JP2752179B2 - Perpendicular magnetic recording medium and method of manufacturing the same - Google Patents

Description

The present invention relates to a perpendicular magnetic recording medium having a ferromagnetic metal thin film made of iron nitride or an iron nitride-based alloy as a magnetic layer, and a method of manufacturing the same.

(B) Conventional technology Perpendicular magnetic recording disclosed by Iwasaki et al. Of Tohoku University is a recording method that is essentially suitable for high-density recording because the self-demagnetization effect is suppressed as the recording density increases. As a medium for perpendicular magnetic recording, a Co—Cr film produced by a sputtering method or a vacuum evaporation method has been disclosed.

The Co—Cr film is large in both magnetic anisotropy and saturation magnetization and is excellent as a perpendicular recording medium. However, Co has a problem because it is expensive in cost. As a solution to the above disadvantages, an inexpensive Fe-based perpendicular magnetic recording medium based on Fe has been proposed, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-228705 (H01F10 / 18). This is hexagonal iron nitride (ε-Fe _2-3)
N) is a medium mainly composed of iron, γ′-Fe ₄ N, ε-Fe
_At least one powder selected from Fe or nitride thereof, such as _2-3 N, ζ-Fe ₂ N, a powder sintered body, and a bulk, in an Ar gas stream, a mixed gas stream of Ar and nitrogen Alternatively, it is formed by performing physical vapor deposition (sputtering method, vacuum vapor deposition method) in a mixed gas flow of Ar, nitrogen, and hydrogen.

However, in the case of the thin film magnetic material mainly composed of hexagonal iron nitride as described above, the magnetic layer cannot be formed at a high speed, and is not a magnetic recording medium suitable for mass production.

(C) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has a perpendicular magnetic recording having an iron nitride-based magnetic layer having perpendicular magnetic anisotropy that can be formed at high speed. It is an object to provide a medium and a method for manufacturing the medium.

(D) Means for Solving the Problems The perpendicular magnetic recording medium of the present invention mainly comprises a paramagnetic iron nitride ζ-Fe ₂ N on a non-magnetic substrate, and the paramagnetic iron nitride ζ-Fe
₂ N are alpha-Fe phase and γ'-Fe ₄ N phase and the phase separation of the ferro-magnetic, FeN the crystal structure has a perpendicular magnetic anisotropy is columnar structures extending in a direction perpendicular to the substrate top surface A magnetic thin film is formed by deposition.

Further, the method for manufacturing a perpendicular magnetic recording medium of the present invention includes the step of vapor-depositing iron vapor on a heated non-magnetic substrate from a direction perpendicular to the upper surface of the substrate, and containing nitrogen ions and electrons in the vapor-deposited portion. on the substrate by irradiating a nitrogen plasma, the paramagnetic iron nitride ζ-Fe ₂ N and mainly, the normally chronotropic iron nitride ζ-Fe ₂ N is ferromagnetic alpha-Fe phase and gamma prime-Fe
The FeN-based magnetic thin film having perpendicular magnetic anisotropy that is ₄ N phase and phase separation, characterized in that deposited and formed.

(E) Action In the perpendicular magnetic recording medium having the above structure, paramagnetic iron nitride
Ferromagnetic α-Fe phase and γ'-Fe with crystallization of Fe ₂ N
_A magnetic separation effect occurs in the phase separation from the 4N phase, and this synergizes with the shape anisotropy due to the fine columnar structure extending perpendicularly to the upper surface of the substrate, resulting in Fe with excellent perpendicular magnetic anisotropy.
An N-based magnetic thin film is formed.

Further, in the above-described manufacturing method, the crystallization of paramagnetic iron nitride ζ-Fe ₂ N proceeds due to the interaction between the ion irradiation in the low kinetic energy region from the plasma generation chamber and an appropriate substrate temperature.

(F) Embodiment FIG. 1 is a schematic cross-sectional view of an apparatus for manufacturing a perpendicular magnetic recording medium by an ion-assisted vapor deposition method used in this embodiment.

