JPH07106127A - Magnetic film and magnetic recording medium using thereof - Google Patents

Abstract

PURPOSE:To provide a metal thin film type magnetic recording medium, to be used for a hard disk device and the like, suitable for high density recording having high coercive force and low modulation noise. CONSTITUTION:The title magnetic recording medium is provided with a non- magnetic substrate and a metal thin film type magnetic film formed on the non-magnetic substrate. The magnetic film has the composition of the formula Co100-x-ySmxMy (M indicates the element having at least a kind selected from B, C, N, O, P, S, Zr, Hf, Fe, Ni, V, Nb, Ta, Cr, Mo, W, Al, Si, Cu, Zn, Ru and Pr, x and y indicate the number which satisfy 0<x<30wt.% and 0<=y<=30wt.%), the magnetic film is at least separated into two phases having different Co content, its Co content of Co-rich phase is 70wt.% or more, and the Co content of Co-poor phase is 70wt.% or less. The Co-rich phase of high coercive force mainly functions as a magnetic recording phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a metal thin film type magnetic film,
And a metal thin film type magnetic recording medium used in a magnetic recording apparatus.

[0002]

2. Description of the Related Art In recent years, the range of application of magnetic recording devices such as magnetic disk devices, floppy disk devices, magnetic tape devices, magnetic card devices, and magnetic drum devices has increased.
At the same time, the magnetic recording media used in these devices are being adapted to high recording densities. Various methods such as thinning the medium, increasing the residual density, and increasing the coercive force are conceivable for improving the recording density, but the high recording density of the current mainstream coating type media has reached the limit. Development of a metal thin film type magnetic recording medium having a high coercive force and the like is in progress.

Currently, CoNi and CoNi are used as metal thin film type magnetic recording media used in high density type hard disk drives.
A medium having a sputtered film such as Cr, CoCrTa, CoCrPt, CoPt, CoPtO 2, and CoPtCrO as a magnetic film is known, but a magnetic film having a larger coercive force is required to further improve the recording resolution. ing.

Further, as a characteristic required for increasing the density of a magnetic recording medium, there is a high coercive force and a reduction in modulation noise. In general, a metal thin film type magnetic recording medium has a larger interaction between magnetic particles than a coating type medium.
It has a drawback that the modulation noise tends to be large.
As a method of reducing the modulation noise, it has been considered to cut off the interaction between the magnetic particles by using an underlayer film or by selecting the sputtering conditions of the magnetic film. Further, it has been considered to make the bit shape uniform by making the magnetic particles finer, thereby reducing the modulation noise.

However, the fineness of the magnetic film often results in loss of isolation of the magnetic particles, often accompanied by a decrease in coercive force. Therefore, after making the magnetic film finer,
In order to obtain a high coercive force, it is necessary to use a magnetic material having a large crystal magnetic anisotropy.

By the way, Sm-Co type alloys (SmCo ₅ , Sm ₂ Co _17, etc.) are known as materials having large magnetic anisotropy, and have been often used in recent years as permanent magnet materials. As a thin-film magnet formed by sputtering, Xe
By performing sputtering in a mixed gas of Ar and Ar,
A 6 μm-thick magnetic film (coercive force 6000 Oe) having a Sm ₂ Co ₁₇ crystal structure was prepared (J.Appl.Phys.67,4969 (199
(See 0)) is known. As an example of using the Sm-Co alloy as the magnetic film of the magnetic recording medium, a high coercive force of 2400 Oe was realized by using a Cr underlayer (V
elu and Lambeth, J. Appl. Phys. 69, 5175 (1991)) and the like are known.

