JPH0679369B2 - Magnetic recording material and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an Fe-based magnetic recording material having excellent corrosion resistance and magnetic properties, and a method for producing the same.

[Technical background of the invention and its problems]

In recent years, the demand for high-density magnetic recording is increasing,
In response to this, a thin film type magnetic recording material has been developed in which a thin film made of a ferromagnetic metal is deposited on a non-magnetic substrate by a method such as sputtering or ion plating. Among them, a magnetic recording material obtained by depositing a Co-based magnetic material as a thin film on a base material by an oblique evaporation method has excellent magnetic characteristics and is therefore used for, for example, a microcassette tape.

However, the Co-based magnetic recording material has a high material cost, and since the recording material is produced by the oblique vapor deposition method and the vapor deposition efficiency is low, the magnetic recording material has a disadvantage of being too expensive. The use of other inexpensive magnetic materials has been desired.

On the other hand, the Fe-based magnetic recording material formed by using the Fe-based magnetic material may have a large reduction in price because of its low material cost, but it has insufficient corrosion resistance and There is a problem that a high coercive force cannot be obtained, and the fact is that it has not been put to practical use despite various attempts made in the past.

The present inventors have found the following facts as a result of earnest research to solve the problems associated with the above Fe-based magnetic materials.

(A) When a Fe-based magnetic material is formed on a substrate by a method such as ion plating or sputtering in a nitrogen-containing gas such as N ₂ or NH ₃ , iron nitride such as Fe ₄ N or Fe ₈ N is formed. A Fe-based thin film containing Fe should be obtained.

(B) The Fe-based thin film containing iron nitride is compared with the Fe-based thin film containing no iron nitride formed on the substrate by vacuum deposition of Fe in an inert gas such as argon. Greatly improved corrosion resistance.

(C) When depositing a Fe-based magnetic material on a substrate by a method such as ion plating or sputtering, determine the angle between the perpendicular line standing on the substrate surface and the Fe-based vapor stream, that is, the incident angle. The coercive force Hc of the obtained Fe-based thin film is increased by adopting the evaporative vapor deposition method at 20 degrees, preferably 45 degrees or more, and it can be used as a magnetic recording material.

(D) When the above Fe-based magnetic recording material is formed on the substrate, the composition of the obtained Fe-based thin film changes significantly depending on the pressure of the nitrogen-containing gas such as N ₂ and NH ₃ , and accordingly Its magnetic properties also change significantly.

[Object of Invention and Outline thereof]

The present invention has been completed based on the above findings, and is an Fe-based thin film, but also has an Fe-based magnetic recording material having excellent corrosion resistance and excellent magnetic properties and its production. It is intended to provide a way.

The magnetic recording material according to the present invention comprises a substrate and an Fe-based thin film deposited on the substrate by orthorhombic reactive ion plating or reactive sputtering. x is 2 to 8), and the amount of iron nitride represented by Fe _{2 to 3} N is 50% or less. There is.

Further, the method for producing a magnetic recording material according to the present invention uses the Fe or Fe-based alloy as a vapor deposition source or a target in a chamber by a reactive ion plating method or a reactive sputtering method under the following conditions (a) to ( c) Under
5% of iron nitride represented by FexN (where x is 2 to 8)
The amount of iron nitride represented by Fe _{2 to 3} N is 50 or more.
The Fe-based thin film whose content is less than or equal to 5% is deposited on the substrate.

(A) When the Fe-based thin film is deposited on the substrate by the reactive ion plating method, the angle formed by the perpendicular line standing on the substrate surface and the Fe-based vapor flow, that is, the angle of incidence is preferably 20 degrees. 45
Keeping the temperature above a certain level and depositing a Fe-based thin film on the substrate.

(B) The nitrogen-containing gas pressure in the chamber is in the range of 1 × 1 ^{−4 to} 1.0 × 10 ⁻³ Torr in the case of the reactive ion plating method, and 1 × 10 ^{− in} the case of the reactive sputtering method. ³
Keep in the range of ~ 1 x 10 ^-1 Torr.

(C) Keep the deposition rate of the Fe-based thin film within the range of 1 to 200 Å / sec.

[Specific Description of the Invention]

 The present invention will be described below with reference to the drawings.

A magnetic recording material 1 according to the present invention includes a base material 2 and the base material 2.
Fe-based thin film 3 deposited on top.