In the figure, (1) is 1 × 10 ^-6 To inside by exhaust system (2).
This is a vacuum chamber maintained at a high vacuum of rr or less. A crucible (3), a substrate holder (4), and a plasma generation chamber ( 5 ) are provided inside the vacuum chamber (1). The crucible (3) contains iron (6) as an evaporation source.
A non-magnetic substrate (7) is provided on the lower surface of the substrate holder (4).
Is mounted, and the crucible (3) is arranged directly below the substrate (7). Further, a heater (not shown) is mounted inside the substrate holder (4), and the temperature of the substrate (7) is controlled by the heater. The plasma generation chamber ( 5 ) has a filament (8) and an anode (9) mounted inside, and a solenoid coil (10) is wound around the peripheral surface. A current of 20 to 30 A flows through the filament (8) by a DC power supply (11a), and a DC power supply (11
According to b), a positive voltage of 100 V is applied. A porous grid (13) that is electrically grounded is attached to an opening of the plasma generation chamber ( 5 ) on the plasma (12) emission side, and the grid (13) allows the plasma generation chamber ( 5 ) There is a pressure difference between inside and outside. (14) is a gas introduction pipe for introducing nitrogen gas into the inside of the plasma generation chamber ( 5 ).

In the above-described production apparatus of the present embodiment, neutral nitrogen molecules introduced into the plasma generation chamber ( 5 ) through the gas introduction pipe (14) are released from the filament (8) and accelerated by the anode (9). It is ionized by colliding with the emitted thermoelectrons. The low-energy nitrogen ions and electrons generated by the ionization become nitrogen plasma (12), and the plasma generation chamber ( 5 ) is formed by the magnetic field scent formed by the solenoid coil (10) and the pressure difference by the grid (13). Is radially emitted to the outside from the opening. The released nitrogen plasma (12) irradiates the substrate (7) simultaneously with the iron vapor (14) from the crucible (3). Therefore, the positive charges of the nitrogen ions reaching the substrate (7) are neutralized by the electrons, and the substrate (7) does not charge up. Since the kinetic energy of the nitrogen ions and electrons is as small as 100 eV or less, the iron nitride (FeN) magnetic thin film formed on the substrate (7) does not undergo thermal dissociation.

Using the above-described manufacturing apparatus, a FeN magnetic thin film was formed on a film substrate under the following conditions.

−Deposition conditions− Back pressure 1 × 10 ⁻⁶ torr or less Nitrogen gas pressure 2 × 10 ⁻⁴ torr Deposition rate 750 to 1750Å / min Nitrogen ion current density 2.0mA / cm ² Incident angle of iron vapor 90 ° Film substrate temperature 100 ° C. Nitrogen ion kinetic energy 100 eV or less FIG. 2, FIG. 3 and FIG. 4 show the dependency of the magnetic properties of the FeN magnetic thin film formed under the above-described film forming conditions on the film forming speed.
FIG. 2 is a graph showing the dependence of the saturation magnetization Ms on the deposition rate, and the dependence of the residual magnetization ratio Br⊥ / Br ″ between the perpendicular direction and the in-plane direction on the deposition rate. FIG. 4 is a graph showing the dependency of the directional magnetic field Hk on the film forming speed, and FIG.

As can be seen from FIGS. 2, 3 and 4,
As it decreases from 1750Å / min, the remanent magnetization ratio Br⊥ / Br ″ between the perpendicular direction and the in-plane direction, and the perpendicular magnetic anisotropic magnetic field H
k, the perpendicular magnetization characteristics such as the perpendicular coercive force Hc 向上 are improved, and when the deposition rate is 1000Å / min, the saturation magnetization Ms is 290 emu / cc, and the residual magnetization ratio Br⊥ / Br ″ between the perpendicular direction and the in-plane direction is 1.2, good perpendicular magnetization characteristics with perpendicular magnetic anisotropy magnetic field Hk of 2800 Oe and perpendicular coercive force Hc⊥ of 450 Oe were obtained.

FIG. 5 is a scanning electron micrograph showing the crystal structure of the FeN magnetic thin film formed at the film forming rate of 1750 ° / min under the above-described film forming conditions, and FIG. 6 is a film forming rate of 1000 ° / min under the above-described film forming conditions. 5 is a scanning electron micrograph showing a crystal structure of a FeN magnetic thin film formed by the method of Example 1.

