JPH0313731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic disks.

2. Prior Art Conventionally, this type of magnetic recording medium has been widely used for recording various electrical signals such as video, audio, and digital signals. These have been developed as a system that uses magnetization in the in-plane longitudinal direction of a magnetic layer (magnetic recording layer) formed on a substrate. The magnetic layer of these known magnetic recording media contains γ-
It contains magnetic substances such as iron oxide ferromagnetic powder such as Fe ₂ O ₃ and metal magnetic powder such as Co-containing Fe. or,
Perpendicular magnetic recording systems are also being considered for higher density.

3. Purpose of the Invention The purpose of the present invention is to provide a method for manufacturing a magnetic recording medium having a magnetic layer with high coercive force, high magnetization, and high corrosion resistance, using a magnetic material having a composition and structure completely different from known magnetic materials. There is a particular thing.

4. Structure of the Invention That is, in the present invention, a pair of targets containing iron as a main component are made to face each other, and nitrogen gas is supplied between these opposing targets so that the nitrogen partial pressure is 10 ^-3 Torr.
After generating iron nitride ions in a plasma atmosphere and accelerating the iron nitride ions in an accelerating electric field, the iron nitride ions are placed on a target on the side where the ions exit to the outside of the sputtering part and on a screen grid placed near the outside of the target. These targets and grids are each held at a predetermined potential, and a small hole is formed in these targets and grids to allow the ionized particles to pass through. Deriving iron nitride ions, guiding the derived iron nitride ions onto the substrate,
The present invention relates to a method of manufacturing a magnetic recording medium, characterized in that a magnetic layer containing as a main component amorphous iron nitride with Hc of 400 Oe or more and 600 Oe or less is formed.

Amorphous iron nitride (Fe _1-x
Nx) is in an amorphous state with no phase separation (that is, a single phase and no grain boundaries) in its structure, and as described later, it satisfies the required performance as a magnetic material. Satisfied. From this point of view, the composition of the above Fe _1-x Nx is
It is desirable that ≧0.4, and when x<0.4, the amount of nitrogen tends to be small and it becomes difficult to form amorphous amorphous.

5 Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of the magnetic recording medium according to this example will be explained.

The magnetic recording medium shown in FIG. 1 consists of a substrate S (for example, aluminum, polyethylene terephthalate, etc.) provided with a magnetic recording layer 14 containing the above-mentioned amorphous Fe _1-x Nx as a main component. Here, "main component" means that Fe _1-x Nx is substantially 100%
In addition to the case where the
Al, Ti, V, Cr, Mn, Cu, W, Pt, Zr, Nb,
metals such as Mo, nonmetals such as F, Ne, P, S, As, Se, semimetals such as C, Si, Ge, etc.)
This means that it may also include. Above Fe _1-x Nx
It is particularly good that x≧0.4, for example, Fe ₆₀ N ₄₀ ~
It consists of Fe ₅₀ N ₅₀ (x=0.4-0.5). this
Fe _1-x Nx is amorphous iron nitride with no phase separation, and has a coercive force (Hc) of 600, which is sufficient for magnetic recording.
~400 Oe, and high saturation magnetization (e.g.
12KGauss). Moreover, Fe _1-x
Nx also has excellent corrosion resistance due to the nitrogen content.

FIG. 2 shows another magnetic recording medium, for example, a magnetic disk, in which a magnetic film 14 made of the amorphous Fe _1-x Nx described above is provided on the front and back sides of a substrate S.

Next, a method of manufacturing the above magnetic recording medium will be explained with reference to FIGS. 3 to 8.

The apparatus shown in FIG. 3 basically consists of a facing target sputter section A and an ion beam extraction section B that extracts ionized particles from this sputter section.

In the sputter section A, 1 is a vacuum chamber, and 2 is a gas introduction pipe for introducing a predetermined gas (Ar+N ₂ ) into the vacuum chamber 1 and setting the gas pressure to about 10 ^-3 to ^{10 -4} Torr. The exhaust system of the vacuum chamber 1 is not shown. The target electrode is held by the target holder 4.
It is constructed as a facing target electrode in which a pair of Fe targets T ₁ and T ₂ are placed facing each other in parallel with each other. A magnetic field is formed between these targets by external magnetic field generating means (magnetic coil) 3. In the figure, 5 is a cooling water inlet pipe, 6 is a cooling water outlet pipe, and 13 is an acceleration electrode.

