JPH10283624A - Perpendicular magnetic recording medium and memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent magnetic recording medium which does not give rise to the deterioration in signal even in an external magnetic field by forming the film thickness of a soft magnetic layer which is an intermediate layer of the perpendicular magnetic recording medium having a three-layered structure to a specific value or above. SOLUTION: A hard magnetic layer 2, the soft magnetic layer 3 formed of CoZrNi and a perpendicular layer 4 are successively laminated on a substrate 1 and a protective layer 5 is formed on this perpendicular layer 4. The hard magnetic layer 2 has function to fix the magnetization of the soft magnetic layer 3 weak to external magnetic fields and eventually to stabilize the magnetization of the perpendicular layer 4 and is formed of, for example, CoSm, etc. The soft magnetic layer 3 is so formed as to have a film thickness of >=600 nm. The perpendicular magnetic recording medium formed in such a manner is built into a HDD, etc., by which the magnetic recording medium having a high density and excellent reliability is obtd. If the film thickness is below 600 nm, the signal stability to the external magnetic fields is insufficient, degaussing occurs and the embodiment of the high reliability when the medium is built into external memory device is not possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a perpendicular magnetic recording medium having a three-layer structure and a storage device using the same.

[0002]

2. Description of the Related Art In recent years, an HDD (Hard Disk Drive) has been widely used as an external storage device of a computer. The recording disk incorporated in this HDD is mainly an in-plane magnetic recording medium. On the other hand, the perpendicular magnetic recording system using a perpendicular magnetic recording medium can achieve higher densities than the longitudinal magnetic recording system using a longitudinal magnetic recording medium, and it supports this idea. More data has been published than before. Conventionally, this perpendicular magnetic recording medium has a two-layer structure in which an in-plane soft magnetic layer (hereinafter, referred to as a soft magnetic layer) and a perpendicular magnetic recording layer (hereinafter, referred to as a perpendicular layer) are laminated in this order on a substrate.

However, such a two-layered perpendicular magnetic recording system has the following effects: (1) the high density of the in-plane magnetic recording system has been remarkably advanced; It has not been easily realized because of its large size and (3) its susceptibility to external magnetic fields (William Cain et al.,
IEEE TRANSACTIONS ON MAGN
ETICS, VOL. 32, NO. 1, JUNUARY
1996).

However, recently, it has been found that a signal written on an in-plane magnetic recording medium is easily affected by heat, and there is a concern that high density will be stopped in the near future. As a substitute for this, practical use of the perpendicular magnetic recording system has been expected again.
In putting the perpendicular magnetic recording system into practical use, the above (2)
The problem described above has been improved to an area where there is no hindrance due to the recent low flying height of the head. The problem (3) has been improved to a considerable extent by the three-layered perpendicular magnetic recording medium already proposed by the present inventors (JP-A-7-129).
946). This perpendicular magnetic recording medium having a three-layer structure is obtained by providing an in-plane hard magnetic layer (hereinafter, referred to as a hard magnetic layer) between the in-plane soft magnetic layer and the substrate of the above-described two-layer structure medium. The hard magnetic layer has a function of fixing the magnetization of the soft magnetic layer that is weak to an external magnetic field, and thereby stabilizing the magnetization of the perpendicular layer.

[0005]

In the above-described perpendicular magnetic recording medium having a three-layer structure, a recording signal with respect to an external magnetic field (approximately 0.3 [Oe]) equivalent to general geomagnetism is very stable. . However, it has recently been found that signal demagnetization occurs in an external magnetic field of about several tens [Oe]. Therefore, it is desired to develop a perpendicular magnetic recording medium having excellent recording signal stability even in a magnetic field of several tens [Oe] and a highly reliable external storage device incorporating such a magnetic recording medium. I have.

[0006]

The present inventors have focused on the relationship between the thickness of the soft magnetic layer, which is the intermediate layer of a perpendicular magnetic recording medium having a three-layer structure, and the stability of signals with respect to an external magnetic field. The present invention was completed by finding the lower limit of the thickness of the in-plane soft magnetic layer capable of achieving the above object. That is, according to the present invention, there is provided a perpendicular magnetic recording medium in which a hard magnetic layer, a soft magnetic layer, and a perpendicular layer are sequentially laminated on a substrate, wherein the soft magnetic layer has a thickness of 600 nm or more. . Also,
According to the present invention, there is provided a storage device incorporating a perpendicular magnetic recording medium in which a hard magnetic layer, a soft magnetic layer, and a perpendicular layer are sequentially laminated on a substrate, wherein the soft magnetic layer has a thickness of 600 nm or more. Provided. In each of the above structures, the material for forming the soft magnetic layer is preferably CoCrTa.

[0007]

FIG. 1 is a diagram showing an example of a layer structure of a perpendicular magnetic recording medium according to the present invention. In the figure, for example,
A hard magnetic layer 2, a soft magnetic layer 3, and a vertical layer 4 are sequentially laminated on a substrate 1, and a protective film 5 is formed on the vertical layer 4. The hard magnetic layer 2 has a function of fixing the magnetization of the soft magnetic layer 3 that is weak against an external magnetic field and stabilizing the magnetization of the perpendicular layer 4 as described above, and is formed of, for example, CoSm.

