JPH04259204A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the manufacture of a magnetic recording medium improving the crystal orientation of a ferromagnetic metallic oxide group magnetic thin-film and enhancing the characteristics of recording/reproduction efficiency. CONSTITUTION:When a ferromagnetic metal 9 is flown onto a non-magnetic substrate 14 through an evaporation method in an oxygen 20 atmosphere and a magnetic thin-film 50 composed of a ferromagnetic metallic oxide is formed, the upper section of the non-magnetic base body 14 is irradiated with oxygen ions 18.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a perpendicular magnetic recording medium whose recording layer is a magnetic thin film made of a ferromagnetic metal oxide.

0002

2. Description of the Related Art The perpendicular magnetic recording method announced by Professor Iwasaki of Tohoku University and others is essentially a recording method suitable for high-density recording because self-demagnetization is suppressed as the recording density increases. As a recording medium for perpendicular magnetic recording, a magnetic recording medium in which a magnetic thin film made of a ferromagnetic metal or a ferromagnetic metal oxide is formed on a nonmagnetic substrate by a vacuum evaporation method is being developed. As such a recording medium, C
A recording layer using an o-Cr or Co-O magnetic thin film is known.

For example, a method for manufacturing a Co--O based magnetic thin film is described in the Journal of The Magnetic
s Society of Japan Vol. 13
, Supplement, No. S1 (1989), P
819 to P823, Co is deposited on a nonmagnetic substrate by electron beam evaporation in an oxygen atmosphere to produce a Co-O magnetic thin film, and then this magnetic thin film is heat-treated. A method is proposed.

[0004] However, in the method of manufacturing a magnetic recording medium as described above, the crystals of the magnetic thin film are not made finer and the crystal orientation is poor, resulting in poor recording and reproducing characteristics.

[0005] Furthermore, since high temperatures are generated during and after the formation of the magnetic thin film, the non-magnetic substrate must have excellent heat resistance, which poses the problem of high costs. .

[0006] In order to solve such problems, for example, in a method for manufacturing a Co--Cr based magnetic thin film,
As disclosed in Publication No. 208730 (G11B 5/85), etc., a Co-Cr based magnetic thin film is formed on a non-magnetic substrate using a vacuum evaporation apparatus, and Ar is accelerated only at the initial stage of formation of the magnetic thin film. A method has been proposed in which a magnetic recording medium is manufactured by irradiating a magnetic thin film forming portion with ions.

However, even with the method of manufacturing a magnetic recording medium as described above, the crystals of the magnetic thin film cannot be made sufficiently fine.
Due to poor crystal orientation, recording and reproducing characteristics were poor.

[0008] Furthermore, there is a risk that Ar may remain in the magnetic thin film and cause the magnetic thin film to deteriorate.

[0009]

SUMMARY OF THE INVENTION The present invention has been devised in view of the drawbacks of the conventional examples described above, and it is an object of the present invention to produce a perpendicular magnetic recording medium having excellent recording and reproducing characteristics from a long wavelength region to a short wavelength region by forming it at a low temperature. The purpose is to provide a manufacturing method that can

0010

[Means for Solving the Problems] The present invention is such that when a magnetic thin film is formed, ions of constituents of the magnetic thin film are irradiated. In particular, it is characterized in that the ions of the constituents are oxygen ions.

[0011]

[Effect] To create a magnetic thin film made of ferromagnetic metal oxide, the magnetic thin film is formed by irradiation with ions, which are the constituents of the magnetic thin film, so the crystals in the magnetic thin film are miniaturized. Crystal orientation improves.

0012

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

The magnetic tape for perpendicular magnetic recording of this embodiment has a ferromagnetic metal oxide Co- A magnetic thin film made of an O-based magnetic thin film is formed.

FIG. 1 is a schematic cross-sectional view of an apparatus for manufacturing the magnetic tape using the ion-assisted vapor deposition method used in this embodiment.

In the figure, 1 has an internal area of 5×10 due to the exhaust system 2.
It is a vacuum chamber maintained at a high vacuum of −6 Torr or less, and inside the vacuum chamber 1 there is a crucible 3, a cooling roller 4, a delivery roller 5, a winding roller 6, and an end-hole type ion source 7.
and electron guns 8 are arranged.

[0016] Inside the crucible 3 is an evaporation source having a purity of 99%.
．． A ferromagnetic metal 9 made of 9% Co is housed. The electron gun 8 irradiates the ferromagnetic metal 9 in the crucible 3 with an electron beam to melt the ferromagnetic metal 9 and generate Co vapor 19.

The ion source 7 has a filament 10 inside.
and an anode electrode 11 are attached. The filament 10 is powered by an AC power source (not shown) of 10 to 15 A.
A current of 1 is flowing through the anode 11, and a DC power source 1
2, a positive voltage of 100V is applied.

