JPS61110329A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the magnetic characteristic of a vertically magnetizable FexN film by depositing at least one intermediate film layer between a high permeability magnetic film and the FexN film. CONSTITUTION:A nonmagnetic substrate 1 is housed in an RF sputtering device and the high permeability film, intermediate film and FexN film are continuously sputtered by a sputter target 2. The material of which the average nearest inter-atom distance (DCA) is 2.5-3.5Angstrom , for example, elements such as V, Ru, Zn - etc. and the metallic nitride and metallic oxide thereof are used as the material for the intermediate film. The C-axis of the FexN film is oriented perpendicularly to the film plane when such intermediate film is intervened by which the upper limit value of Bs to be formed as the vertically magnetizable film is made as high as >=7,000G and the magnetic characteristic of the FexN film is improved.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention provides a magnetic material with high permeability suitable for perpendicular magnetic recording of magnetic disks, floppies, etc. and FexN (x=2 to 3
) film.

In this specification, FexN to which 10J7tl% or less of Cr or the like is added is also collectively referred to as FexN.

[Background of the invention]

There has been a remarkable improvement in recording density in the field of magnetic recording. In particular, the perpendicular magnetic recording method proposed by Iwasaki et al. of Tohoku University differs from the currently-practical in-plane recording method in that the higher the recording density, the smaller the self-demagnetizing effect.

It is attracting attention as a future high-density magnetic recording method and is being actively researched.

To realize this perpendicular magnetic recording, a perpendicularly magnetized film having an axis of easy magnetization perpendicular to the magnetic film surface is required as a recording medium. Furthermore, a so-called two-layer medium in which a high permeability magnetic film is deposited under the perpendicularly magnetized film is composed only of the perpendicularly magnetized film. It is considered to be highly practical because the reproduction output when recording and reproducing using a magnetic head is more than twice as high as that of a so-called single-layer medium.

High permeability magnetic films include ferrite, Fa, N2
゜Permalloy, Sendust, (Fe, Goo N1) -
(si, B, CI PT AQ-B) system amorphous alloy.

(Fa, Co, N1)-(Zr, Hf+ Y+ Tit
Nb, Ta, W+ V+ Mo, Cr) based amorphous alloy.

A material coated with a known high permeability magnetic material for magnetic heads such as FexC is used. The film thickness is usually 0
Those with a diameter of 65 to 2.0 μm are used.

A physical vapor deposition method (sputtering method) is used for the perpendicular magnetization film.

(vacuum deposition method, etc.), plating method or chemical vapor deposition method (CVD, etc.)
Go-Cr, Co-Cr-Rh, Go-
V+ Co-Ru, Go-Or CotG o -N
Alloy films such as i-Mn-P are known.

However, such perpendicular magnetization films are all based on Co, and since Co is a scarce resource, there have been problems with cost and stable supply.

In addition, with Co-based materials, there is a concern about heating demagnetization and pressurization demagnetization.

One of the ways to try to solve these problems.

There is a FexN perpendicularly magnetized film using Fe as a base instead of Co (Japanese Patent Application No. 102,675/1983). It is slightly inferior to the Cr film.

[Purpose of the invention]

The object of the present invention is to provide an average of at least one layer of high permeability magnetic film and FexN perpendicular magnetization amount! An intermediate film of metal, metal nitride, metal oxide, etc. having a distance between adjacent atoms of 2.5 to 3.2 was deposited. The object of the present invention is to provide a perpendicular magnetic recording medium with better characteristics.

A dual-layer film medium has a high reproduction output when recorded and reproduced with a magnetic head, and is somewhat rigid, so it is mainly used for magnetic disks, but this does not preclude its use for magnetic tapes, floppies, etc.

[Summary of the invention]

The reason why the F a xN (x=2 to 3) film becomes a perpendicular magnetization film is considered as follows. When a cross section of a FexN film fabricated by physical vapor deposition is observed using an SEM, a columnar structure in which crystal grains grow in a direction perpendicular to the film surface is observed. One of the reasons why the FexN film becomes a perpendicular magnetization film is the microscopic shape anisotropy due to the columnar crystals (anisotropy based on the shape of each columnar crystal).Furthermore, the size of the perpendicular anisotropy is Ku) is.