Fe-based thin film 3, FeXN (x in the formula is 2 to 8) with an iron nitride 5% or more represented, preferably 20% or more, more preferably comprises at least 50%, yet Fe _{2 to 3 N} The amount of iron nitride shown is preferably 50% or less.

In the Fe-based thin film 3, in addition to the above iron nitride,
Pure iron (α-Fe) is also included, and this amount is generally 5-50.
% Is preferable.

When the amount of iron nitride represented by FexN (x is 2 to 8) in the Fe-based thin film 3 is less than 5%, the resulting magnetic recording material has insufficient corrosion resistance, which is not preferable. Also Fe
_When the amount of iron nitride represented by _{2 to 3} N exceeds 50%, the coercive force Hc and the saturation magnetization αs of the magnetic recording material sharply decrease, which is not preferable.

The amount of iron nitride represented by FexN in the Fe-based thin film 3 is
When it is 5 to 20%, it has corrosion resistance to the extent that no corrosion is observed even if it is left in a room at 40 ° C and humidity of 90% for 1 week, and the amount of iron nitride is 20 to 20%. When it is 50%, it has corrosion resistance to the extent that no corrosion is observed even if it is contacted with water containing NaCl for 1 week, and when the amount of iron nitride is 50% or more, It has corrosion resistance to the extent that no corrosion is observed even when immersed in a 5% NaCl aqueous solution for 1 week.

Although not wishing to be bound by theory, iron nitrides represented by Fe _{2 to 3} N do not have magnetism, whereas iron nitrides represented by Fe _{4 to 8} N and pure iron have magnetism. It is believed that Therefore, in the magnetic recording material according to the present invention, iron nitride represented by FexN (x is 2 to 8) is 5%.
The inclusion of the above gives corrosion resistance, and Fe
It is presumed that the reduction of the coercive force Hc and the saturation magnetization σs may be suppressed by setting the amount of iron nitride represented by _2-3 N to 50% or less. Regarding the coercive force Hc, the coercive force Hc increases rather by including a small amount of Fe ₂ to ₃ N in the Fe-based thin film, but the coercive force abruptly increases when the amount of Fe _{2 to 3} N exceeds 50%. It has been found to decrease. Non-magnetic iron nitride ( _Fe2-3N ) in such Fe-based thin films
FIG. 2 shows the relationship between the content ratio of S, the saturation magnetization σs, and the coercive force Hc.

The base material 2 is a film or sheet of synthetic resin such as polyethylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyethylene terephthalate, polyimide, polycarbonate, polyamide, non-magnetic metal such as aluminum foil, non-magnetic nickel foil, and stainless steel foil. Conventionally known materials such as the foil or sheet, glass, and ceramic plate can be widely used.

Next, a method of forming the Fe-based magnetic recording material 1 according to the present invention will be described.

The Fe-based magnetic recording material 1 according to the present invention is formed by depositing a Fe-based thin film 3 on a base material 2. However, a conventional ion plating apparatus or sputtering apparatus is used, and argon or the like is used in the apparatus. Nitrogen-containing gas such as nitrogen or ammonia is introduced instead of the inert gas of Fe, and Fe or Fe-based alloy is used as a vapor deposition source or target to deposit Fe-based thin film on the substrate by reactive ion plating or reactive sputtering. It can be attached to.

Alternatively, an ion plating device as shown in FIG. 3 may be used. The ion plating device 4 has a vacuum line 5 having a valve 6 at the bottom and a nitrogen-containing gas introduction line 7 having a valve 8 at the side. Inside the ion plating device 4, that is, in the lower part of the chamber 9, there is provided a crucible 11 for containing a target Fe or an Fe-based alloy 10. An electron gun or a resistance heating device is provided under the crucible 11. An electron beam heating device 12 including the above is provided. Further, an ionization electrode 13 and a filament 14 are provided in a position substantially horizontal to the gas introduction line 7 in the chamber 9 and above the crucible 11. Further, a holder 15 is provided almost directly above the ionization electrode 13 in the chamber 9 so that the holder 15 can hold the base material 2 to which the corrosion resistant thin film is attached by tilting. There is. That is, the holder 15 can hold the base material 2 in a tilted manner so that the angle α formed by the perpendicular line standing on the base material 2 and the Fe-based vapor flow, that is, the incident angle α can be maintained at 20 degrees, preferably 45 degrees or more. It is like this.