Reference numeral 13 denotes a first gas introduction pipe for introducing oxygen gas into the interior of the ion source 7. Reference numeral 14 denotes a PET film which is a non-magnetic substrate, and the film 14 is sent out from a delivery roller 5, passed through a cooling roller 4, and wound onto a take-up roller 6. 15 is a shielding plate provided with an opening 16, which defines the evaporation angle θ. Reference numeral 17 denotes a second gas introduction pipe for introducing oxygen gas into the vicinity of the opening 16.

In this device, the oxygen gas introduced into the ion source 7 through the first gas introduction pipe 13 is released from the filament 10, and thermionic electrons are accelerated by the anode electrode 11 to which a positive voltage is applied. It is ionized by collision with

[0020] Oxygen ions and electrons generated by this ionization become oxygen plasma. Among the above oxygen plasmas,
Oxygen ions 18, which are one of the components of the magnetic thin film, are mainly radiated outward from the opening of the ion source 7.

The release of the oxygen ions 18 occurs because the external pressure is smaller than the repulsive force with the anode electrode 11 having a positive voltage and the pressure inside the ion source 7, and its kinetic energy is small.

However, the oxygen ions 18 have large internal energy. In other words, it has more energy than neutral oxygen by the amount of ionization energy.

The released oxygen ions 18 and the like are simultaneously mixed with the Co vapor 19 generated from the crucible 3 and the oxygen gas 20 supplied from the second gas introduction pipe 17 into the film 14.
is irradiated. At that time, the oxygen ions 18 released
A part of the gas collides with the oxygen gas 20 and the Co vapor 19 to bring them into an energetically excited state. These oxygen and Co reach the film 14 and form a Co--O based magnetic thin film 50 which is a ferromagnetic metal oxide.

When the oxygen (including oxygen ions) and Co in the energy excited state reach the film 14, they release energy. The released energy promotes the miniaturization of the crystals when the Co--O based magnetic thin film 50 is formed, and improves the orientation of the crystals.

[0025] Since the film 14 is formed while moving, there is no charge-up.

A Co--O based magnetic thin film 50 was formed on the film 14 using the above-mentioned manufacturing apparatus under the film-forming conditions shown in FIG.

Next, sample 1 was formed under the above-mentioned film forming conditions.
The magnetic properties, etc. of Sample 2 and Comparative Example prepared without using ion source 7, that is, without irradiating oxygen ions, were measured.

FIG. 3 shows their magnetic property values. Further, main parts of the B-H curves of Sample 1, Sample 2, and Comparative Example are shown in FIGS. 4 to 6, respectively.

As can be seen from FIG. 3, the perpendicular coercive force, in-plane coercive force, perpendicular anisotropy magnetic field, and saturation magnetic flux density of Sample 1 and Sample 2, which were irradiated with oxygen ions, were compared with those not irradiated with oxygen ions. It has almost the same characteristics as the example.

However, according to FIGS. 4 to 6, in Samples 1 and 2 that were irradiated with oxygen ions, the part a of the B-H curve with hysteresis characteristics was steeper than in the comparative example that was not irradiated with oxygen ions. It can be seen that This is because the crystals constituting the magnetic thin film 50 formed by oxygen ion irradiation are made finer and the crystal orientation is improved, and as a result, the magnetization (spins) is aligned in an orderly manner by a weaker magnetic field than in a comparative example in which oxygen ions are not irradiated. It is thought that this is because of this.

Next, the recording and reproducing characteristics of Sample 1, Sample 2, and Comparative Example were measured. First, the frequency characteristics of the reproduced output were measured. The results are shown in FIG. From this result, it can be seen that samples 1 and 2 irradiated with oxygen ions can obtain higher reproduction output in the high frequency region than the comparative example in which no oxygen ions are irradiated.

Next, recording and reproducing characteristics at a frequency of 5 MHz were examined while changing the recording current Irec. The results are shown in Figure 8. From this result, sample 1 and sample 2 irradiated with oxygen ions
It can be seen that optimal recording and reproduction can be performed with a lower recording current than the comparative example prepared without oxygen ion irradiation. This indicates that the spins can be oriented by a weak magnetic field, and is considered to mean that the crystal orientation has been improved.

Next, an isolated reproduction waveform was observed when a signal was recorded at a frequency of 0.5 MHz. Isolated reproduction waveforms of Sample 1, Sample 2, and Comparative Example are shown in FIGS. 9 to 11, respectively.

These isolated reproduction waveforms have an asymmetric dipulse-like waveform, and from this, the recording medium has magnetization in the perpendicular direction (
It can be seen that the perpendicular magnetization component) remains.

The concept of the isolated reproduction waveform will now be explained with reference to FIGS. 12 to 14. FIG. 12 shows a case where only the perpendicular magnetization component remains in the recording medium, and shows a symmetric dipulse shape. FIG. 13 shows a case where only parallel magnetization components remain in the magnetic medium, and shows a single pulse shape.

Furthermore, when both the perpendicular magnetization component and the parallel magnetization component remain in the magnetic medium, the isolated reproduction waveform of the di-pulse shape for the perpendicular magnetization component and the single-pulse shape for the parallel magnetization component interfere, resulting in the result shown in FIG. An isolated reproduced waveform with an asymmetric dipulse shape as shown is obtained.