[0007]

However, as a result of studies by the present inventors, among the magnetic recording media using the above-described Sm-Co alloy, the former magnetic film having a crystal structure of Sm ₂ Co ₁₇ was found to be It was found that the magnetic interaction due to the crystal structure composed of the intermetallic compound is large and the suppression of the modulation noise is insufficient. Also, since the latter magnetic film is composed of an amorphous single-phase Sm-Co alloy formed on the Cr underlayer, there is a problem that the magnetic interaction is large and the modulation noise is not improved. It became

As described above, as a matter of fact, as a magnetic recording medium using Sm-Co, a medium having a high coercive force and a magnetic film having a small modulation noise has not been obtained.

The present invention has been made in order to solve such a problem, and has a high coercive force and a small modulation noise and is suitable for high density magnetic recording. The purpose of the present invention is to provide a conventional magnetic recording medium.

[0010]

The magnetic film of the present invention has a general formula: Co _100-xy Sm _x M _y (1) (where M is B, C, N, O, P, S, Zr, Hf, Fe, N
i, V, Nb, Ta, Cr, Mo, W, Al, Si, Cu, Zn, Ru and
X and y are at least one element selected from Pr
(Indicates a number that satisfies 0 <x <30at% and 0 ≦ y ≦ 30at%)
Is characterized in that it has a composition substantially represented by and is separated into at least two phases having different Co contents.

Further, the magnetic recording medium of the present invention comprises a non-magnetic substrate and a metal thin film type magnetic film provided on the non-magnetic substrate, wherein the magnetic film has the above-mentioned (1). It is characterized in that it has a composition substantially represented by the formula and is separated into at least two phases having different Co contents.

The metal thin film type magnetic film in the magnetic recording medium of the present invention is composed of the Sm-Co type alloy represented by the above formula (1) and is separated into two or more phases having different Co contents. It has a fine structure. The fine structure of the magnetic film made of such an Sm-Co alloy is schematically shown in FIG. Further, FIG. 2 shows a TEM photograph of an example of the magnetic film made of the Sm-Co alloy. As shown in FIG. 1, the magnetic film of the present invention contains a first phase A (black phase in FIG. 2) having a relatively high Co content and a high coercive force, and a relatively low Co content and a low Co content. It has a saturated magnetic flux density or a non-magnetic second phase B (white phase in FIG. 2). Here, the Co content in the first phase A is preferably 70 at% or more, and therefore the Co content in the second phase is preferably less than 70 at%.

The first phase A which mainly functions as a magnetic recording phase
Is preferably composed of fine crystal particles having a particle size of 50 nm or less, for example. When the particle size is 50 nm or more, the suppression of modulation noise becomes insufficient. Therefore, more preferably 30
nm or less, more preferably 10 nm or less. In addition, the particle size referred to here indicates a diameter of a sphere in contact with the particle. Second
The phase B is distributed in the grain boundaries of the first phase A and divides the magnetic phase A. In this way, by dividing the magnetic phase A by the phase B having non-magnetic or low saturation magnetic flux density and suppressing the interaction between the magnetic phases, it is possible to reduce the modulation noise. The area ratio of the first phase (magnetic phase) A is at least 50% of the entire magnetic film, but within a range in which the division state of the first phase A by the second phase B can be maintained, It is preferable that a large amount is present. Specifically, the first phase A
The area ratio is preferably 70% or more. More preferably, it is 80% or more. Also, the first phase A with a high Co content
Does not necessarily have to be composed of crystal particles of Sm-Co alloy, but the first phase A should be composed of amorphous and the second phase B should be composed of crystal particles of Sm-Co alloy. You can also When the first phase A is composed of crystalline particles, the second phase B has an amorphous structure,
It may also have a crystal structure. Note that Co may be an intermetallic compound with Sm or may be present as a solid solution of Co. At this time, if the amount of the additive other than Co is large, the saturation magnetization is reduced, so that when used as a medium, the output is reduced and the S / N is reduced. Therefore, the values of x and y in the equation (1) are 0 <x <30 and 0 ≦ y ≦ 30. Further, for the same reason and because a large coercive force cannot be obtained when the amount of Sm is small, preferably 3 <x <20, 0 ≦ y ≦ 20, more preferably 5 <x <20, 0 ≦ y ≦ Is 10.

