JP3052092B2 - Magnetic recording medium - Google Patents

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, and more particularly to a longitudinal recording type magnetic recording medium having a high recording density.

[0002]

2. Description of the Related Art Conventionally, a magnetic recording medium of the type described above has conventionally been formed on a non-magnetic material by a vapor deposition method or a sputtering method using Cr, Mo, W or an alloy film containing these as main components as an underlayer for crystal orientation. And a Co or Co alloy film is continuously formed on the underlayer to form a magnetic layer in which the C axis of the HCP phase is oriented substantially in the in-plane direction. It is frequently used as a hard disk medium.

At present, the composition of the magnetic layer is CoNiCr, CoCrTa, CoC
rPt, CoNiPt, CoCrPtTa and the like are used.

The mechanism of generating a coercive force in a conventional magnetic recording medium is as follows.

That is, when an underlayer made of Cr or the like is formed on a nonmagnetic substrate, the crystal orientation is performed so that the BCC (110) plane is parallel to the substrate surface, and columnar grains grow in the thickness direction of the underlayer. . When a Co alloy magnetic layer is continuously formed on the underlayer, the C-axis lattice distance of the HCP phase (002) of the magnetic layer is almost equal to the lattice distance of the underlayer (110) plane. The layers are grown epitaxially so that the C axis is parallel to the substrate plane. Since the C axis of the HCP of this Co alloy magnetic layer is an easy axis of magnetization, the Co alloy magnetic layer becomes an in-plane magnetized film. Further, since the underlayer of Cr or the like has a relatively clear columnar particle structure, the Co alloy magnetic film grown on the Cr film also has a particle structure isolated from each other.
Further, in a medium containing Cr in the Co alloy magnetic film, Co, which is a magnetic material, is segregated such that nonmagnetic Cr contained in the magnetic film surrounds the surroundings, and the magnetic layer itself has a particle structure isolated from each other. Form. Further, in a medium containing Pt in a Co alloy magnetic film, the HCP of Co in the magnetic layer
The (002) phase and the FCT (111) phase of CoPt coexist, and the domain wall is fixed to exhibit a high coercive force. As a result of a single domain grain structure having such crystal magnetic anisotropy, a high coercive force is generated.

However, even if the conditions for manufacturing the magnetic recording medium are optimized, the coercive force of the magnetic recording medium that can be used at present is 190 CoNiCr and CoCrTa.
About 0 Oe, CoCrPt, CoNiPt, CoCrP
The tTa is about 2400 Oe, and further higher coercive force has been desired.

The inventors of the present invention have conducted intensive studies with the aim of providing a magnetic recording medium capable of obtaining a higher coercive force. Recently, when Pt and B were simultaneously added to a Co-based alloy magnetic layer, It has been found that the coercive force increases and an extremely high coercive force is developed. This increase in coercivity is due to P
Only in the Co alloy magnetic layer to which t was simultaneously added, in the Co alloy magnetic layer not including Pt, no increase in coercive force was observed even when B was added. Further, as a result of X-ray analysis, when B was added, it was considered that the formation of the FCT phase of CoPt was promoted, and the coercive force was increased by the inclusion of the FCT phase. In addition, as a result of examining elements of Cr, Ni, and Ta which were conventionally known to have an effect of increasing the coercive force in this type of magnetic layer, it was found that the Co-Pt-B-based magnetic layer has a coercive force as before. It was found to be effective in increasing. Cr,
The effects of the elements Ni and Ta are considered to be the same as in the past.

[0008]

As described above, a magnetic layer in which Pt and B are simultaneously added to a Co alloy magnetic layer exhibits extremely high coercive force and is promising as a high recording medium.
Since t is very expensive, there is a problem that the price of the entire magnetic recording medium increases.

Accordingly, an object of the present invention is to provide a low-cost, high-coercivity magnetic recording medium.

[0010]

SUMMARY OF THE INVENTION The present invention provides an underlayer for crystal orientation comprising a thin film of Cr, Mo, W or an alloy thereof on a non-magnetic substrate , and at least
A magnetic recording medium comprising a magnetic layer in which a Co alloy layer formed of a thin film of a Co alloy containing Pd is formed continuously and the C axis of the HCP phase is oriented in a substantially in-plane direction. B is added to the components of the layer in an amount of 0.5 to 12 at% .

[0011] In addition to Pd, the Co alloy layer has a small amount of components.
At least Pt may be included. Also, in the Co alloy layer, Cr, Ni, also contain at least one kind of Ta
Good .