Magnetostatic energy 2π when magnetization is perpendicular to the film surface
The following (1
The second reason is that the relationship in the equation ) is satisfied.

Ku > 2gM5” - (1) Normal,
In the case of a Fe thin film, even if the Fe columnar crystals are ideally aligned perpendicular to the film surface, if bulk values are used for Ku and Ms, the values on the left and right sides of equation (1) are 9 x 10, respectively.
erg/cc, 1.8 x 10'erg/cc
The relationship in equation (1) cannot be satisfied, and the ideal columnar crystal (major axis length/minor axis length ~oo) is not perfectly oriented in the direction perpendicular to the film surface. (1)
The left side of the equation is expected to be significantly less than 9 x 10'erg/cc.

It is thought that the effect of adding N is to promote alignment of columnar crystals perpendicular to the film surface and to lower Ms to such an extent that formula (1) holds. The segregation of N at the grain boundaries of columnar crystals is also considered to be one of the reasons why the FexN film becomes a perpendicularly magnetized film.

At that time, FexN has a hexagonal crystal structure, and
If the C-axis is oriented perpendicular to the film surface, it is a hexagonal system Fax.
Since the crystal anisotropy of N is added to the above-mentioned microscopic shape anisotropy, the perpendicular magnetic anisotropy (Ku.

(left side of equation (1)) becomes large, and even if Ms is large, Fe
The xN film becomes a perpendicularly magnetized film. However, the special application
In the FexN film obtained by the method shown in No. 2675, there was no cm orientation. This is the upper limit value (6
500G) is a typical perpendicular magnetization film, which is a Go-Cr film.
This is considered to be the reason why the value is slightly smaller than the upper limit of s.

In order to improve the characteristics of the FexN film, we investigated an intermediate film between the FexN film and the high permeability magnetic film.

As a result, the electrical resistance of the intermediate film is I x 10-'
Below Ω, the average distance between nearest atoms is 2.5 to 3.2
By using films made of metals, metal nitrides, metal oxides, etc., the C-axis of the hexagonal FexN film is oriented perpendicular to the film surface, and the upper limit of Bs is high, making the FexN film a perpendicularly magnetized film. It became clear that something was going to happen. This is considered to be because the above-mentioned crystal anisotropy is added to the microscopic shape anisotropy, resulting in an increase in perpendicular magnetic anisotropy.

FIG. 1 is a plot of the relationship between the distance between the nearest atoms of the intermediate film and the maximum value of Bs at which the FexN film becomes a perpendicularly magnetized film. As can be seen from Figure 1, when an intermediate film with an average nearest neighbor atomic distance (DCA) of 2.5 to 3.2 is used, the upper limit of Bs at which the FexN film becomes a perpendicularly magnetized film is 700.
It becomes larger than 00.

This is XJ! As a result of diffraction analysis, it was revealed that the C-axis of the FexN film was oriented in the direction perpendicular to the film surface. This C-axis orientation is considered to be one of the reasons why the upper limit of Bs at which the FexN film becomes a perpendicularly magnetized film is increased.

When the average nearest neighbor atomic distance is 2.6S to 2.85, the upper limit of B8 at which the FexN film becomes a perpendicularly magnetized film becomes even larger, reaching a maximum of 80,000 or more.

The membrane and shite of people with DCA of 2.5 to 3.2 are V.

Ru, Zn, Os, Rh, Ir, Mo, WtRe.

Pt+ Nb+ Sn, Ta, An, Au, Ag5
Examples include Ti and nitrides and oxides of these elements.

Among these, Zn, Mo, wl Nb+ TanAl, T
i, Sn or Sn oxide are more preferred because they are inexpensive.

By mixing two or more types of elements, the average nearest atomic distance is 2.
．． It goes without saying that these metals and metal oxides are also effective as 5 to 3.2 people, and it is more preferable if this intermediate film is a high magnetic permeability film.

bcp and tcc for crystal structures such as metal nitrides.

bce, amorphous, etc., but hcp and amorphous are more preferred.

