JPH0816975B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium having a ferromagnetic metal or alloy thin film as a magnetic recording medium layer, and in particular, it has low noise and S / N (output). The present invention relates to a highly reliable ferromagnetic thin film magnetic recording medium having an excellent noise-to-noise ratio characteristic.

[Conventional technology]

In the conventional ferromagnetic thin film magnetic recording medium, the main cause of noise during magnetic recording / reproduction is that a region where the magnetization direction is disturbed (magnetization transition region) is formed at the boundary of the recording bit. It is discussed on page 16 of the summary of lectures by the Japan Institute of Applied Magnetics (October 1981).

[Problems to be solved by the invention]

A ferromagnetic thin film type magnetic recording medium using a ferromagnetic metal thin film or a metal oxide thin film as a magnetic recording layer (magnetic layer) has a high coercive force and a high saturation magnetic flux density, and the magnetic layer can be easily thinned. It has the feature of being These properties are indispensable characteristics for achieving high density recording of the magnetic recording medium, and the next-generation magnetic recording medium for high density recording, which replaces the coating type magnetic recording medium which is widely used at present. Is highly expected as. However, although the ferromagnetic thin film type magnetic recording medium can be relatively easily achieved in terms of improvement of the reproduction output, the noise of the magnetic recording medium is large and a medium excellent in S / N characteristics cannot always be obtained. was there.

Several studies have been conducted on the cause of noise in this ferromagnetic thin film magnetic recording medium. For example, in the above-mentioned document [5th Annual Meeting of the Applied Magnetics Society of Japan (1981) p16], As a main cause of generation of noise during signal recording, the magnetization transition region occurring at the recording bit boundary is mentioned, and it is shown that the noise increases almost in proportion to the recording density. Therefore, how to reduce this proportional constant is an important factor in obtaining a high S / N magnetic recording medium. However, it is still unknown how the noise of the magnetic recording medium is related to the magnetic characteristics of the magnetic thin film of the medium, and it has been a way to obtain a high S / N magnetic recording medium.

An object of the present invention is to specify magnetic characteristics that a magnetic thin film should have in order to reduce noise of a ferromagnetic thin film type magnetic recording medium, and to provide a magnetic recording medium having high S / N characteristics. It is in.

[Means for solving problems]

The object of the present invention is to obtain a rotation history loss integrated value obtained by measuring a magnetic thin film to be a magnetic recording layer with a magnetic torque meter.
This is achieved by using a magnetic recording medium having a magnetic thin film having a R _H (Rotational Hysteresis Integral) in the range of 0.4 to 1.3.

The magnetic recording medium of the present invention will be specifically described below. Now, when measuring the magnetic anisotropy of a magnetic thin film sample using a magnetic torque meter, normally, when a strong magnetic field is applied to the magnetic thin film sample and rotated, a 180-degree symmetry as shown in FIG. A torque curve is obtained. Then, the magnetic field is
When it is rotated 0 degree and then rotated in the opposite direction again, the magnitude of the torque passes over the curve drawn previously and no hysteresis occurs. However, when the magnetic field is weakened, as shown in FIG. 3 (b), when the magnetic field is rotated in one direction and then rotated again in the opposite direction, the magnitude of the torque can no longer pass on the same locus. Instead, hysteresis appears. Third
Area enclosed by two curves shown in Figure (b) In the formula, L represents the magnitude of the torque per unit volume of the sample, and θ represents the rotation angle. ) Is called a rotation history loss and depends on the magnitude of the magnetic field. Further, the rotation history loss integrated value R _H is obtained by comparing the above-mentioned rotation history loss Wr with the saturation magnetic flux density Is.
Value divided by and integrated by the reciprocal of the magnitude H of the magnetic field That is, it is a standard for indicating the mechanism of reversal of the magnetization of the magnetic thin film. Normally, if the magnetization reversal follows the simultaneous rotation model, R _H will be 0.4, and R _H will increase as the magnetization reversal due to domain wall motion is included, and if magnetization reversal occurs only by 180 degrees domain wall motion. Becomes 4.0.

The magnetic thin film, which is the magnetic recording layer of the magnetic recording medium of the present invention, is made of Co, Ni or Fe, a simple metal, or an alloy containing these elements as a main component, and further has a low rotational history loss integral value R _H. In addition, non-magnetic elements such as Cu, V, Z
0.1 to 15 at (atoms) of at least one element such as r and Ru
% Is preferable, and a more preferable range is 3 to
It is 8 at%. When the content of the above elements is less than 0.1, the noise reducing effect is small, and when it exceeds 15 at%, the coercive force and the saturation magnetization are decreased, and the performance as a magnetic recording medium is deteriorated, which is not preferable.