As can be seen from FIGS. 5 and 6, the film formation rate is 1750Å / min.
No columnar crystal structure was observed in the FeN magnetic thin film formed in step 1. A crystalline structure of the structure is formed.

FIG. 7 is a diagram showing the result of composition analysis by X-ray diffraction of a FeN magnetic thin film formed at a film forming speed of 1750 ° / min under the above film forming conditions, and FIG. 8 is a film forming speed of 1000 ° under the above film forming conditions. / min
FIG. 6 is a view showing the result of composition analysis of the FeN magnetic thin film formed by X-ray diffraction by X-ray diffraction.

As can be seen from FIGS. 7 and 8, the deposition rate is 1750Å / min.
The diffraction pattern of the FeN magnetic thin film formed by γ'-Fe ₄ N
Whereas a mixed pattern of the ferromagnetic phase of the _ε-Fe 2~3 _N, deposition rate good vertical magnetization characteristics were obtained
The FeN magnetic thin film formed by 1000 Å / min showed a diffraction pattern of only ζ-Fe ₂ N.

Fig. 9 shows a film formation rate of 1000 with good perpendicular magnetization characteristics.
FIG. 9 is a diagram showing the results of composition analysis of FeN magnetic thin films formed at Å / min by Mossbauer spectroscopy, and FIG.
The composition of the magnetic thin film was found as follows.

-FeN composition of the magnetic thin film - paramagnetic (room temperature) ζ-Fe ₂ N 62% paramagnetic (room _temperature) ε-Fe 2~3 N 22% ferromagnetic (room temperature) α-Fe 8% ferromagnetic (room temperature) gamma ' -Fe ₄ N 8% Further, it is seen that the magnetization of the FeN magnetic thin film is attributed to γ'-Fe ₄ N and alpha-Fe ferromagnetic.

In addition, when the nitrogen content of the FeN magnetic thin film formed under the above-described film forming conditions was examined by electron spectroscopy, the nitrogen content increased as the film forming speed was reduced, and good perpendicular magnetization characteristics were obtained. Nitrogen content at a deposition rate of 1000Å / min
atm%.

Next, under the above-described film forming conditions, the film forming speed was set to 1000Å / m
The substrate temperature dependence of the magnetic properties of the FeN magnetic thin film formed by fixing the substrate at in and changing the substrate temperature from 40 ° C to 240 ° C
This is shown in the figure and FIG. FIG. 10 shows the substrate temperature dependence of the saturation magnetization Ms and the substrate temperature dependence of the residual magnetization ratio Br⊥ / Br ″ between the perpendicular direction and the in-plane direction. FIG. 11 shows the perpendicular magnetic anisotropy magnetic field Hk FIG. 4 is a diagram showing the substrate temperature dependence of the present invention.

As can be seen from FIGS. 10 and 11, the perpendicular magnetization characteristics such as the perpendicular magnetization and the in-plane residual magnetization ratio Br⊥ / Br ″ and the perpendicular magnetic anisotropic magnetic field Hk are formed at a substrate temperature of around 100 ° C. The FeN magnetic thin film shows the best value.

The FeN magnetic thin film of the example formed under the conditions of the above-mentioned substrate temperature of 100 ° C. and a film formation rate of 1000 ° C./min has a ferromagnetic α of a fine columnar structure grown vertically to the upper surface of the substrate (7).
Around -Fe phase and γ'-Fe ₄ N phase crystal, the interaction with the substrate temperature of ion irradiation and 100 ° C. in the following low kinetic energy region 100eV from the plasma generation chamber (5) of paramagnetic Crystallization of ζ-Fe ₂ N causes a magnetic separation effect in the phase separation between the α-Fe phase and the γ′-Fe ₄ N phase, which synergizes with the shape anisotropy due to the fine columnar structure. Shows more excellent perpendicular magnetic anisotropy.

As a comparative example, a FeN magnetic thin film was formed on the substrate (7) using the ordinary vacuum evaporation apparatus shown in FIG. 12 under the following conditions.