The thickness of the intermediate film is preferably 0.01 to 0.1 μm, more preferably 0.01 to 0.05 μm. 0.0
A film thickness of 1 to 0.1 μm is preferable.

If the thickness is less than 0.01 μm, the effect as an interlayer film is small;
This is because if the thickness exceeds 0.1 μm, the magnetic interaction between the high permeability magnetic film and the FaxN perpendicular magnetization film becomes small, and the reproduction output when recording and reproducing with a magnetic head becomes small. This intermediate film may be one layer, but the total film thickness is 0.01 to 0.1
This does not exclude the use of two layers within the range of μm.

After forming the middle 11 JII film, a physical vapor deposition method (sputtering method) is used.

evaporation method, etc.), chemical vapor deposition method (CVD method), plating method, electrodeposition method such as electroless plating method, etc., and any method can be selected considering the overall process.

The FexN film has a thickness of 0.1 μm or more, an N content of 20 to 32 at%, and a saturation magnetic flux density of 2000
~10000G may be used, but N
The content of is 22 to 28 at%, Bs is 6500 to 100
00G is more preferable because it increases the reproduction output.Also, for the purpose of improving the corrosion resistance of the FexN film, Cr, Ni, Co+Bit platinum elements, Zr
, Ta, Nb+ AA, and W. Among these elements, Cr, Ni, A
L and W are preferable because they are inexpensive.

The method for forming the FexN film is F e + F 84
N*F e, N y F ex ~3NI Fa,
A using at least one powder, powder sintered body, or bulk selected from Fe such as N or its nitride as a raw material
A method of physical vapor deposition in an RFI stream, a mixed stream of Ar and nitrogen, a nitrogen stream, or a mixed stream of these and hydrogen is usually used, but this does not exclude chemical vapor deposition. As Ne.

It is also possible to use Kr and Xθ.

Methods for incorporating the above-mentioned elements such as Cr into the FexN film include mixing and melting Cr with the above-mentioned Fa or iron nitride as a raw material, or placing a chip of Or etc. on Fe or iron nitride. You can use things as raw materials.

The thickness of the FexN film containing F8XN or Cr is more preferably 0.1 to 1.0 μm. The reason why a film in this range is preferred is that a film thickness of 0.1 μm or less is difficult to form a perpendicularly magnetized film, and a film thickness of 1.0 μm or more makes recording with a magnetic head difficult.

FexN11 containing the above-mentioned FexN or Cr etc.
9! -500V to -50V with respect to earth when forming
It is more preferable to apply a bias voltage of V to the substrate because it improves the characteristics of the magnetic film.

Whether or not FaxNii is a perpendicularly magnetized film can be determined by observing the reproduced waveform (IEICE Magnetic Recording Study Group Material MR76-16゜p19).An easy way to tell is if it has high permeability magnetism. So-called 2NN with a membrane attached
When making a membrane body.

FexN@ formed on the intermediate film excluding the high permeability magnetic film
The ratio of the residual magnetic flux density in the perpendicular direction to the residual magnetic flux density in the in-plane direction of the monitor (Br (This is because the magnetic properties of perpendicularly magnetized films were difficult to measure.) Normally, if Br/Brz is 0.8 or more, it is considered to be a perpendicularly magnetized film, and in fact, the reproduced waveform by the magnetic head and Br
There was almost no difference in the simple discrimination method using □ / B r z (the upper limit of the above B' s judged from the reproduced waveform was about 300 G larger than the above Bs judged from B r , / B r #). However, it is probably not an essential difference).

[Embodiments of the invention]

EXAMPLES The present invention will be explained below with reference to Examples, but these Examples do not impose any limitations on the present invention.

Example 1 Using the RF sputtering apparatus shown in FIG. 2, permalloy (high permeability magnetic film) was deposited on a nonmagnetic substrate, and FexN was sputtered thereon through various intermediate films. Note that a shutter was placed on the monitor for measuring magnetic properties, and a film with only the permalloy removed was attached.

In Figure 2, numeral 1 is a non-magnetic substrate, which has a structure that can apply a bias voltage of -500 to Ov with respect to the ground, and a shutter is attached to the monitor section on the substrate. It has a structure that prevents permalloy from getting on the monitor. 2 is a sputter target, which has a structure that allows 13.5 MHz RF to be applied to the target, and also has a structure that allows three targets to be placed at the same time, including a high magnetic permeability film and an intermediate film.