In the sputtering device configured in this way,
A magnetic field is formed in a direction perpendicular to the surfaces of both targets T ₁ and T ₂ facing each other in parallel, and this magnetic field creates a gap between the cathode fall area (i.e., between targets T ₁ and T ₂ as clearly shown in FIG. 4). Between the generated plasma atmosphere 7 and each target _T1 and _T2 , the γ electrons emitted by the impact of the sputtering gas ions accelerated by the electric field on the target surface are transferred to the space between the targets. Lock it in and move it towards the other target. The γ electrons that have moved to the other target surface are reflected by the cathode fall section nearby. Thus, the γ electrons reach the target T ₁ −T ₂
In between, the reciprocating motion is repeated while being constrained by a magnetic field. During this reciprocating motion, the γ electrons collide with the neutral atmospheric gas to generate ions and electrons of the atmospheric gas, and these products promote the release of γ electrons from the target and the ionization of the atmospheric gas. . Therefore, a high-density plasma is formed in the space between the targets _T1 and _T2 , and the target material is sputtered sufficiently.

Compared to other flying methods, this facing target sputtering device enables film formation at a high deposition rate using high-speed sputtering, and the substrate is not directly exposed to plasma, allowing film formation at low substrate temperatures. is possible.

The structure of the device shown in Fig. 3 that should be noted is that the Fe ejected from the target in the spatter section A
It has a derivation part B for efficiently deriving to the outside the particles ionized by the reaction between the reactant gas (N 2 ) and the reaction gas (N ₂ ), that is, Fe _1-x Nx ions.
That is, this derivation part B has a screen grid G arranged near the outside of the target T ₂ , and the target T ₂ and the grid G are each held at a predetermined potential, and at the same time, the ionized particles 10 are Small holes 11 and 12 for passage are formed in corresponding numbers and patterns, respectively. This is the fifth
These are clearly shown in Fig. 6 and Fig. 6, respectively. Each small hole 11, 12
For example, the grids G may have a diameter of 2 mm and be formed at intervals of 5 mm, and the thickness of the grid G may be 1 mm.

FIG. 7 schematically shows an electric circuit system for operating the above device.
With Vp applied, a negative voltage Vt is applied to both targets T ₁ and T ₂ , and grid G is grounded.
Further, the substrate S disposed on the side of the ion beam deriving section B is also grounded. FIG. 8 shows the potential distribution of each part, where Vp is set to 0 to 200V and Vt is set to 500 to 1000V.

When the above apparatus is operated under these conditions, ions in the plasma generated in the sputter section A (vacuum level 10 ^-4 Torr or less) are accelerated at the cathode fall section 9 (see Fig. 4) of the lower target _T2 . 13, the target T ₂ -grid G
The small hole 11, while being decelerated by the electric field between
12, and is led out with energy corresponding to the potential difference between the substrate S and the plasma. The derived ion beam 10 is transported to the deriving section B (degree of vacuum).
It is effectively focused by the action of an electric field E (see FIG. 3) which is formed at a magnitude of 10 ^-5 Torr or more, and the light is incident on the substrate S with the above-mentioned energy. In this way, by changing the anode voltage Vp applied to the accelerating electrode (or anode) 13, the energy of the ions (Fe _1-x Nx) deposited on the substrate S is controlled, and the ion beam 1 is efficiently controlled by the action of the grid G.
0 can be extracted and guided onto the substrate S. Furthermore, since the side on which the substrate S is located is drawn to a high vacuum of 10 ^-5 Torr or more, a clean magnetic film with few impurities can be deposited.

Note that it is better not to make the small holes 11 and 12 of the target T ₂ and the grid G arranged on the side from which the ion beam is extracted more than necessary, but if they are made too large, the difference in gas pressure between the sputter section A and the extraction section B may cause As a result, unnecessary gas leaks to the substrate S side, which tends to cause a decrease in the purity of the deposited film, which is also undesirable in terms of the strength of the target T ₂ and the grid G, and furthermore, the target area decreases and the sputtering efficiency tends to decrease. is possible.

By using the method and apparatus described above, for example, as shown in FIG.
It is possible to create a magnetic recording medium such as a magnetic tape or a magnetic disk having the Fe _1-x Nx magnetic film 14. This magnetic recording medium has a magnetic film 14 suitable for particularly high-density in-plane longitudinal magnetic recording or perpendicular magnetic recording.

Next, the above magnetized film (Fe _1-x Nx) will be described in more detail based on experimental results.

(A) Structure of Fe _1-x Nx film The formed films were all amorphous, and the structure changed depending on the nitrogen gas mixture ratio, substrate temperature (Ts), and ion acceleration voltage (Vp).

In Figure 9, total pressure Ptotal=5×10 ^-4 Torr, Vp=
The crystal structure of the film produced under 20V (constant) conditions,
The relationship between P _N2 and Ts is shown (however, the substrate is a (111) Si substrate). When Ts=200℃, the crystal phase formed is P _N2
As the value increases, a mixed phase of α−Fe and γ′−Fe ₄ N →
γ′−Fe ₄ N single phase→ε−Fe ₃ N and ζ−Fe ₂ N mixed phase→
ζ−Fe ₂ N, and the degree of nitridation of the film increases.
In addition, the _interplanar spacing is
An unknown crystalline phase (UK) with 1.9-2.0 Å was present. When Ts rises above 200°C, the boundaries between each region move toward the high P _N2 side. Even when Ts is below 200°C, there is a tendency for the degree of nitridation of the film to decrease as Ts decreases; Ts = 80°C, P _N2 4 × 10 ^-5 Torr
In this case, only the α-Fe phase was formed.