The alloy constituting the magnetic film of the present invention is
Although it is basically an Sm-Co alloy, as shown in equation (1), in order to promote phase separation of the Sm-Co alloy and further reduce modulation noise, M elements (B, C, N, O, P, S, Z
r, Hf, Fe, Ni, V, Nb, Ta, Cr, Mo, W, Al, Si, C
Alloys in which u, Zn, Ru, Pr, etc.) are added in a predetermined range can be used. The thickness of the magnetic film is preferably 0.5 μm or less. High density magnetic recording can be realized by using such a thin magnetic film.

An example of the structure of the magnetic recording medium of the present invention is shown in FIG.
Shown in. In FIG. 3, reference numeral 1 indicates a non-magnetic substrate, and 2
Is a base film formed thereon as needed. Further, reference numeral 3 indicates a metal thin film type magnetic film, and reference numerals 4 and 5 indicate a protective film made of carbon and a lubricating film made of a lubricant such as perfluoroether. The non-magnetic substrate 1 is not particularly limited in material as long as it is a substrate made of a non-magnetic material, and a glass substrate, a ceramic substrate, a carbon substrate, an organic film such as a synthetic resin film, and a nickel phosphorus layer formed on the surface. It is possible to use a metal plate or the like such as an aluminum plate that has been cut.

In the magnetic recording medium of the present invention,
In order to enhance the orientation of the magnetic film 3 and improve the coercive force of the medium, the underlayer film 2 made of Cr, Ti, Al, Ge, Pd or the like is provided on the non-magnetic substrate 1, and the magnetic film 3 is provided thereon. It may be formed. That is, the magnetic film 3 in the present invention is provided directly on the non-magnetic substrate 1 or is provided on the non-magnetic substrate 1 via the underlayer film 2. There is no particular upper limit to the thickness of the base film 2, but it is preferable to set the thickness to 500 nm or less for practical use.

The magnetic recording medium of the present invention can be obtained by forming a magnetic film having a desired composition on the above-mentioned non-magnetic substrate or underlayer by a thin film forming technique. As a method of forming the magnetic film, it is preferable to apply a magnetron sputtering method using an alloy target or the like, and it is also possible to apply an ion beam sputtering method, a vapor deposition method or the like. By controlling the conditions at the time of forming the magnetic film as described above, at least 2
A magnetic film having a structure separated into two phases can be obtained. For example, in the case of forming a film by a sputtering method, by appropriately setting the sputtering conditions (gas pressure, film forming rate, sputtering gas), the type of the base film, etc., so that at least one phase has a crystal structure, A magnetic film composed of an Sm-Co based alloy separated into at least two phases can be obtained. Also,
By further changing the sputtering conditions and selecting additional elements, magnetic films with three or more phases separated can be obtained.

[0018]

In the magnetic recording medium of the present invention, the magnetic film is made of a high coercive force Sm-Co alloy, and the fine structure of this magnetic film has a relatively high Co content and a high coercive force. It has a structure in which it is separated into a phase having a low saturation magnetic flux density and a nonmagnetic phase having a relatively small Co content. Then, the second phase having a low Co content and the first phase having a high Co content
The magnetic interaction between the first phases responsible for magnetic recording is disrupted because of the structure surrounding the phase (1), and thus the modulation noise can be reduced.

Further, in the conventionally used magnetic film such as CoCrTa or CoPt system, the magnetic isolation between particles is lost due to atomization, and the coercive force deteriorates the performance as a magnetic recording medium. However, in the magnetic film of the present invention using the SmCo alloy, the magnetic phase can be made finer with the high coercive force, and the modulation noise can be reduced while maintaining the high recording density.

[0020]

EXAMPLES Examples of the present invention will be described below. Example 1 A disk substrate made of glass was set in a DC magnetron sputtering apparatus, evacuated to a high vacuum of 1 × 10 ⁻⁵ Torr or less, and then an Sm—Co alloy target having a composition of 17 at% Sm—Co,
Alternatively, a composite target in which small pieces of Sm were arranged on a Co disk was used, and sputtering was performed using argon gas.