−Deposition conditions− Back pressure 1 × 10 ⁻⁶ torr or less Nitrogen gas pressure 2 × 10 ⁻⁴ torr Deposition rate 1000Å / min Nitrogen ion current density 0mA / cm ² Incident angle of iron vapor 90 ° Film substrate temperature 100 ° C Nitrogen Ion kinetic energy 0 eV The following table shows the above examples (film deposition rate 1000Å / min, substrate temperature
The magnetic properties of the FeN magnetic thin film formed at 100 ° C.) and the FeN magnetic thin film formed in the above comparative example are shown.

In addition, the observation of the FeN magnetic thin film formed in the above comparative example with a scanning electron microscope does not show a crystal structure of a columnar structure, and the composition analysis by X-ray diffraction shows only a diffraction pattern of α-Fe. Was.

As another comparative example, a FeN magnetic thin film was formed on a substrate (7) by obliquely depositing iron while tilting the substrate holder (4) at a predetermined angle in the manufacturing apparatus of FIG. This FeN-based magnetic thin film has a columnar crystal structure grown obliquely above the upper surface of the substrate as shown in FIG. 13, and has a nitrogen content of
It is 16 atm%. However, the FeN magnetic thin film of this comparative example has a perpendicular magnetization and an in-plane residual magnetization ratio Br⊥ / Br ″ of about 0.30, and has almost no perpendicular magnetic anisotropy.
In the scanning electron micrographs shown in FIGS. 5, 6, and 13, the magnification is 1 cm = 1660 °.

(G) Effects of the Invention According to the present invention, it is possible to provide a perpendicular magnetic recording medium suitable for mass productivity and excellent in perpendicular magnetic anisotropy, and a method for manufacturing the same.

[Brief description of the drawings]

1 to 11 relate to the present invention, FIG. 1 is a schematic sectional view of a manufacturing apparatus, and FIGS. 2, 3, and 4 each show the dependency of the magnetic properties of a FeN magnetic thin film on the deposition rate. FIGS. 5 and 6 are scanning electron micrographs showing the crystal structure of the FeN magnetic thin film, respectively. FIGS. 7 and 8 are X-ray images of the FeN magnetic thin film, respectively.
FIG. 9 shows a Mossbauer spectrum of a FeN magnetic thin film, and FIGS. 10 and 11 show Fe diffraction, respectively.
FIG. 3 is a diagram showing the substrate temperature dependence of the magnetic properties of an N magnetic thin film. FIG. 12 is a schematic sectional view of the manufacturing apparatus, and FIG. 13 is a scanning electron micrograph showing the crystal structure of the FeN magnetic thin film. ( 5 ) Plasma generating chamber (7) Substrate (12)
... nitrogen plasma, (14) ... iron vapor.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-25204 (JP, A) JP-A-57-130405 (JP, A) JP-A-1-105331 (JP, A) JP-A-59-130 228705 (JP, A) JP-A-63-241718 (JP, A)

Claims (2)

(57) [Claims] A paramagnetic iron nitride 、 -Fe ₂ N is formed on a non-magnetic substrate.
And the paramagnetic iron nitride ζ-Fe ₂ N is ferromagnetic α
-Fe phase and gamma prime-Fe ₄ are N-phase and phase separation, deposited and formed a FeN-based magnetic thin film having perpendicular magnetic anisotropy is columnar structures extending in the vertical direction crystal structure to the substrate top surface A perpendicular magnetic recording medium characterized in that: 2. The method according to claim 1, further comprising: evaporating iron vapor on the heated non-magnetic substrate from a direction perpendicular to the upper surface of the substrate; and irradiating the vapor deposition section with nitrogen plasma containing nitrogen ions and electrons. Above, the main component is paramagnetic iron nitride ζ-Fe ₂ N, and the normal iron nitride ζ-Fe ₂ N is ferromagnetic α-
A method of manufacturing a perpendicular magnetic recording medium characterized by the FeN-based magnetic thin film having perpendicular magnetic anisotropy that is Fe phase and gamma prime-Fe ₄ N phase and the phase separation be deposited and formed.