[0012]

This time, the present inventors added Pd to the Co-based alloy magnetic layer.
And B were added at the same time, the coercive force was increased, and an extremely high coercive force was developed. This increase in coercive force is observed only in the Co alloy magnetic layer to which Pd is simultaneously added, and in the Co alloy magnetic layer not containing Pd,
No increase in coercive force was observed even when B was added. Even if a part of Pd is replaced with Pt, an extremely high coercive force is similarly exhibited. Further, as a result of X-ray analysis, when B was added, the formation of the FCT phase of CoPd was promoted, and it is considered that the coercive force was increased by the inclusion of the FCT phase. In addition, as a result of examining elements of Cr, Ni, and Ta, which were conventionally known to have an effect of increasing the coercive force in this type of magnetic layer, it was found that the Co-Pd-B-based magnetic layer still has the same coercive force. It was found to be effective in increasing. The effects of the elements Cr, Ni, and Ta are considered to be the same as in the past.

Further, the inventors have measured the in-plane coercive force in the case where there is no underlying film for crystal orientation, and as a result, it has been found that the addition of B lowers the coercive force.
Therefore, in the present invention, the underlayer for crystal orientation is indispensable.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic recording medium according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0015] First, NiP is electrolessly plated on Al by DC magnetron sputtering, and a Cr underlayer is formed on a non-magnetic substrate whose surface is polished by 1500.
{Circle around (5)} Co-alloy magnetic layers of various compositions were continuously formed at 500 °, and C layer as a protective film was continuously formed at 300 °. Ultimate vacuum is 5 ×
10- ⁶ Torr or less, an argon pressure during sputtering 5m
Torr, the substrate temperature was 290 ° C., and a bias voltage of −300 V was applied to the substrate. The above sputtering conditions are the most common manufacturing conditions for this type of recording medium. Here, C
The following experiment was performed by changing only the composition of the o-alloy magnetic layer. For comparison, those without a Cr underlayer were also manufactured as comparative examples.

First, Co-10 at% Pd and Co-1
By changing the addition amount X of B to 5 at% Pd,
Co-10at% Pd-Xat% of various composition ratios
B, Co-15 at% Pd-Xat% B magnetic films were prepared, and the in-plane coercive force of the obtained magnetic recording medium, that is, the coercive force in the direction parallel to the film surface of the magnetic recording medium was measured. The result is
Each is shown in the graph of FIG.

As can be seen from the graph of FIG.
By adding 5 to 12 at%, the coercive force of the magnetic recording medium is increased as compared with the case where B is not added.
The coercive force reaches a maximum value in the vicinity of at%, and is improved by about 600 Oe as compared with the case where B is not added.

Next, the addition amount of B in the magnetic layer is 3 at.
%, And the amount of Pd added was changed to produce a magnetic film, and the in-plane coercive force of the obtained magnetic recording medium was measured. The results are shown in the graph of FIG.

As can be seen from FIG. 2, the range of the added amount Y of Pd at which a high coercive force can be obtained is 3 to 30 at%.

Next, Co-15 at% (Pt + Pd)-
3 at% B (Example) and Co-15 at% (Pt + P
d) A magnetic film was prepared by changing the ratio of Pt to Pd with the composition of Comparative Example, and the in-plane coercive force of the obtained magnetic recording medium was measured. The results are shown in the graph of FIG. As can be seen from FIG. 3, the coercive force obtained by adding B was as high as 500 to 900 Oe in all the compositions, as compared with the one containing no B. Furthermore, even if Pt is replaced with Pd by half, the coercive force of B-added hardly decreases and a high coercive force can be obtained at low cost.

Next, Co-7.5 at% Pt-7.5a
By changing the addition amount X to t% Pd, C
o-7.5at% Pt-7.5at% Pd-Xat% B
A magnetic film was prepared, and the in-plane coercive force of the obtained magnetic recording medium was measured. The results are shown in the graph of FIG. As can be seen from the graph of FIG. 4, this Co-7.5 at% Pt
Also in the case of the -7.5 at% Pd-based magnetic layer, the coercive force increased with the addition of B, and reached the maximum value when the addition amount was 3 to 5 at%.

Next, a typical composition of a Co alloy magnetic layer to which Cr, Ni and Ta are added, which has been conventionally effective for improving the coercive force, that is, Co-10 at% Cr
-15at% Pd-Xat% B, Co-10at% Cr
-7.5at% Pt-7.5at% Pd-Xat% B,
Co-20at% Ni-7.5at% Pt-7.5at
Pd-Xat% B, Co-10at% Cr-2at% T
a-7.5at% Pt-7.5at% Pd-Xat% B
The magnetic film of each composition was prepared by changing the addition amount X of each B, that is, the composition of B, and the in-plane coercive force of the obtained magnetic recording medium was measured. The results are shown in the graph of FIG. From FIG. 5, B is in the range of 0.5 to 12 at%.
The coercive force of the magnetic recording medium can be increased by adding
Increase compared to the additive one.