FexN film can be sputtered continuously. 3 has a structure in which the mixing ratio of Ar, N, and H□ can be adjusted using a needle valve.

Using the above device and using a 100φ target, 5
Permalloy of about 1.0 μm was deposited on a glass substrate optically polished in Ar at X 10-” Torr, and then an intermediate metal film of O,OS μm was deposited. Next, a 100φ Fe , 10 using N compact powder target
X 10-'Torr of Ar [trace amount of N8 (0-5
voQ%) on the above interlayer film.
m of iron nitride was deposited. When depositing iron nitride, a bias of -150 V with respect to ground was applied to the substrate.

The ultimate degree of vacuum was set to I x 10-'Torr in all cases of permalloy, intermediate film, and iron nitride.

The intermediate film has M n (nearest neighbor atomic ratio ill: 2
．． 24 people).

V (2,63 people), Ru (2,65 people), 0s (2,
68 people), Rh (2,69 people), Ir (2,71 people)
, Mo (2,73 people), W (2,74 people),
Re (2,74 people), Pd (2,75 people).

Pt (2,78 people), Nb (2,86 people), T
a (2,86 people), Afl (2,86 people),
Au (2,88 people), Ag (2,89 people) + Ti (
2,89 people), Sn (3,01 people), Gd (3,56 people)
human), recently interatomic ratio @ (OCA) and FexN
FIG. 1 shows the relationship between Bs and the upper limit value at which Bs becomes a perpendicularly magnetized film. The upper limit of Bs is 2 to 3 (N: 20
~33 at%)
It was determined from Bs where z is 0.8 or more.

As is clear from Figure 1, DCA is 2.5 to 3.2.
When a human intermediate film is used, Bs, which makes the FexN film a perpendicularly magnetized film, increases rapidly. A FexN film with such a high Bs can provide a large reproduction output, and is therefore considered to be advantageous as a perpendicular magnetic recording material. OCA is 2.65
~2.85 In the human interlayer, the above-mentioned Bs value becomes even larger.

Table 1 shows that without an interlayer, in this case Permalloy is deposited very thinly < (0.05 μm), and Permalloy and Fe
(The characteristics of only the FexN film were estimated from the mixed B-H characteristics of the N film), Re, W from Table 1, Table 2, and Table 1 showing the magnetic properties of FaxN prepared with Ti as an intermediate film. As shown by Akira, even if Bs is large, the FexN film coated with an interlayer film has Br/Br, ((Br
, /Bs)/(Br, /Bs)) is 0.8 or more, making it a perpendicularly magnetized film.

In Table 1, it can be seen that there is a slight increase in Re after depositing the intermediate film, but this is thought to be related to the fact that the C-axis of FexN was oriented in the direction perpendicular to the film surface.

Example 2 SnO, (DCA 3.19 people), Ti as an intermediate film
F (3.03 people) in the same way as in Example 1.
Table 2 shows the results when an exN film was formed.

As is clear from Table 2, OCA is 2.5 to 3.2.
Even when human oxide or nitride is used, the upper limit value of Bs at which the FexN film becomes a perpendicularly magnetized film is increased compared to the case without an intermediate film.

Example 3 Using Re as an interlayer film with a thickness of 0 to 0.18 μm, Example 1 formed a FexN film containing 5 at% Cr on this interlayer film.
The reproduction output of this perpendicular recording medium was evaluated. 1.0μm Co@*Zrg for high permeability magnetic film
, JOla,s was used. Figure 3 shows the relationship between the intermediate film thickness and the reproduction output (the magnetic head was a single pole type head with a main pole film thickness of 0.3 μm, and the recording was measured at a relative speed of 2.5 m/s. Current is recording density I KPC
As is clear from Fig. 3, the thickness of the intermediate film was changed from O to 0.01.
When the thickness is increased to μm, the reproduction output increases rapidly, and when the film thickness is 0.
The reproduction output reaches its maximum at around 0.3 μm, and as the film thickness increases further, the reproduction output gradually decreases until the film thickness reaches 0.1 μm.
Above μm, the reproduction output sharply decreases as the film thickness increases. From this result, the thickness of the intermediate film is 0.01 to 0.1
It can be seen that μm is good.