Then, the sputtering gas pressure, the sputtering current,
By changing the conditions such as film formation speed, substrate temperature, and bias voltage to the substrate, the film can be formed into multiple magnetic films with different microstructure, composition and magnetic anisotropy.
m) got. Table 1 shows the composition of the film, the sputtering conditions, and the fine structure of the film. The magnetic films of this example all had a microstructure separated into two phases having different Co contents. As an example, in Example 1, the sputtering conditions were a partial pressure of argon gas of 3.0 Pa and a sputtering current of 6.0 A. In addition,
The average composition of the obtained magnetic film was analyzed by X-ray fluorescence analysis and X-ray analysis.
PS analysis was performed, and the microscopic composition separation of the film was examined by EDX analysis of an analytical electron microscope. Co-rich phase and Co-poor
The area ratio of the phases was measured by EDX of the above-mentioned analytical electron microscope to examine the composition of each crystal grain and amorphous, and
It was calculated from the area ratio of the phase of t% Co or more (phase A) and the phase of less than 70at% Co (phase B).

As a comparison with the present invention, a magnetic film having an amorphous structure was produced in the same manner as in Example 1 by controlling the sputtering conditions.

A SiO ₂ protective film having a thickness of 15 nm and a thickness of 0.
Lubricating films made of 2 μm perfluoroether-based lubricant were sequentially formed, and magnetic recording media were produced.

Regarding the magnetic recording medium thus obtained,
The coercive force and the S / N ratio were measured respectively. The coercive force H _c is measured using a sample vibrating magnetometer, and S / N
The ratio was measured with a flying height of 0.07 μm using a thin film head with a gap length of 0.3 μm and a track width of 6 μm, and the value at 60 kFCI is shown. The results of these measurements are also shown in Table 1.

[0025]

[Table 1]

As is clear from Table 1, the magnetic film made of the Sm-Co alloy having the amorphous structure obtained in Comparative Example 1 was
While the coercive force is small and the S / N ratio is small, it can be seen that the two-phase separation type magnetic film obtained in the A group of Example 1 has a large coercive force and a large S / N ratio. .

When the crystal structure of the magnetic film obtained in Example 1 was examined by X-ray diffraction (using Cu-Kα ray), intermetallic compounds such as SmCo ₅ and Sm ₂ Co ₁₇ were found. No peak was observed, and a broad peak was observed near the hcpCo (002) peak. Example 2 On the target of Sm-Co alloy, elements to be added (B,
C, Cr, Pr, etc.) are each used in the same manner as in Example 1 except that a composite target on which small pieces of C, Cr, Pr, etc. are respectively used is used, or by using a mixed gas of argon gas and oxygen or nitrogen, and the results are shown in Table 2. A magnetic film having the composition and structure shown was produced, and a magnetic recording medium was produced in the same manner as in Example 1. The coercive force and S / of the magnetic recording medium thus obtained
Each N ratio was measured. The measurement results are also shown in Table 2.

[0028]

[Table 2]

As is clear from Table 2, in Sm-Co alloy
By adding an appropriate amount of elements such as B, C, Cr, and Pr, phase separation is promoted and fine magnetic particles are generated, and a non-magnetic phase is precipitated between these particles, resulting in interaction between particles. It can be seen that the modulation noise is smaller because it is cut off. The same applies to the two-phase separation type magnetic film made of the Sm-Co alloy containing nitrogen and oxygen.
The magnetic film of No. 2 also has a larger coercive force and smaller modulation noise than the magnetic film of Comparative Example 1. Example 3 A 300 nm thick Cr underlayer film was formed on a glass disk substrate by a DC magnetron sputtering method, and then Sm- was formed on the underlayer film in the same manner as in Examples 1 and 2.
A magnetic film made of a Co alloy, or Sm-Co alloy with N, O,
A magnetic film of an alloy to which B, C, Cr, Pr, etc. were added was formed.
Then, the composition and fine structure of the film were changed as shown in Table 3 by changing the gas pressure during sputtering, the sputtering current, and the like. Example 1 using each of these magnetic films
A magnetic recording medium was manufactured in the same manner as above, and the coercive force and S / N ratio of the magnetic recording medium were measured. The measurement results are also shown in Table 3.

