JPS5921088B2 - Magnetic disk manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic disk having uniform recording/reproducing characteristics and a method for manufacturing the same.

In designing a magnetic disk device, it is preferable that the frequency characteristics of the recording and reproducing characteristics of the magnetic disk-head system be the same for any track on the disk surface.

However, when the magnetic disk medium is made uniform5, the head
Because the relative speed of the disk surface increases as tracks near the outer periphery, the recording density on the medium at a given frequency decreases in inverse proportion to the relative speed, even though the spacing between the head and the disk surface increases. First, the frequency characteristics differ with the tenth track position. In order to improve such non-uniformity in recording and reproducing characteristics, the significance of providing a medium with appropriate non-uniformity has attracted attention, and specific methods have also been proposed.

That is, the method is to increase the medium film thickness closer to the outer circumference in the 15 radial direction in the γ-Fe, O2, and fine particle coated film disk. However, if this method is used, the film becomes thick and the leakage magnetic field from the head is not sufficiently applied to the inside of the medium, resulting in the disadvantage that the overwrite characteristic, which is a practically important characteristic, deteriorates.

Now, in order to obtain uniform frequency characteristics over the entire surface of the disk, it is necessary that the solitary wave half-width PW50 in any track be the same. By the way, from the results of 25 experimental and theoretical studies regarding the correlation between magnetic recording and reproducing characteristics and medium characteristics, the half-width of a solitary wave and the magnetostatic characteristics of the medium Br, Hc (
5. It is known that the relationship between film thickness δ and film thickness δ is as follows. PW5o(Xv/Brδ/Hc(1)) 30 As a result, the half-width actually measured is related as shown in the following equation in consideration of the relative speed V between the disks.

PW, O(x: Brδ/Hc/V(2)35 Therefore, if /Brδ/Hc is changed at the same rate as the circumferential speed V, the half-width will remain constant and will remain constant over the entire surface of the disk. It is expected that similar frequency characteristics will be obtained.

In the previous example, it can be understood that this was attempted to be achieved by controlling the film thickness δ. In contrast, the inventors
? We realized that it is possible to create a medium with similar uniform characteristics using the control method 1.Moreover, in that case, the thickness of the medium does not change over the entire surface of the disk, and the coercive force Hc decreases as it approaches the outer periphery. This has the advantage of making it possible to realize uniform recording characteristics without impairing the overwriting characteristics.Next, it is noted that the magnetic disk according to the present invention can be produced by the following reactive vapor deposition method. In order to improve the performance of magnetic disk devices, it is essential to develop magnetic recording media that enable high-density recording, and as a result of vigorous research in various places, the γ
-Plated metal magnetic films and oxide magnetic thin films are seen as promising media with superior properties to Fe2O3 fine particle coating films.

In particular, the latter is considered to be more suitable for high-density recording because its residual magnetization is 1/2 that of the former, and it has excellent mechanical strength and does not require a protective film. Many methods have been tried to produce this oxide magnetic thin film, but one method is to introduce oxygen gas into a high vacuum container and evaporate iron, iron-based alloys, or their oxides. Therefore, the so-called reactive vapor deposition method for forming magnetic oxide thin films of these metals is a very promising method because of its batch productivity, low processing temperature, and ease of controlling the film thickness and magnetic properties. Therefore, the present inventors carefully investigated the influence of deposition conditions on the magnetic properties of the produced film in forming a magnetic oxide thin film mainly composed of Fe3O4 by reactive vapor deposition. As a result, the saturation magnetic flux density Bs (or residual Magnetic flux density Br) and H
We have discovered a remarkable and characteristic change in c, and have discovered a new method for producing a magnetic disk that meets the above objectives.

Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 shows typical experimental results. i.e. 4×10−
Saturation magnetic flux density Bs and coercive force of iron oxide thin films obtained when iron was evaporated at a deposition rate of about 40 in/sec in a 4T0rr oxygen atmosphere and the substrate temperature was maintained at various temperatures ranging from room temperature to around 300°C It shows the dependence of Hc on substrate temperature Ts. B buttocks TslOOC gradually increases from 200°C and then increases monotonically until around 300°C. On the other hand, Hc increases rapidly from a small value below TslOO°C at 100 to 200°C (however, the rectangularity is not good in this range), reaches a maximum value around 240°C, and begins to decrease at Ts above that. 240℃
In the above cases, the rectangularity is good and the values are almost the same.