(B) Saturation magnetization of Fe _1-x Nx film The saturation magnetization (4πMs) of the film was measured using a magnetic balance.

In Figure 10, Ptotal=5×10 ^-5 Torr, Vp=20V
P _N2 and 4πMs of the film prepared under (constant) conditions
Shows Ts dependence. 4πMs is the crystal structure of the film, the structure is α
In the mixed phase case of −Fe+γ′−Fe ₄ N+U.K. (Unknown) and in the region of single γ′ phase, 4πMs of pure iron
(21.6KG), and the value is particularly high near the boundary between the two areas, approximately 25KG.
This high 4πMs can be attributed to the γ′ phase and UK phase.

However, as shown in Figure 10, as the nitrogen partial pressure P _N2 increases, the coercive force (Hc) further increases,
600 to 400 Oe, which is sufficient for magnetic recording (e.g.
500Oe) was found to be obtainable. At the same time, the saturation magnetization (4πMs) decreases once with the amount of _N2 , but increases again when P _N2 is further increased.
It was also found that a desirable value of 12 KGauss or higher could be obtained. This is considered to be because as P _N2 increases (total pressure increases), the proportion of ions in the deposited particles increases, and the crystallinity of the deposited film that is formed decreases, making it amorphous.

FIG. 11 shows a hysteresis curve (measured with a known sample vibrating magnetometer) of the above amorphous Fe _1-x Nx, and it can be seen that it has characteristics suitable for magnetic recording.

Further, the Fe _1-x Nx film described above has sufficient corrosion resistance due to the nitrogen content, and is excellent in this respect as well.

Note that the above-described example can be modified in various ways.

For example, in FIG. 3, a plurality of grids G can be set to control the ion beam in various ways.

6. Effects of the Invention As described above, the present invention includes a pair of targets whose main component is iron, which are opposed to each other, and nitrogen gas is supplied between these opposing targets to increase the nitrogen partial pressure.
Iron nitride ions were generated in a plasma atmosphere at 10 ^-3 Torr, and after accelerating the iron nitride ions in an accelerating electric field, each was held at a predetermined potential to form a small hole through which ionized particles could pass. The iron nitride ions are led out of the sputter part from the lead-out part consisting of the target and the grid to form a magnetic layer mainly containing amorphous iron nitride with an Hc of 400 Oersteds or more and 600 Oersteds or less. High Hc peculiar to iron nitride,
A high-performance magnetic recording medium exhibiting high magnetization and corrosion resistance can be provided.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIGS. 1 and 2 are cross-sectional views of two examples of magnetic recording media,
Fig. 3 is a cross-sectional view of the ion beam generator, Fig. 4 is a principle diagram of opposed target sputtering, Fig. 5 is a plan view of the target and grid on the ion beam extraction side, and Fig. 6 is the X-- An X-ray cross-sectional view, Figure 7 shows the electric circuit system of the above device, Figure 8 shows the potential distribution of each part, and Figure 9 shows the relationship between the crystal structure of the deposited film, nitrogen partial pressure, and substrate temperature. Figure, 1st
FIG. 0 is a graph showing the relationship between the saturation magnetization and coercive force of the deposited film and nitrogen partial pressure, and FIG. 11 is a hysteresis curve diagram of the deposited film. In addition, in the symbols shown in the drawings, 2...Gas introduction tube, 3...Magnetic coil, 10...Ion beam, 11, 12...Small hole, 13...Anode (acceleration electrode), 14...Magnetic (chemical) membrane, T ₁ , T ₂ ...
...Target, G...Screen grid, A...
...Spatter part, B...Ion beam extraction part, S...
...substrate (substrate).

Claims (1)

[Claims] 1 A pair of targets containing iron as a main component are made to face each other, and nitrogen gas is supplied between these opposing targets to create a nitrogen partial pressure of 10 ^-3 Torr to generate iron nitride ions in a plasma atmosphere. After ions are accelerated by an accelerating electric field, the ions have a target on the side where the ions exit to the outside of the sputtering part and a screen grid placed near the outside of the target, and these targets and grids are each set to a predetermined potential. The iron nitride ions are led out of the sputtering part from the lead-out part where small holes are formed in these targets and grids for allowing the retained ionized particles to pass through, and the led-out iron nitride ions are deposited on the substrate. A method for manufacturing a magnetic recording medium, comprising: forming a magnetic layer containing as a main component amorphous iron nitride having an Hc of 400 Oersteds or more and 600 Oersteds or less.