[Action]

In the magnetic recording medium of the present invention, the rotation history loss integrated value
Setting R _H in the range of 0.4 to 1.3 means that the magnetization reversal mechanism of the magnetic thin film used as the magnetic recording medium should be as close as possible to the simultaneous rotation model,
It is considered that it is preferable to control the magnetization reversal due to the domain wall movement as much as possible in order to reduce the noise of the magnetic recording medium. And the rotation history loss integral value
When R _H is less than 0.4, the magnetic thin film is in a range in which it cannot theoretically exist as a magnetic substance, and when R _H exceeds 1.3, the size of the magnetic domain becomes large, and therefore the noise of the magnetic recording medium increases, which is preferable. Absent.

Furthermore, in the magnetic thin film of the present invention, Cu, V, Zr, Ru
Addition of a suitable amount of a non-magnetic element, such as, has the effect of lowering the rotation history loss integral value R _H , and thus an effect of obtaining a high S / N medium is produced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in more detail with reference to the drawings.

Example 1 A surface of a substrate made of Cu—Sn plated Al—Mg alloy having a diameter of 130 mm is mirror-polished, alkali degreased and washed with water, and then the thickness is reduced to 0.
After forming various chemical Ni-P plating films in various ranges of 1000Å, 750Å thickness of Co-20at% Ni-0.8at% is formed on the surface.
A magnetic thin film of P was formed by electroplating. Further, this plated disk was heated in air to a temperature of 300 ° C. and surface-oxidized for 50 minutes to form a deep blue oxidation protection film.

The reproduced disc and the noise of the plated disc manufactured as described above were measured in the following directions. A ring head having a track width of 31 μm and a gap length of 0.8 μm was used as the magnetic head, and the recording / reproducing characteristics were evaluated under the conditions of a flying height of 0.2 μm and a peripheral speed of 20 m / sec. A 6 mm square sample was cut out from the disk for which the recording / reproduction characteristics had been evaluated, a hysteresis curve was obtained using a sample vibrating magnetometer, and the saturation magnetic flux density Is, coercive force Hc, and squareness ratio Ir / Is were measured. Further, using a magnetic torque meter, the rotation history loss integral value R _H was obtained by the method described above.
Fig. 1 shows the magnetic recording medium noise / saturation magnetic flux density (μVrms
/ G) and S / N (dB) and the integrated value of rotational history loss R _H. However, since the saturation magnetic flux density Is may differ between the magnetic thin film samples used for the measurement, the magnetic recording medium noise N is divided by the saturation magnetic flux density Is. As can be seen, there is a uniform relation between the rotation history loss integrated value R _H and the medium noise N, as the rotation history loss integrated value R _H is small, medium noise is reduced, in particular R _H When it was smaller than 1.3, the S / N ratio was 35 dB or more, which was a very excellent magnetic property.

(Example 2) The surface of a substrate made of a Ni-P plated Al-Mg alloy having a diameter of 130 mm was mirror-polished, washed with water, and then heated to a temperature of 150 ° C.
Ar gas pressure is 5,10,15mTor by magnetron sputtering method
r, input power is 1.6, 6.4, 16W / cm ² and thickness 2500
After forming the Cr film of Å, Co-30at% Ni or Co-30at% Ni-5.5at% Cu under various Ar gas pressures and input power conditions,
Alternatively, a magnetic thin film made of an alloy of Co-30at% Ni-11at% V was formed to a film thickness of 600Å. Furthermore, a carbon protective film was continuously formed to a film thickness of 400 Å to manufacture a magnetic disk.
Recording / reproducing characteristics, magnetic characteristics, and rotation history loss integral value R _H of these disks were measured in the same manner as in Example 1. The results are shown in FIG. As is clear from the figure, when Cu or V element is added to the magnetic thin film, noise of the magnetic recording medium is reduced and S / N is improved.
Also in this case, the result is that the medium noise decreases as the rotation history loss integral value R _H decreases. The result of Example 1 is shown by the broken line 4 in FIG. 2, but the curves are almost the same. Even in the case of Example 2, when the rotation history loss integrated value R _H is 1.3 or less, the S / N is 35 dB. It has shown that it becomes above.

