figure 1, the playback output is small, so the total S
There is a problem that /N becomes small.

The purpose of the present invention is to improve the S/N ratio between an in-plane continuous thin film medium and a perpendicular medium.
Based on the above-mentioned problems regarding Dr+o, the reproduction output at D5o is higher than the in-plane continuous thin film medium, and the recording and reproduction density characteristic (curve 13 in Figure 4) is higher than that of the perpendicular medium. By achieving a noise characteristic (curve 23 in Figure 2) in which the medium noise passes its peak and enters a low-noise region at a recording density of An object of the present invention is to provide a recording medium capable of recording and reproducing data of /N.

[Means to solve the problem]

The above purpose is to improve the coercive force HC⊥ in the direction perpendicular to the medium film surface and the coercive force Hc in the in-plane direction in a continuous thin film medium.
The relationship tt is -He≦HC//≦HC⊥, and the thickness δ of the recording layer is set to the recording wavelength λ when δ>0. ]λ, and the relationship between the medium noise ND50 during signal recording of D5o and the DC cancellation noise NDC1 and the AC cancellation noise NAC is N
This is achieved by setting oc≦N o5o < N AC.

[Effect]

Vertical coercive force HC⊥ and in-plane coercive force Hc //
A medium in which the relationship is He=Hc is an isotropic medium, which is represented by the boundaries of regions 51 and 53 in FIG. When the coercive force HC // in the in-plane direction becomes larger than this, magnetization becomes easy in the plane and becomes an in-plane medium (region 51 in FIG. 5).

Conversely, as the coercive force in the perpendicular direction increases, it becomes closer to a perpendicular medium, but a highly oriented perpendicular medium that provides excellent high-density characteristics as a perpendicular medium is generally in the region of HC⊥) 2 Hctt (region 52 in Figure 5). be.

The relationship between Ha and HC// is -HC⊥≦Hc ti≦H
When C⊥, as shown in region 53 in FIG. 5, the medium is intermediate between a longitudinal medium and a perpendicular medium. That is, the recorded magnetization includes a perpendicular component and an in-plane component, the extent of which depends on the magnitude of the demagnetizing field of both components.

In other words, during low-density signal recording, since the demagnetizing field in the perpendicular direction is large, the magnetization direction tends to be in-plane.

On the other hand, during high-density signal recording, the in-plane demagnetizing field becomes stronger.
In addition, since the perpendicular demagnetizing field weakens, the magnetization becomes oriented in the direction of the perpendicular force. This phenomenon appears more prominently as the medium film thickness δ increases due to the magnitude of the demagnetizing field.

Therefore, since the above medium has in-plane magnetization during low-density signal recording, a zigzag-like magnetization transition region occurs as in the in-plane continuous thin film medium, and as the recording density increases, the medium noise increases and the AC erase noise NAC Get closer. When the density is further increased, the magnetization has a strong perpendicular component for the reason mentioned above, and zigzag magnetization transitions no longer occur, so the medium noise decreases, and the recording density of D50 passes the peak of the medium noise, and the noise This will be a declining area. Therefore, the relationship between the medium noise ND50 during signal recording of D5o, the DC erasure noise Noc, and the AC erasure noise NAC is 1'Joc≦ND50≦NAC.

〔Example〕

Embodiments of the magnetic recording medium according to the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing a cross-sectional structure of an embodiment of a magnetic recording medium according to the present invention. A Cr underlayer 33. is formed on the nonmagnetic substrate 34 by vacuum evaporation. Co—Cr recording magnetic layer 32. The nonmagnetic surface protective layer 31 was laminated in this order. The film thickness of the Cr underlayer is 300 mm.

The film thickness δ of the -Cr recording magnetic layer is 0.2 μm, and the coercive force is 4000e both in the plane and in the die direction. Here, the Cr underlayer 33 has the function of making it easier to orient the axis of easy magnetization of the Co--Cr layer in the in-plane direction. Regarding the base film material, Cr
The present invention is not limited to , but any material having a similar function may be used. Materials that can achieve this effect include Cr, C
u, V, Mo.

There are W and alloys containing these as main ingredients. Further, the manufacturing method may be a sputtering method. Furthermore, as a method for making the direction of easy magnetization of the Co-Cr layer more in-plane, G
There is also a method of introducing a gas such as Oz as an impurity during vapor deposition or sputtering of the o-Cr layer.