Another experimental result shows that Bs and Hc at temperatures above 240°C
The same tendency of change was observed up to 350°C. These trends are the same even if the oxygen pressure and deposition rate are different from those described above. However, in that case, the residual magnetic flux density increases or decreases depending on the degree of oxidation of the produced film, and as a result, at a substrate temperature of 240°C, Br2. It was possible to control over OOO Gauss. mosquito\
Based on the fact that oxide magnetic thin films are created by reactive vapor deposition, by providing appropriate non-uniformity to the substrate temperature distribution in the radial direction, non-uniform distribution of Br and Hc in the formed oxide thin film can be achieved. Therefore, it is possible to create a magnetic disk having uniform recording and reproducing characteristics (particularly frequency characteristics) regardless of the track position. The significance of this manufacturing method will be explained below with reference to examples.OEmbodiment FIG. 2 is a side view of an example of an apparatus for carrying out this manufacturing method, and FIG. 3 is a plan view of the inside of the same apparatus.

In Figures 2 and 3, 1 is a vacuum chamber, 2 is a disk substrate for producing a recording medium, and 3 is a substrate heater for controlling the temperature of the substrate, which is designed to obtain the desired temperature distribution in the radial direction of the substrate. . 4 is a fixed deposition mask whose shape is taken into consideration to obtain a uniform film thickness distribution in the radial direction, 5 is a shutter, 6 is a deposition source, and r is a crystal vibration type for monitoring the deposition rate and film thickness. The detection portion 8 of the film thickness meter indicates a rotation axis around which the substrate rotates during deposition.

In this device, the temperature distribution on the substrate surface by the substrate heating heater is approximately 240°C on the inside (about 130φ) of the substrate and about 300°C on the outside (about 190φ), and the temperature rise in between is almost linear. The heat generation of the heater and its distribution were controlled, and then an iron oxide thin film was formed to a thickness of 2000 mm using Fe as the deposition source and oxygen at a deposition rate of 60λ/Sec and a substrate rotation speed of 15 rpm. As a result of measuring the magnetostatic properties of this iron oxide thin film at each radial position, it was found that in the vicinity of 130φ, Br3.2OO Gauss, Hc45O Oersted, 19
Near 0φ, Br5OOOG. Hc3OOOOe, during which both Br and Hc changed linearly. Since the film thicknesses are the same, the term for film thickness δ is omitted in the second equation,
When determining J Hyakki 4 flea at 130φ and 190φ, they are approximately 2.7 (G/0e) V2 and approximately 4.1 (G/0e), respectively.
) 1/2, and the ratio of both was approximately 1:1.5. Next, an iron oxide thin film was formed on the 200φ disk substrate soil under the same vapor deposition conditions and film thickness to produce an iron oxide thin film disk. When the same disk was installed in a magnetic disk device and its recording and reproducing characteristics were measured, the solitary wave half width was 130φ to 190φ.
It was found that the frequency characteristics were almost the same for all tracks, and as a result, the uniformity of the frequency characteristics was also extremely excellent. On the other hand, no adverse effects were observed on overwriting characteristics or other characteristics.
This result shows that for the above 130φ and 190φ, the peripheral speed ratio is 1:
1.45, and the value depends on the magnetic properties found earlier.
This can be fully understood from the fact that the ratio is close to that of .

In this example, the substrate temperature distribution was set at 240 to 300°C.
However, of course, this width will vary depending on the innermost and outermost track positions covered by the same head in actual use and treatments during or after deposition (e.g. CO doping to the deposition source, heat treatment in air). It is obvious that the temperature range depends on changes in the magnetic properties (particularly Hc), and it goes without saying that the temperature range should be selected as appropriate depending on the situation. As is clear from the foregoing, the present invention provides a magnetic disk having uniform recording and reproducing characteristics over a wide range of the disk surface by providing a non-uniform distribution of residual magnetic flux density and coercive force in the radial direction. It is possible to provide a method for producing a magnetic disk using an extremely simple means of intentionally imparting a non-uniform distribution to the substrate temperature during vapor deposition using a reactive vapor deposition method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the relationship between the magnetostatic properties of an iron oxide thin film produced by the reactive vapor deposition method and the substrate temperature. FIG. 2 is a schematic side view showing an example of a vapor deposition apparatus for producing an oxide magnetic thin film recording medium according to the present invention, and FIG.
It is a top view of the inside of a figure. In the figure, 1 is a vacuum chamber, 2 is a disk substrate, 3 is a substrate heater, 4 is a deposition mask, 5 is a shutter, 6 is a deposition source, 7 is a film thickness meter detection head, 8 is a rotation axis, and 9 is a vacuum gauge measurement 10 is an oxygen gas inlet, and 11 is a vacuum pump exhaust port.

Claims (1)

[Claims] 1. By introducing oxygen gas into a high-vacuum container and evaporating iron or an iron-based alloy or its oxide, iron or an iron-based alloy is deposited on a disk substrate. In a method for forming an oxide magnetic thin film, it has been shown that by providing a substrate temperature distribution that increases toward the outer circumference in the radial direction of the disk substrate, the residual magnetic flux density of the medium increases and the coercive force decreases in the same direction. Features: A manufacturing method for magnetic disks. 2. The method of manufacturing a magnetic disk according to claim 1, wherein the distribution width of the substrate temperature is within a range of 200°C to 350°C or more.