(Example 3) In order to improve the corrosion resistance of the magnetic thin film, the composition of the magnetic thin film was changed to Co-30at% Ni-5at% Zr or Co-30at% Ni-4at%.
A magnetic disk was manufactured under the same conditions as in Example 2 except that Zr-1at% Ru was used. Recording / reproducing characteristics, magnetic characteristics, and rotation history loss integral value R _H of these disks were obtained by the same method as in Example 1. As a result, the magnetic thin film was changed to Co-30at% N
In the magnetic disk with the composition of i-5at% Zr, the rotation history loss integrated value R _H was 1.1, the magnetic disk noise / saturation magnetic flux density was 1.0 × 10 ^-3 μVrms / G, and the S / N was 38 dB. . Further, in the magnetic disk having the composition of Co-30at% Ni-4at% Zr-1at% Ru as the magnetic thin film, the rotation history loss integrated value R _H ,
Magnetic disk noise / saturation magnetic flux density value and S / N
Were 0.9, 0.5 × 10 ^-3 μVrms / G and 42 dB, respectively.
These values are approximately located on the curves shown in FIGS. 1 and 2.

As is clear from the embodiments of the present invention described above, noise and rotation history loss integral values are different even when the composition of the magnetic thin film is different and the manufacturing method of the magnetic thin film is completely different such as the plating method and the sputtering method. It can be seen that they have the same relationship between R _H. This means that in order to achieve low noise and high S / N of the ferromagnetic thin film magnetic recording medium, it is essential to reduce the rotation history loss integral value R _H of the magnetic thin film. It shows that it has become.

〔The invention's effect〕

As described in detail above, the ferromagnetic thin film magnetic recording medium of the present invention in which the range of the rotation history loss integral value R _H is 0.4 to 1.3 can significantly reduce the medium noise, and S /
A highly reliable magnetic recording medium having excellent N characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the medium noise and S / N of the magnetic disk manufactured in Example 1 of the present invention and the integrated value of the rotation history loss, and FIG. 2 is the magnetic disk manufactured in Example 2 of the present invention. 3 is a graph showing the relationship between the medium noise and S / N of Fig. 3 and the rotation history loss integral value. Fig. 3 (a) is a torque curve diagram when the magnetic torque of the magnetic thin film sample is measured under a strong magnetic field condition. b) shows a torque curve diagram when the magnetic torque of the magnetic thin film sample was measured under a normal magnetic field condition. 1 …… Torque curve measured in strong magnetic field 2 …… Torque curve measured in normal magnetic field (right rotation) 3 …… Torque curve measured in normal magnetic field (left rotation) 4 …… Medium noise vs. R _H curve 5 …… S / N vs. R _H curve 6 …… Medium noise vs. R _H curve 7 …… S / N vs. R _H curve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norikazu Sekida 2880, Kozu, Odawara-shi, Kanagawa Hitachi Ltd. Odawara factory (72) Inventor Takeo Yamashita 1-280, Higashikoigakubo, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Hiroyuki Suzuki 1-280, Higashi Koigakubo, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Yoji Kitazaki 2880, Kozu, Odawara, Kanagawa Stock Company Hitachi Ltd. Odawara Plant ( 72) Inventor Masaki Oura 2880, Kozu, Odawara, Kanagawa Stock company, Hitachi Ltd. Odawara factory (56) References JP 59-84407 (JP, A) JP 60-35326 (JP, A)

Claims (2)

[Claims] 1. A magnetic recording medium in which a magnetic thin film made of a ferromagnetic metal or alloy is provided as a magnetic recording layer on a non-magnetic substrate, while applying a magnetic field to a magnetic thin film sample taken from the magnetic recording medium. After rotating 360 degrees, rotate it in the opposite direction, adjust the magnitude of the magnetic field so that hysteresis appears without the forward rotation torque curve and reverse rotation torque curve passing on the same trajectory, An area surrounded by two curves of rotation and reverse rotation is represented by a rotation history loss Wr represented by the following formula (1), (In the formula, L represents the torque magnitude of the unit volume of the sample, and θ represents the rotation angle.) The rotation history loss value represented by the above formula (1)
Wr is divided by the saturation magnetic flux density Is of the magnetic thin film, and is further integrated by the reciprocal of the magnitude H of the magnetic field, and is represented by the rotational history loss integral value R _H shown by the following formula (2), The rotation history loss integral value R _H shown by the above equation (2) is 0.4 to
A magnetic recording medium comprising a magnetic thin film within the range of 1.3 as a magnetic recording layer. 2. The magnetic thin film is a simple metal of Co, Ni or Fe,
Alternatively, it is made of an alloy containing at least one element selected from Co, Ni, and Fe as a main component, and further contains at least one element selected from Cu, V, Zr, and Ru in the above metal or alloy. The magnetic recording medium according to claim 1, wherein the magnetic recording medium contains 0.1 to 15% by atomic%.