From this, it can be seen that the larger the output ratio of the isolated reproduced waveform of the asymmetric dipulse shape (diepulse ratio = B/A, where A is the larger one), the more the perpendicular magnetization component is in the magnetic medium. , indicating that it is an excellent recording medium for perpendicular magnetic recording.

Below, the dipulse ratios of Sample 1, Sample 2, and Comparative Example were determined from FIGS. 9 to 11. Below, Figure 15
Shown below.

From FIG. 15, it can be seen that sample 1 and sample 2 irradiated with oxygen ions have a high die pulse ratio of 0.6. However, in the comparative example in which the oxygen ion beam is not irradiated, the dip pulse ratio is only as low as 0.3. Therefore, it can be seen that by irradiating the recording medium with oxygen ions, the perpendicular magnetization component increases.

This is considered to be because the crystals constituting the recording thin film formed by oxygen ion irradiation became finer and the crystal orientation was improved.

In the above measurements, the magnetic recording medium was wound around a drum having a diameter of 62 mm. The linear velocity of the magnetic recording medium is 3.8 m/s. The magnetic head used was a MIG head with a gap of 0.22 μm and a number of winding turns of 20.

According to the method for manufacturing a magnetic recording medium as described above, oxygen ions having low kinetic energy hardly damage the magnetic recording medium. Furthermore, the internal energy of oxygen ions gives energy to oxygen gas, Co, and the like.

In particular, in order for the irradiated oxygen ions to efficiently bring the introduced oxygen molecules into an energetic state such as oxygen ions, energy is added to the formed crystals, so the crystals are It is thought that the crystal orientation is improved by miniaturization. It is also believed that the characteristics of the magnetic thin film related to the effective spacing amount can be improved. Therefore, the magnetic properties in the high frequency region are improved, and the optimum recording current during recording and reproduction can be reduced.

[0044] Furthermore, since the oxygen ions are one of the constituent components of the magnetic thin film, for example, problems such as residual Ar in the magnetic thin film affecting the magnetic properties that occur when using Ar ions etc. will not occur.

Furthermore, in the above manufacturing method, since no heat treatment is required, a nonmagnetic substrate with low heat resistance can be used.

[0046]

Effects of the Invention According to the manufacturing method of the present invention, when producing a magnetic thin film made of a ferromagnetic metal oxide as a magnetic recording medium, the magnetic thin film is irradiated with ions of constituents of the magnetic thin film. To form this, the crystals of the magnetic thin film are made finer,
It is possible to provide a recording medium with improved crystal orientation and improved recording and reproducing efficiency, particularly in a high frequency region.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a magnetic tape manufacturing apparatus according to the present invention.

FIG. 2 is a diagram showing conditions for forming magnetic thin films of the present invention and a comparative example.

FIG. 3 is a diagram showing characteristic values such as magnetic properties of the magnetic tape produced by the method of the present invention together with comparative examples.

FIG. 4 is a diagram showing a part of a B-H curve of a magnetic tape produced by the method of the present invention.

FIG. 5 is a diagram showing a part of a B-H curve of a magnetic tape produced by the method of the present invention.

FIG. 6 is a diagram showing part of a B-H curve of a magnetic tape as a comparative example.

FIG. 7 is a diagram showing the frequency characteristics of the reproduction output of a magnetic tape produced by the method of the present invention together with a comparative example.

FIG. 8 is a diagram showing the recording current characteristics of the recording and reproducing characteristics of a magnetic tape prepared by the method of the present invention together with a comparative example.

FIG. 9 is an oscilloscope waveform diagram of an isolated reproduction waveform of a magnetic tape created by the method of the present invention.

FIG. 10 is an oscilloscope waveform diagram of an isolated reproduction waveform of a magnetic tape created by the method of the present invention.

FIG. 11 is an oscilloscope waveform diagram of an isolated reproduction waveform of a comparative example.

FIG. 12 is a schematic diagram of an isolated reproduction waveform for explaining the present invention.

FIG. 13 is a schematic diagram of an isolated reproduction waveform for explaining the present invention.

FIG. 14 is a schematic diagram of an isolated reproduction waveform for explaining the present invention.

FIG. 15 is a diagram showing the dipulse ratio of the isolated reproduction waveform according to the present invention together with a comparative example.

[Explanation of symbols]

9 Ferromagnetic metal 14 Non-magnetic substrate 18 Oxygen ion 20 Oxygen gas 50 Magnetic thin film

Claims (2)

[Claims] 1. A method for manufacturing a magnetic recording medium, comprising depositing a ferromagnetic metal on a non-magnetic substrate in an oxygen atmosphere to form a magnetic thin film made of a ferromagnetic metal oxide, the method comprising: forming the magnetic thin film; A method for manufacturing a magnetic recording medium, comprising irradiating with ions of a constituent of the magnetic thin film. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the ions of the constituent are oxygen ions.