In such an ion plating apparatus, the Fe or Fe-based alloy 10 in the crucible 11 is the electron beam heating apparatus 12
It is heated by the electron beam 16 which is emitted from and accelerated and focused, and a vapor flow 17 of Fe or Fe-based alloy is generated upward. On the other hand, the ionization electrode 13 has a filament 14
Biased at a positive potential with respect to the ionization electrode 13, a thermoelectron flow 18 is generated between the ionization electrode 13 and the filament 14 from the filament 14 toward the ionization electrode 13. Also,
From the nitrogen-containing gas introduction line 7, the nitrogen-containing gas 19
Are introduced into the chamber 9. The vapor flow 17 of Fe or Fe-based alloy and the nitrogen-containing gas 19 are the above-mentioned thermionic flow 18
The vapor flow of Fe or Fe-based alloy is generated by collision with
And the nitrogen-containing gas 19 react with each other, and part of Fe or the Fe-based alloy becomes iron nitride, which is deposited on the base material 2.

Explaining the procedure and conditions of the above operation, first, the inside of the chamber 9 is evacuated to a high vacuum of about 10 ⁻⁶ Torr. Next, the nitrogen-containing gas 19 is fed through the gas introduction line 6 for several tens of Torr.
And the chamber 9 is filled with nitrogen-containing gas, and the flow rate of the nitrogen-containing gas is controlled by the valve 8 to evacuate again to adjust the pressure of the nitrogen-containing gas in the chamber to 1 × 10 ^{−4 to} 1.0 × 10 ^4. Keep in the ^-3 Torr range. The nitrogen-containing gas pressure in the chamber 9 has a great influence on the composition and amount of iron nitride in the obtained Fe-based thin film. When the pressure of nitrogen-containing gas in the chamber is less than 1 × 10 ⁻⁴ Torr, the production of iron nitride is insufficient and a thin film excellent in corrosion resistance cannot be obtained, which is not preferable. Also, the nitrogen-containing gas pressure is 1.0 × 10 ^-3 T
If it exceeds orr, the amount of non-magnetic iron nitride such as Fe ₂ N and Fe ₃ N will be 5
It is not preferable because the magnetic properties of the Fe-based thin film obtained by forming over 0% deteriorate.

The amount of the electron beam 16 applied to the Fe or Fe-based alloy 10 in the crucible 11 is controlled by the electric power applied to the electron beam heating device 12 including an electron gun,
Depending on the electric power applied to this electron beam heating device 12, Fe
The deposition rate of the system thin film is determined. The deposition rate of Fe-based thin film is
It is preferable to keep it in the range of 1.0 to 200Å / sec. The deposition rate also has a large effect on the composition and amount of iron nitride in the obtained Fe-based thin film, and this deposition rate is 200 Å / sec.
If it exceeds, nitriding of Fe or an Fe-based alloy cannot be sufficiently performed, which is not preferable. If the film formation rate is less than 1.0Å / sec, the film formation is not stabilized, which is not preferable.

As described above, a voltage is applied to the filament 14 to generate a thermionic flow 18, and this applied voltage varies depending on the size of the filament 14, but generally it is sufficient to heat the filament 14 to the extent that it emits white light. is there. At this time, one end of the filament 14 is preferably grounded. Further, the voltage applied to the ion electrode 13 is preferably about several tens V to the filament 14 in order to keep the ionization state of the vapor flow 17 of Fe or Fe-based alloy and the nitrogen-containing gas 19 in good condition.

In general, the crucible 11 and the holder 15 are preferably grounded, but the holder 15 may be applied with a negative voltage with respect to the ground.

As the Fe-based alloy that is a vapor deposition source, alloys mainly composed of Fe, such as Fe-Ni, Fe-Co, Fe-Ni-Co, Fe-Rh, Fe-Cr,
Fe-based strong magnetic materials such as Fe-Sm, Fe-Cr, and Fe-Si can be used.

On the other hand, in order to deposit the Fe-based thin film 1 on the substrate 2 by the sputtering method, the pressure in the chamber should be 1 × 10 ⁻³ to 1 × 10 5.
It is preferable to keep the film formation rate in the range of ^-1 Torr and the film formation rate of 0.1 to 200Å / sec.

