JPS61261815A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a vertical magnetic recording medium having a protective film which is excellent in durability and weatherability by providing a thin film consisting of plural nitrides as the protective film on a vertical magnetized film. CONSTITUTION:The magnetic recording medium 5 is formed by providing a high permeability soft magnetic film 2 consisting of Fe-Ni 'Permeability(R)', etc. to 0.5mum thickness on a high-polymer flexible base 1 consisting of, for example, a polyimide film having about 50mum thickness, forming the vertical magnetized film 3 consisting of a Co-Cr layer to about 0.2mum thickness thereon and providing further the protective film 4 which is the thin film thereon. The film 4 is formed of a thin film of AlN-TiN or Si3N4-TiN. Either thin film is formed by a sputtering method under prescribed conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perpendicular magnetic recording medium, and more particularly to an improvement in a protective film provided on the surface of a perpendicularly magnetized film.

[Conventional technology]

Over the past few years, research has been actively conducted on perpendicular magnetic recording and reproducing systems as a next-generation high-density magnetic recording and reproducing system. The magnetic recording medium used in this perpendicular magnetic recording/reproduction method is a perpendicular magnetic recording medium in which the direction of magnetization is perpendicular to the magnetic layer. This perpendicular magnetic recording medium is made of polyimide or polyethylene terephthalate (PET), etc. (7), as shown in FIG. 4, which shows an enlarged cross section of the main part.
High magnetic permeability soft magnetic film 12 made of Fe-Ni permalloy or the like as a first layer on the polymer 7 xypul base 11
It is constructed as a two-layer film medium in which a perpendicular magnetization film 13 made of Co--Cr or the like is formed as a second layer thereon.

In order to perform perpendicular magnetic recording and reproduction using the above-mentioned recording medium made of this two-layer film medium, as shown in FIG. An auxiliary magnetic pole excitation type magnetic head is constructed by arranging an auxiliary magnetic pole 24, which has a high magnetic permeability magnetic block 23 and a winding 22 wound around it for transmitting and receiving electric signals, facing each other with the recording medium sandwiched therebetween. used. Further, in the perpendicular magnetic recording and reproducing method, magnetic recording and reproducing are performed by disposing the perpendicular magnetization film 13 so as to be moved in the direction of arrow A while being pressed against the main magnetic pole 21.

First, in order to perform magnetic recording, a magnetic field is generated in the auxiliary magnetic pole 24 by passing an information signal current from an appropriate signal processing circuit (not shown) through the winding 22, and the main magnetic pole 21 is affected by the action of this magnetic field. A sharp perpendicular magnetic field is generated, and this sharp perpendicular magnetic field causes magnetization reversal in the perpendicularly magnetized film 13, thereby performing magnetic recording in the perpendicular direction.

In order to reproduce the signals magnetically recorded in this way, the main magnetic pole 21 is magnetized by the perpendicular magnetic field generated by the magnetization of the perpendicularly magnetized film 13, and the auxiliary magnetic pole 24 is magnetized by the change in magnetization of the main magnetic pole 21. The current induced in the winding 22 in response to the change is taken out to the outside and further taken out as a necessary electrical signal by an appropriate signal processing circuit.

By the way, in order to increase the recording density in the perpendicular magnetic recording and reproducing system configured as described above, it is necessary to minimize the electromagnetic conversion loss between the magnetic flux and the recording medium. Therefore, for that purpose, the main magnetic pole 21
The medium and the medium are operated in close contact with each other. In other words, the main magnetic pole 21 is pressed against the medium by utilizing the flexibility of the medium, and conversely, the medium is pressed against the main magnetic pole 21 by its own elastic force. It is now possible to

In this way, a large load is applied between the main magnetic pole 21 and the medium, and since the medium rotates at a high speed of, for example, 1800 rpm, these A large frictional force will be generated between them. Therefore, the main magnetic pole 21 is worn out, and among the films forming the medium hill, the perpendicularly magnetized film 13 in particular is damaged, which is a practical problem. In order to solve this problem, it is desirable to provide a protective film with lubricating properties on the surface of the perpendicularly magnetized film 13.
and carbon dioxide/recon (S102) are being considered.

Furthermore, in Japanese Patent Application Laid-open No. 57-176537, on the film surface of a Co-Cr alloy as a perpendicular magnetization film,
Nb + Ta + Cr, Mo, W, A
l□03. Sin□, TiO2゜ZrC)2 +
It has also been proposed to provide a coating with one selected from the group Ta205 + Cr2O3 and Ba-ferrite.

[Problem that the invention seeks to solve]

However, in order to reduce the above-mentioned electromagnetic conversion loss, it is better that the protective film interposed between the main pole of the perpendicular magnetic head and the perpendicular magnetization film of the magnetic recording medium be as thin as possible, and preferably 500 mm (- 0.05 μm) or less. However, the conventional protective film made of the above-mentioned materials has a drawback in that the thinner the protective film, the shorter the lifespan. Therefore, an object of the present invention is to provide a perpendicular magnetic recording medium having excellent durability and having a thin protective film of 500 mm or less.

[Means and actions for solving the problem] In this magnetic recording medium, is++Al or Ti is deposited on the perpendicularly magnetized film.
A thin film made of a plurality of nitrides such as the following is formed as a protective film.