[0030]

[Table 3]

As is clear from Table 3, S is deposited on the Cr underlayer.
It was confirmed that by forming a two-phase separation type magnetic film made of an m-Co alloy, the coercive force was significantly improved, noise could be reduced, and the magnetic characteristics were significantly improved.

In this embodiment, the substrate temperature is set to 2
Two-phase separation is realized by setting the temperature to 00 ° C, but it can also be obtained by appropriately selecting other means, such as the argon pressure and the distance between the substrate and the target.

[0033]

As described above, according to the magnetic recording medium of the present invention, since the magnetic film is composed of the SmCo alloy having a large crystal magnetic anisotropy, a large coercive force can be obtained even if the magnetic phase is miniaturized. You can In addition, the magnetic film is separated into two or more phases with different Co contents, and a low saturation magnetic flux density or non-magnetic phase is present so as to surround the finely divided magnetic phase. It is possible to reduce the modulation noise because the dynamic interaction is divided and reduced. With these, it becomes possible to provide a magnetic recording medium capable of high density recording and capable of magnetic recording with an improved S / N ratio.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a fine structure of a magnetic film in a magnetic recording medium of the present invention.

FIG. 2 is a TEM photograph showing an example of a fine structure of a magnetic film in the magnetic recording medium of the present invention.

FIG. 3 is a cross-sectional view showing a structural example of a magnetic recording medium of the present invention.

[Explanation of symbols]

A: a first phase having a relatively high Co content and a high coercive force B: a low saturation magnetic flux density or a nonmagnetic second phase having a relatively low Co content 1 ... a nonmagnetic substrate 2 …… Undercoat film 3 …… Magnetic film 4 …… Protective film 5 …… Lubrication film

Claims (6)

[Claims] 1. A general _{formula: Co 100-xy Sm x M} y ( wherein, M is B, C, N, O, P, S, Zr, Hf, Fe, N
i, V, Nb, Ta, Cr, Mo, W, Al, Si, Cu, Zn, Ru and
X and y are at least one element selected from Pr
(Indicates a number that satisfies 0 <x <30at% and 0 ≦ y ≦ 30at%)
A magnetic film having a composition substantially represented by and separated into at least two phases having different Co contents. 2. The magnetic film according to claim 1, wherein the first phase having a Co content of 70 at% or more and the Co content of 70 at% are used.
A magnetic film having at least a second phase of less than. 3. The magnetic film according to claim 2, wherein the area ratio of the first phase is 50% or more. 4. A non-magnetic substrate, a magnetic recording medium comprising a magnetic film of a metal thin film type provided on the nonmagnetic substrate, the magnetic layer has the general _{formula: Co 100-xy Sm x M} y (Where M is B, C, N, O, P, S, Zr, Hf, Fe, N
i, V, Nb, Ta, Cr, Mo, W, Al, Si, Cu, Zn, Ru and
X and y are at least one element selected from Pr
(Indicates a number that satisfies 0 <x <30at% and 0 ≦ y ≦ 30at%)
A magnetic recording medium having a composition substantially represented by and separated into at least two phases having different Co contents. 5. The magnetic recording medium according to claim 4, wherein the magnetic film comprises a first phase having a Co content of 70 at% or more, and Co.
A magnetic recording medium having at least a second phase having a content of less than 70 at%, wherein the first phase mainly functions as a magnetic recording phase. 6. The magnetic recording medium according to claim 5, wherein the area ratio of the first phase is 50% or more.