JP3052211B2 - Perpendicular magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, as external storage devices used in personal computers, laptop computers and the like have been required to be smaller and larger in capacity, the density of floppy disk type magnetic recording devices has been increased. . This method of increasing the density is roughly divided into a method of increasing the recording frequency and a method of increasing the recording frequency.
There are two methods: increasing the linear recording density to increase the track recording amount, and increasing the track density to increase the number of tracks per disk by reducing the track pitch and track width. Among them, use of a perpendicular magnetic recording medium has been studied to increase the linear recording density, and a barium ferrite coated disk has been partially put to practical use. This is compared to the conventional longitudinal recording media.
Since there is no demagnetizing field in principle, the higher the recording density, the more stable the magnetization, and it is possible to easily achieve several times higher density recording than before. Here, in order to further improve the linear recording density, a CoCr film or a CoC film containing no non-magnetic material such as a binder is used.
A perpendicular magnetic recording medium using a metal thin film in which r, Ti, Ta, Pt, B, or the like is added as a third element is being studied. On the other hand, the increase in track density is 200 [TPI], which is about twice that of the conventional about 100 [TPI].
Is exceeded, servo control of the head is required on the driver side of the floppy disk, and development for this is being advanced.
Those having a length of 500 to 500 [TPI] are being put to practical use also in the longitudinal recording method, and a floppy disk type magnetic recording device having a recording capacity of about 5 times that of the conventional one has appeared. Accordingly, if the linear recording density and the track density can be increased by a perpendicular magnetic recording medium made of a metal thin film, a floppy disk type magnetic recording device having a storage capacity several tens of times at a stroke can be obtained. On the other hand, with regard to a tape-type medium represented by a VTR, if a dramatic increase in the density becomes possible, a high-definition VTR that is currently practically used only for business use will be technically feasible for consumer use. Here, it is known that the relationship between the track width and the reproduction output is substantially proportional, and when the track width is reduced to increase the track density, the reproduction output decreases. Therefore, in order to improve the track density of the floppy disk, it is necessary to increase the output to compensate for the decrease in the reproduction output due to the reduction in the track width. On the other hand, in the case of a tape-shaped medium represented by a VTR, if the advantage of high-density recording of a perpendicular magnetic recording medium is to be used, recording / reproducing at a frequency over a wide band is performed. Therefore, high output is required.

[0003]

However, this C
The reproduction output of a perpendicular magnetic recording medium using an oCr alloy thin film is:
Since the increase is only about 2 dB compared to the conventional application medium using metal magnetic powder, it is necessary to newly develop a reproduction amplifier and a signal processing circuit with low noise, which has been a major obstacle to practical application.

[0004]

According to the present invention, there is provided a magnetic recording medium having a magnetic thin film on a polymer film.
First, a CoCrFe layer is formed as an underlayer on the film, and the composition at this time is Cr: 15 to 20 wt%, F:
e: 3 to 10% by weight, with the balance being Co. The Fe concentration decreases from the lower layer to the upper layer, and the Fe concentration is 0 at the uppermost part of the underlayer.
wt.%, and a thin film having a thickness d of 100 ≦ d ≦ 1500 [A (angstrom)] is formed thereon, and a CoCr alloy thin film or a CoCr alloy is coated with Ti, Ta, Pt, and B as a third element. A perpendicular magnetic recording medium characterized by being added is obtained. That is, the present invention provides a CoC having a component of an easy axis of magnetization in an in-plane direction parallel to the film surface below the CoCr composite layer.
It has been found that the reproduction output can be improved by forming an rFe alloy and providing an underlayer having a concentration gradient from the lower layer to the upper layer with the Fe concentration from the lower layer to the upper layer. It is known that one method for improving the reproduction output of a magnetic recording medium is to reduce the magnetic resistance on a magnetic circuit. For example, in the case of a CoCr alloy thin film, FIG.
As shown in (1), magnetization causing a demagnetizing field appears on the opposite side of the magnetic head, increasing the magnetic resistance and decreasing the reproduction output. Therefore, as shown in FIG. 3, by forming a base layer having an easy axis of magnetization in the in-plane direction between the CoCr layer and the base film, the demagnetizing field can be eliminated and the reproduction output can be increased. On the other hand, there is a problem of matching of the crystal lattice spacing as a condition required as the underlayer in the thin film forming method. That is, the vertical orientation of magnetization of the CoCr film is hcp
Since the material has crystal lattice anisotropy due to the structure, if a material having a lattice spacing significantly different from that of CoCr is selected as the underlayer, the perpendicular orientation of the CoCr film is impaired, the magnetic characteristics are deteriorated, and the electromagnetic conversion characteristics are deteriorated. Gets worse. Therefore, it is desirable to use a thin film in which a third element is added to a CoCr alloy and has an easy axis of magnetization in an in-plane direction as the underlayer. The present inventor has conducted intensive studies on the above points,
By employing Fe as the third element and setting the composition ratio to be large in the lower layer and extremely small or zero in the upper layer, it has been found that the reproduction output of the perpendicular magnetic recording medium using the CoCr alloy thin film can be increased.