〔Example〕

FIG. 1 is an enlarged sectional view of essential parts on a perpendicular magnetic recording medium showing an embodiment of the present invention. For example, this magnetic recording and reproducing process is carried out on a polymeric flexible base 1 made of a polyimide film with a thickness of about 50 μm, and an F with a thickness of about 0.5 μm.
A high permeability soft magnetic film 2 made of e-Ni permalloy or the like is provided, on which a perpendicularly magnetized film 3 made of a Co-Cr layer or the like with a thickness of about 0.02 μm is formed, and a protective film made of a thin film according to the present invention is further formed thereon. A membrane 4 is provided.

In this concrete pile, the protective film 4 is an AlN-TiN thin film or an S! It is formed of a thin film of sN4TiN.

(2) AlN-TiN thin film To form this thin film, small Ti pellets (51BX5yliX1 word thick) are evenly arranged on an Al target at an area ratio of 1:1. Then, 2. Ox ] A clean vacuum is created by evacuation using a cryopump or the like to below O-'Torr. After cooling, Ar and N2 gases are introduced at a ratio of 1=1 at a low pressure (on the order of 10-3 Torr), and reactive sputtering is performed with an input power of 100W. Then,
A protective film 4 of AlN-TiN with a film thickness of 4 ooi or less is obtained ■ SI3N4 TIN thin film To form this thin film, a small TIN film is formed on a wafer of Sl.
i-pellet (5 width x 1 side thickness) in area ratio 1:1
Arrange them evenly. Then, sputtering is performed using a sputtering apparatus under exactly the same conditions as in the case (2) above. As a result, a 5i3N4-TiN protective film having a thickness of 400A or less is obtained.

Further, the AlN-TiN thin film and the 513N4 TIN thin film obtained as described above are amorphous or mixed crystal.

Next, the perpendicular magnetic recording medium obtained in this way was
The medium was cut into inch diameter pieces, rotated at 10 m/sec, and subjected to a durability test using an auxiliary magnetic pole excitation type perpendicular magnetic nodule, and the following results were obtained. In addition,
This data is an experimental result for what was found to be amorphous. The test was conducted by first recording a 5 KBPI signal on the perpendicular magnetic recording medium, and then tracking the time change of the maximum value of the reproduction output and the time change of the reproduction envelope in the same trunk.

FIG. 2 is a characteristic diagram showing changes in the maximum value of reproduction output with respect to elapsed time. Perfluoroalkyl polyether (fluorine-based oil) was previously considered as a protective film.
In the same test as above, the perpendicular magnetic recording medium i coated on the surface of the perpendicular magnetization film 3 crashed in one hour, but the perpendicular magnetic recording medium i of this example
It was found that although the level decreased to a certain degree, it remained almost unchanged after that, and that sufficient reproduction output could be obtained even after at least 30 hours had elapsed. These 30 hours are equivalent to approximately 6.5 million buses.

FIGS. 3(a), (b), and (c) are diagrams showing reproduction envelope waveforms, (a) after 0 hours, (b) after 1 hour, (
c) shows the output waveform after 30 hours. Figure 3 (a
) to (C), by using the perpendicular magnetic recording medium of this example, the reproduction envelope hardly changes regardless of the passage of time.

In FIGS. 3(a) to 3(C), the units of the ■ scale are 200 mV on the vertical axis and 2 mS on the horizontal axis.

Also, as in this example, the thickness is 400A or less.
It has been experimentally confirmed that even if the protective film 4 of A is provided, the life is not shortened. Thus, according to this embodiment, the protective film 4 with a thickness of 400 A can be provided on the surface of the perpendicularly magnetized film 3. Therefore, a perpendicular magnetic recording medium with low electromagnetic conversion loss and excellent lubricity and durability can be obtained.

In the above embodiment, the durability test was performed using an auxiliary pole excitation type magnetic head, but it is possible to obtain the same effect even if the durability test is performed using a main pole excitation type magnetic head. Of course.

In the present invention, it goes without saying that composition ratios other than those of the protective film created in the above embodiments may be used.

〔Effect of the invention〕

As mentioned above, in the present invention, a thin film made of a plurality of nitrides is formed on a perpendicularly magnetized film as a protective film.
It is possible to provide a perpendicular magnetic recording medium having a protective film that is harder, more durable, and has better weather resistance than conventional films in which each film is formed individually.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of essential parts of a perpendicular magnetic recording medium according to an embodiment of the present invention, and FIGS. 2 and 3 (a) to (c) illustrate durability of the perpendicular magnetic recording medium according to the present invention. Characteristic diagrams showing the test results, Figure 4 is an enlarged sectional view of main parts showing the configuration of a conventional perpendicular magnetic recording medium, and Figure 5 shows recording by a magnetic head on the perpendicular magnetic recording medium shown in Figure 4 above. FIG. 3 is an enlarged sectional view of a main part showing a state of reproduction. 3.13...Perpendicular magnetization film 4...Protective film 5, 1O--=--== Perpendicular magnetic recording medium patent applicant Olympus Optical Industry Co., Ltd.8゜/hole:, """"""g'1A-1

Claims (1)

[Claims] A perpendicular magnetic recording medium having at least one layer of perpendicular magnetization film having an axis of easy magnetization perpendicular to the film surface, wherein a thin film made of a plurality of nitrides is protected on the perpendicular magnetization film. A perpendicular magnetic recording medium characterized in that it is provided as a film.