As a result of recording and reproducing on the medium described above at a relative speed of 2.5 m/s using a ring head with 1-rack width of 45 μm and 9 windings of 50 turns, Dr+o was 45 KFCT2 The medium measured in frequency bands 4 and 5 MHz The noise values are: DC erasure noise NDc = 3.5μV rms, AC erasure noise NAc = 5.5μVrms, medium noise No. 5o when recording a signal with a recording density of D5o = 4, 2μV r
It was ms.

FIG. 1 is a diagram showing the recording density dependence of medium noise during signal recording on the medium. In the low density region, the medium noise value increased as the recording density increased, reaching a maximum value at a recording density of 20KFCT, and the value was comparable to NAC. If the recording density is further increased, the medium noise will conversely decrease. The medium noise value at the recording density of D50 is -2.3 dr3 with respect to the maximum value.

Generally, the maximum recording density used in a magnetic recording device is about D50, so when the medium shown in this embodiment is used, recording and reproduction can be performed in an area with low noise.

In FIG. 1, the noise begins to decrease due to the contribution of the perpendicular component of magnetization, the strength of which is determined by the demagnetizing field coefficient. The demagnetizing field coefficient is determined by the ratio λ/δ of the recording wavelength λ and the medium film thickness δ. In this example, the region where the noise starts to decrease from FIG. 1 is λ/8<10. Based on this result, when the recording wavelength λ to be used is determined, in order to obtain the above effect, the medium film thickness δ needs to be δ>0.1λ. For example, 50Kl・CI (λ=1μ
m), the medium film thickness is δ>0.1 μm. On the other hand, the upper limit of the film thickness is determined by the recording ability of the head.

FIG. 5 shows the relationship between various types of continuous thin film media with different relationships between the perpendicular coercive force He and the in-plane coercive force Hc//, and the types of media.

The plot marked Δ in the figure is a continuous thin film medium of the Go-Ni system, and the in-plane medium region 51 where HCJL < Hcti
belongs to The open plot shows a medium in which Co-Cr)l is deposited directly on a non-magnetic substrate or via a Ge or Ti underlayer, and both are Hcl)2HC//
It belongs to the vertical media area 52 of . The mark O in the figure indicates the case where a Go--Cr layer was laminated on a Cr underlayer by the method of the above embodiment, and the noise characteristic was shown as curve 23 in FIG. 2. These areas belong to an intermediate area between the vertical medium area 52 and the in-plane medium area 51 in terms of the relationship between Hcl and HC//. In other words, the relationship between Hcl and Hcti is -HC≦Hctt≦
It is denoted by HC⊥.

〔Effect of the invention〕

As shown above, according to the present invention, the higher the density, the lower the medium noise.
N recording/reproduction can be realized, which is effective in realizing a high-density magnetic recording device.

[Brief explanation of the drawing]

FIG. 1 is a recording density dependence characteristic of noise during signal recording of a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is a recording density dependence characteristic of medium noise during signal recording of the same medium, and FIG. 3 is a graph of the present invention. FIG. 4 is a cross-sectional view of the magnetic recording medium of the example of Co-N
Figure 5 shows the recording density characteristics of i-based in-plane continuous thin film media and Co--Cr perpendicular media. FIG. 3 is an explanatory diagram showing magnetic properties. 11... Recording density characteristics of Co-Ni-based in-plane continuous thin film medium, 12... Recording density characteristics of Co-Cr vertical medium,
13... Target recording density characteristics, 21... co -N
Noise characteristics of i-based in-plane continuous thin film media, 22...G o
-Noise characteristics of Cr perpendicular medium, 23...Target noise characteristics, 31...Nonmagnetic surface protective layer, 32...Co
-Cr recording magnetic layer, 33...Cr underlayer, 34...
Non-magnetic substrate, 51... In-plane medium region, 52... Perpendicular medium region, 53... Intermediate region.

Claims (1)

[Claims] 1. In a continuous thin film magnetic recording medium, the relationship between the coercive force H_C_⊥ in the direction perpendicular to the medium film surface and the coercive force H_C_■ in the in-plane direction is 1/2H_C_⊥≦H_C_ ■≦H_C_⊥, the recording magnetic layer thickness δ>0.1λ for the recording wavelength λ, and the medium noise value when recording a signal at a recording density (D_5_0) where the reproduction output is half that of the low-density output. N_D_5_0, medium noise value N_D_C during DC clearing, and medium noise value N_A_ during AC clearing.
A magnetic recording medium characterized in that the relationship of C is N_D_C≦N_D_5_0<N_A_C.