[0005]

EXAMPLES The comparative examples and examples will be described in detail above. FIG. 4 shows a sputtering apparatus used in Comparative Examples and Examples of the present invention. Two target electrodes facing the center of the rotating disk-shaped substrate holder are provided, one of which is provided with a CoCr alloy target and the other of which is provided with a CoCrFe alloy target. Comparative Example A 0.3 μm thick CoCr thin film was formed on a 30 μm thick polyimide film by an RF magnetron method. The sputtering pressure at this time was 0.1 [Pa], and R
The F power density is 2.74 [W / cm ² ]. Also,
The CoCr target composition was 17.5 [wt%], and Cr was the balance. [Example 1] In a comparative example, before forming a CoCr layer, CoCr was used.
By Fe alloy target and CoCr target,
An underlayer of a CoCrFe alloy was formed. At this time, the power supplied to each target is changed as shown in FIG. That is, the initially set electric power is applied to the CoCrFe target, and the electric power is reduced as the sputtering time elapses, thereby decreasing the deposition rate. On the other hand, CoCr
The input power is increased in proportion to the elapsed time from the start of sputtering, and the target is CoCrF having a concentration gradient of Fe.
e Create an underlayer. Thereafter, CoCr is used as in the comparative example.
Form a layer. Here, the composition of the CoCrFe target was such that the ratio of Co and Cr in the CoCr target was constant, and the Fe amount was 5 [wt%]. That is, (Co _82.5 Cr _17.5 ) _100-X Fe _X : X = 5 [wt
%] And the thickness was set to 100 [A]. The sputtering pressure of the underlayer is 0.1 [Pa], and the total RF power density applied to the two targets is always 2.74.
[W / cm ² ]. Example 2 In Example 1, the composition of the CoCrFe target was
Cr: 17.0% by weight, Fe: 3% by weight, Co: the remainder were prepared. Example 3 In Example 1, the composition of the CoCrFe target was
Cr: 17.0% by weight, Fe: 10% by weight, Co: remaining were produced. [Example 4] In Example 1, the thickness of the CoCrFe underlayer was set to 500.
[A]. Example 5 In Example 1, the thickness of the CoCrFe underlayer was set to 100
0 [A]. Example 6 In Example 1, the thickness of the CoCrFe underlayer was set to 150
0 [A]. FIG. 6 shows the result of measuring the composition change in the depth direction of the medium in Example 1 by Auger spectroscopy. The interface between the CoCr layer and the CoCrFe layer does not appear clearly, and it can be seen that the Fe concentration gradually increases from the upper part to the lower part of the underlayer. Further, with respect to Comparative Examples and Examples, a carbon protective film having a thickness of 100 [A] was formed, a data disk having a size of 2 inches was formed, and the reproduction output when the recording frequency was 9 MHz was compared. The head used at this time had a gap length of 0.
It was a metal in gap type of 15 [μm] and measured at a disk radius of 20 mm. In Examples 1 to 3, C
The relationship between the Fe concentration of the oCrFe target and the reproduction output
FIG. 7 is a graph. From FIG. 7, the Fe concentration is 3
If it is between 10 and 10 wt%, the reproduction output of about 5 dB
It can be seen that it can be obtained. Further in Examples 1 and 4 to 6
Oite, measured boss was forming a relationship between the thickness of the base layer and the reproduction output
The results are shown in FIG. From FIG. 8, the thickness of the underlayer is 100 to 5
Within the range of 00 [A], almost the same regardless of the film thickness
It can be seen that a reproduction output of

[0006]

As described above, according to the present invention, it is possible to obtain a CoCr perpendicular magnetic recording medium whose reproduction output is greatly increased. Here, in the embodiment of the present invention, a 2-inch data floppy has been described. However, a floppy disk of another size may be used, and the same effect can be obtained with a tape. Is not limited to the embodiment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the present invention.

FIG. 2 is a schematic view showing the function of an underlayer.

FIG. 3 is a schematic view showing the function of an underlayer.

FIG. 4 is a schematic view of a sputtering apparatus used in an embodiment of the present invention.

FIG. 5 is a diagram illustrating a method of forming an underlayer in an example of the present invention.

FIG. 6 is a composition analysis result of an example of the present invention.

FIG. 7 is an embodiment of the present invention.

FIG. 8 is an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective / lubricating layer 2 Perpendicular recording layer 3 Underlayer 4 Base film 5 Magnetic head 6 Magnetic charge 7 Magnetization 8 Demagnetizing field 9 Vacuum container 10 Substrate holder 11 Base film 12 CoCr target 13 CoCrFe target 14, 15 Sputter power supply 16 Matching box

Claims (1)

(57) [Claims] In a magnetic recording medium having a magnetic thin film on a polymer film, a CoCrFe layer is first formed on the film as an underlayer, and the composition at this time is C
r: 15 to 20 wt%, Fe: 3 to 10 wt%, the balance being Co, the Fe concentration decreases from the lower layer to the upper layer, the Fe concentration is 0 wt% at the top of the underlayer, and the film thickness d is 100 ≦ d ≦ 1500 [A (angstrom)] is formed, and a CoCr alloy thin film or a CoCr alloy is added with Ti, Ta, Pt, or B as a third element. Perpendicular magnetic recording medium.