In the above-described perpendicular magnetic recording medium, the thickness of the soft magnetic layer 3 needs to be 600 nm or more. If the thickness of the soft magnetic layer 3 is less than 600 nm, the obtained perpendicular magnetic recording medium does not have sufficient signal stability against an external magnetic field, and demagnetization occurs. Therefore, when incorporated in an external storage device, high reliability cannot be realized. The material for forming the soft magnetic layer 3 is not particularly limited, and various materials such as CoZrNb and Permalloy can be used.
CoZrNb is preferred. Also, the vertical layer 4
Is formed of, for example, CoCrTa, and the protective film 5 is formed of, for example, SiO ₂ . In addition, the external storage device of the present invention can store the above-described perpendicular magnetic recording medium in, for example, an HDD
It is obtained by incorporating it in a high density,
And it is excellent in reliability.

<Example> A three-layer perpendicular magnetic recording medium shown in FIG. 1 was manufactured. That is, a CoSm ₁₇ hard magnetic layer 2 and a CoSm ₁₇ hard magnetic layer 2 were formed on a glass disk substrate 1 having a diameter of 3.5 inches.
Zr ₅ Nb ₄ soft magnetic layer 3 and CoCrTa of various compositions
Each of the vertical layers 4 was formed by a DC magnetron sputtering method, and a SiO ₂ protective film 5 was formed on the vertical layer 4 by an RF sputtering method to obtain a magnetic disk. At this time, the composition, magnetization Ms, film thickness δ, and coercive force H of the vertical layer 4 are obtained.
c, the thickness δ of the soft magnetic layer 3 and the thickness δ of the hard magnetic layer 2
Are shown in Table 1. As shown in Table 1, the characteristics of the perpendicular layer 4 and the hard magnetic layer 2 were kept substantially constant, and the thickness of the soft magnetic layer was varied.

[0010]

[Table 1]

Next, the stability of a recording signal with respect to an external magnetic field of each perpendicular magnetic recording medium obtained as described above was evaluated.
This evaluation test was performed using a Helmholtz coil at 0 to 70 [O
e), and each disk is rotated for 5 minutes in the magnetic field, and a change in 43 kfci signal output before and after the change (output before application is set to 100%, and values after application are indicated by%). Was carried out. The results obtained are shown in FIG. In the figures, Example 1 is indicated by Δ, Example 2 is indicated by □, Comparative Example 1 is indicated by Δ, and Comparative Example 2 is indicated by O.

As is clear from FIG. 2, CoZrNb
In the disks having a soft magnetic layer thickness of 300 and 200 nm (Comparative Examples 1 and 2), the largest demagnetization was caused by a magnetic field of 20 and 35 [Oe], and a considerably large demagnetization phenomenon was observed before and after that. Was done. On the other hand, CoZrN
(b) No demagnetization was observed in a disk having a soft magnetic layer thickness of 600 or 1000 nm (Examples 2 and 1) in an external magnetic field up to about 70 [Oe]. Thus, CoZrN
b As the thickness of the soft magnetic layer increases, the demagnetization decreases, and when the thickness reaches 600 nm, the demagnetization phenomenon disappears.
This is presumably because as the CoZrNb film thickness increases, the change in magnetization in the domain wall becomes smaller, and the leakage magnetic flux does not come out to the outside.

The magnetic field usually present in homes and offices is approximately several tens [Oe] (about 70 [Oe]).
e]), but from the results described above, C
It is presumed that by further increasing the oZrNb film thickness, a magnetic disk that is stable against an external magnetic field higher than that can be obtained. Further, by incorporating the thus obtained perpendicular magnetic disk into, for example, an HDD or the like, it becomes possible to obtain an external storage device having high density and excellent reliability.

[0014]

As described above in detail, according to the present invention, by setting the thickness of the soft magnetic layer, which is the intermediate layer of the three-layered perpendicular magnetic recording medium, to 600 nm or more,
An excellent magnetic recording medium in which signal deterioration does not occur even in the existing external magnetic field of about several tens [Oe] (about 70 [Oe]) can be obtained. Therefore, the perpendicular magnetic recording medium of the present invention can be used in a highly reliable recording system. This makes it possible to realize a portable large-capacity storage device.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a layer configuration of a perpendicular magnetic recording medium of the present invention.

FIG. 2 is a graph showing a relationship between a thickness of a soft magnetic layer and a change in output with respect to an external magnetic field in an example of the present invention.

[Description of Signs] 1 Substrate (glass disk substrate) 2 Hard magnetic layer (CoSm layer) 3 Soft magnetic layer (CoZrNb layer) 4 Vertical layer (CoCrTa layer) 5 Protective film (SiO ₂ layer)

Claims (4)

[Claims] In a perpendicular magnetic recording medium in which an in-plane hard magnetic layer, an in-plane soft magnetic layer, and a perpendicular magnetic recording layer are sequentially laminated on a substrate, the in-plane soft magnetic layer has a thickness of 600 nm.
A perpendicular magnetic recording medium characterized by the above. 2. The perpendicular magnetic recording medium according to claim 1, wherein the in-plane soft magnetic layer is formed of CoZrNb. 3. A storage device incorporating a perpendicular magnetic recording medium in which an in-plane hard magnetic layer, an in-plane soft magnetic layer and a perpendicular magnetic recording layer are sequentially laminated on a substrate, wherein the surface of the perpendicular magnetic recording medium is provided. A storage device, wherein the thickness of the inner soft magnetic layer is 600 nm or more. 4. The storage device according to claim 3, wherein said in-plane soft magnetic layer is formed of CoZrNb.