Next, as a comparative example, there was no Cr underlayer,
Co-15at% Pd-Xat% B, Co directly on the substrate
A magnetic film of each composition was prepared by changing the addition amount X of each of B, ie, the composition of B, of -7.5 at% Pt-7.5 at% Pd-Xat% B, and the surface of the obtained magnetic recording medium. The internal coercive force was measured. The results are shown in the graph of FIG. As can be seen from FIG. 6, the coercive force of the magnetic recording medium decreases with the addition of B. This indicates that the addition of B increases the coercive force only when a Cr underlayer exists.

Finally, for comparison, a Pd-free Co-Xat%
B, Co-12at% Cr-2at% Ta-Xat% B
The coercive force of the magnetic layer formed by adding each of the above B in various amounts was measured. The result is shown in FIG. As can be seen from the graph of this figure, when B is added to a Co film to which Pd is not added, the addition amount increases and the coercive force decreases. This indicates that the addition of B increases the coercive force when added simultaneously with Pd. Although the effect of increasing the coercive force can be obtained by replacing Pd with Pt, Pt is expensive and is not economically suitable.

In the above embodiment, the Cr layer was used as the underlayer. However, the Cr and M layers which control the crystal orientation of the C axis of the magnetic layer formed continuously thereon substantially in the film plane direction are used.
You may use o, W, these alloys, and the alloy which has these alloys as a main component.

[0026]

According to the present invention, an underlayer for crystal orientation is formed on a non-magnetic substrate, and Pd continuously formed thereon is formed.
By adding B to the Co-based alloy layer containing, the in-plane coercive force of the obtained magnetic recording medium can be increased with a low-cost material, and the in-plane recording type inexpensive magnet having a high recording density can be used. A recording can be obtained.

[Brief description of the drawings]

FIG. 1 shows a Cr underlayer formed on a nonmagnetic substrate, and Co-15at% Pd-Xat% B continuously formed thereon.
In the magnetic layer of each composition composed of
FIG. 4 is a graph showing the relationship between the amount of element added and the in-plane coercive force of the obtained magnetic recording medium.

FIG. 2 shows a Cr underlayer and C continuously formed thereon.
FIG. 7 is a graph showing the relationship between the amount of Pd element added to the magnetic layer and the in-plane coercive force of the obtained magnetic recording medium in a magnetic layer composed of o-3 at% B-Yat% Pd.

FIG. 3 shows a Cr underlayer and C continuously formed thereon.
o-15 at% (Pt + Pd) -3 at% B, Co-1
In a magnetic layer composed of 5 at% (Pt + Pd),
It is a graph which shows the relationship of the coercive force with respect to the composition ratio of Pt and Pd.

FIG. 4 shows a Cr underlayer and C continuously formed thereon.
o-7.5at% Pt-7.5at% Pd-Xat% B
FIG. 4 is a graph showing the relationship between the amount of B added to the magnetic layer and the in-plane coercive force of the obtained magnetic recording medium in the magnetic layer composed of.

FIG. 5 is a graph showing the relationship between the amount of B added to the magnetic layer and the coercive force in a Cr underlayer and a magnetic layer of each composition continuously formed on the underlayer.

FIG. 6: Co-7.5 at% Pt-7.5 at% Pd-Xat directly on a non-magnetic substrate without forming a Cr underlayer.
% B and Co-15 at% Pd-Xat% B, the amount of B added to the magnetic layer,
FIG. 4 is a graph showing the relationship between the in-plane coercive force of the obtained magnetic recording medium.

FIG. 7 shows Co-12 at% C formed on a Cr underlayer.
r-2at% Ta-Xat% B and Co-Xat% B
FIG. 4 is a graph showing the relationship between the amount of B added to the magnetic layer and the in-plane coercive force of the obtained magnetic recording medium in a magnetic layer having a composition.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masanori Hashimoto 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Pref. Japan Vacuum Engineering Co., Ltd. Chiba Super Materials Research Laboratory (56) References JP-A-61-246914 (JP, A) JP-A-63-79229 (JP, A) JP-A-2-227826 (JP, A) JP-A-63-184913 (JP, A) JP-A-2-161617 (JP JP, A) JP-A-4-221418 (JP, A)

Claims (3)

(57) [Claims] An underlayer for crystal orientation comprising a thin film of Cr, Mo, W or an alloy thereof on a non-magnetic substrate , and a thin film of a Co alloy containing at least Pd on the underlayer for crystal orientation. Co alloy layer is formed continuously, and HC
In a magnetic recording medium provided with a magnetic layer in which the C axis of the P phase is oriented substantially in-plane, B is added to the components of the Co alloy layer.
A magnetic recording medium, wherein 0.5 to 12 at% is added . 2. The composition of the Co alloy layer contains a small amount of Pd in addition to Pd.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium contains at least Pt . 3. The Co alloy layer contains Cr, Ni, and Ta.
2. The composition according to claim 1, wherein the composition contains at least one kind.
Or 2 magnetic recording media.