As the nitrogen-containing gas, nitrogen gas, ammonia gas, a mixture thereof, or a mixture of these gases and an inert gas such as helium, neon or argon is used, and nitrogen gas is particularly preferable.

The film thickness of the Fe-based thin film 3 can vary over a wide range,
Generally, it is desirable to be 500 to 5000Å, preferably 500 to 3000Å.

In the present specification, the% of iron nitride in the Fe-based thin film is a value determined based on the Mossbauer method.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A polyimide film having a thickness of 50 μm was used as a base material, and an Fe-based thin film was formed on the surface of the polyimide film under the following conditions by using the ion plating apparatus shown in FIG.

Comparative Example 1 In Example 1, the vacuum degree was 5 × 10 ⁻⁵ without introducing N ₂ gas.
An Fe metal thin film was formed in the same manner as in Example 1 except that the temperature was maintained at Torr.

The composition and corrosion resistance of the Fe-based metal thin films obtained in Example 1 and Comparative Example 1 are shown in the table. The composition of the film was analyzed by Mossbauer spectroscopy.

Example 2 The same as Example 1 except that the vacuum degree was maintained at 4 × 10 ⁻⁴ Torr, 6 × 10 ⁻⁴ Torr, and 8 × 10 ⁻⁴ Torr while introducing N ₂ gas. To form a Fe-based metal thin film. The Fe _{2 to 3} N contents in the obtained Fe-based metal thin film were 25%, 25%, and 47%, respectively. No corrosion was observed at all even when left in a 5% NaCl aqueous solution for 4 days.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a magnetic recording material according to the present invention, and FIG. 2 is a content ratio of non-magnetic iron nitride (Fe _{2 to 3} N) in a Fe-based thin film constituting the magnetic recording material and saturation. FIG. 3 is a diagram showing the relationship between the magnetization σs and the coercive force Hc, and FIG. 3 is a cross-sectional view of an ion plating device used when forming an Fe-based thin film. 1 ... Magnetic recording material, 2 ... Substrate, 3 ... Fe-based thin film, 4
…… Ion plating device.

Claims (5)

[Claims] 1. A base material and Fe formed by depositing a vapor deposition material on the base material obliquely with respect to the normal line of the base material.
A magnetic recording material comprising a Fe-based thin film, wherein the Fe-based thin film contains 5% or more of iron nitride represented by FexN (x is 2 to 8), and Fe _{2 to 3} N Characterized in that the amount of iron nitride is 20 to 50%,
Magnetic recording material. 2. FexN (where x is 2 to 8 in the formula) under the following conditions (a) to (c) by a reactive ion plating method using Fe or an Fe-based alloy as a vapor deposition source in a chamber. ) Containing 5% or more of iron nitride, and Fe _{2 to 3}
An Fe-based thin film in which the amount of iron nitride represented by N is 20 to 50%,
A method for producing a magnetic recording material, which is characterized in that the magnetic recording material is deposited on a base material: (a) An angle formed by a perpendicular line standing on the surface of the base material and an Fe-based vapor flow, that is, an incident angle is kept at 20 degrees or more, Depositing a Fe-based thin film on the substrate, (b) the pressure of the nitrogen-containing gas in the chamber is 1 × 10 ^-4 ~
Keeping in the range of 1.0 × 10 ^-3 Torr, (c) Keeping the deposition rate of Fe-based thin film in the range of 1 to 200 Å / sec. 3. The method for producing a magnetic recording material according to claim 2, wherein the nitrogen-containing gas is nitrogen gas, ammonia gas, a mixture thereof, or a mixture thereof with helium, neon or argon. 4. FexN (where x is 2 to 8) under the following conditions (a) and (b) by a reactive sputtering method using Fe or an Fe-based alloy as a target in a chamber.
A Fe-based thin film containing 5% or more of iron nitride represented by and having an iron nitride content of 20 to 50% represented by Fe _{2 to 3} N deposited on a substrate. Manufacturing method of recording material: (a) The pressure of the nitrogen-containing gas in the chamber is set to 1 × 10 ⁻³ or more.
Keeping in the range of 1.0 × 10 ^-1 Torr, (b) Keeping the deposition rate of Fe-based thin film in the range of 0.5 to 200Å / sec. 5. The method for producing a magnetic recording material according to claim 4, wherein the nitrogen-containing gas is nitrogen gas, ammonia gas, a mixture thereof, or a mixture thereof with helium, neon or argon.