Example 4 A FexN film containing 10JX% of Ru was deposited as a magnetic film in the same manner as in Example 1, using Mo with a thickness of 0.05 μm as the base film. When depositing the FexN film, a bias of 1,500 to 0 V with respect to ground was applied to the substrate. The results are shown in Table 3. As is clear from Table 3, -50
When a bias of 0 to −50 V is applied to the substrate, HQ A rB r A / B s of the FexN film increases, and Br
z/Bg decreases slightly. These are considered to be advantageous in improving frequency characteristics when the FexN film is used as a perpendicular magnetic recording medium.

Table 3 From the examples described above, the average nearest neighbor atomic distance is 2.5
~3. By using two metals, metal nitrides, and metal oxides as the interlayer film, the upper limit of Bs becomes higher, and when Bs is kept at a certain level, the FaxNll formed on the interlayer film becomes a vertical oxide film. It was found that the characteristics of the perpendicularly magnetized film improve when the value is increased. The thickness of this intermediate film is 0, judging from the playback output.
．． It has become clear that 0.01 to 0.1 μm is good.

In the above embodiments, the high permeability magnetic film, intermediate film, and FexN film were formed by high-frequency sputtering, but depending on the purpose, vapor deposition, magnetron sputtering, ion beam sputtering, carbon
VD method and electrodeposition method can also be used.

Moreover, although only examples have been shown in which one layer of intermediate film is used, two layers of intermediate films may be used depending on the purpose.

As the thin film forming substrate, in addition to the glass substrate used in the present invention, organic polymers such as polyester films and polyimide films, metal plates such as AQ, thin strips, etc. can be used. Further, the substrate may be of any shape as required, such as an elongated shape or a disk shape.

Other matters not specifically described in this specification (intermediate film for improving adhesion between the film and the substrate, and between the films).

Regarding inorganic or organic protective films, lubricating films, etc. for improving durability, already known knowledge may be applied.

〔Effect of the invention〕

As is clear from the above explanation, by using the intermediate film according to the present invention, the range of Bs in which the FexN film becomes a perpendicularly magnetized film (that is, the range of big.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between the closest interatomic distance of the intermediate film and the upper limit value of Bs at which the FexN film becomes a perpendicular magnetization film in one embodiment of the present invention, and FIG. High magnetic permeability film in one embodiment, interlayer film, l! FIG. 3, which is a schematic diagram of the high frequency sputtering apparatus used for producing the iron oxide, is an explanatory diagram showing the relationship between the intermediate film thickness and the reproduction output.

Claims (1)

[Claims] 1. A non-magnetic substrate, a high permeability magnetic material, and at least one
A perpendicular magnetic recording medium comprising a thin film magnetic material mainly composed of iron nitride having perpendicular magnetic anisotropy and deposited through an interlayer film. 2. In the perpendicular magnetic recording medium according to claim 1, the intermediate film has a distance between nearest atoms of 2.5 to 3.
2 Å, and a total thickness of the intermediate film is 0.01 to 0.1 μm. 3. In the perpendicular magnetic recording medium according to claim 1 or 2, the intermediate film is made of V, Ru, Zn, O.
s, Rh, Ir, Mo, W, Re, Pd, Pt, Nb,
A perpendicular recording medium comprising at least one selected from Ta, Sn, Al, Au, Ag, Ti, and nitrides and oxides of these elements. 4. In the perpendicular magnetic recording medium according to claim 1 or 2, the film thickness of the thin film magnetic material is 0.1 to 1.
0μm, nitrogen content 20-32 at%, saturation magnetization 2
1. A perpendicular magnetic recording medium comprising a perpendicularly magnetized film mainly made of iron nitride of 000 to 10,000 G. 5. In the perpendicular magnetic recording medium according to claim 1 or 2, the thin film magnetic material contains iron as well as Cr, N,
i, Co, Bi, platinum metal element, Zr, Ta, Nb, Al
, W, in an amount of 10 atomic % or less.