JP2003109213A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium having high coercive force and satisfactory in an S/N ratio. SOLUTION: A pre-coating layer 2 and a NiP based alloy layer 3 are successively layered on a non-magnetic substrate (a glass substrate) 1. A concentrically shaped texture 31 is formed on the principal surface of the NiP based alloy layer 3. A CrMo based alloy base layer 4 having 80-300 Å thickness and <140 Ågrain size, an intermediate layer 5, a CoCrPtB based magnetic layer 6, a protective layer 7 and a lubrication layer 8 are successively layered thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium suitable for a magnetic disk device for recording / reproducing information.

[0002]

2. Description of the Related Art As a structure of a magnetic recording medium, a magnetic disk in which a Co type magnetic layer, a protective layer made of carbon or the like, and a lubricating layer are formed in this order on a non-magnetic substrate is used. Co
In order to improve the in-plane orientation of the magnetic system magnetic layer and improve the electromagnetic conversion characteristics, a Cr system underlayer is formed between the nonmagnetic substrate and the Co system magnetic layer, or the nonmagnetic substrate and the Cr system are formed. Attempts have also been made to form circumferential textured structures between system underlayers.

Further, according to Japanese Patent Publication No. 7-72935, Hc in the circumferential direction is as large as 1200 Oe or more, and a high S / N ratio is obtained.
As a magnetic recording medium having a specific ratio, W was set to 0.% on a disk-shaped non-magnetic substrate that was textured along the circumferential direction.
There is disclosed a magnetic recording medium in which a CrW film containing 5 at% to 30 at% is formed as an underlayer, and a Co-based alloy magnetic film is formed on the underlayer. In order to improve the electromagnetic conversion characteristics up to now, many Cr-based alloy underlayers in which an additive element such as Mo, W, V, or Ti is added to Cr have been proposed. It is considered that it was proposed from the knowledge that the S / N ratio is the best in improving the characteristics.

[0004]

However, the rapid increase in recording density of magnetic recording media in recent years has led to a dramatic improvement in electromagnetic conversion characteristics, that is, a dramatic improvement in S / N ratio, with respect to magnetic recording media. Although required, it has become difficult with the conventional technology to obtain an S / N ratio that sufficiently meets this requirement. The present invention has been made to solve the above problems and has a coercive force of 35
It is an object to obtain a magnetic recording medium having a high coercive force of 00 Oe or more and a good S / N ratio.

[0005]

As a means for solving the above-mentioned problems, the first means is a magnetic recording medium having a Cr-based underlayer and a CoPt-based magnetic layer on a non-magnetic substrate. , On the surface of the non-magnetic substrate or on the surface of a layer formed between the substrate and the magnetic layer, or both,
A concentric circular texture that improves the in-plane orientation of the magnetic layer is formed, and the Cr-based underlayer is a CrMo-based alloy containing Cr and Mo, and the thickness of the layer is 80 to 300.
It is a magnetic recording medium characterized by being Å. The second means is a magnetic recording medium having a Cr-based underlayer and a CoPt-based magnetic layer on a non-magnetic substrate, which is formed on the surface of the non-magnetic substrate or between this substrate and the magnetic layer. A concentric texture that improves the in-plane orientation of the magnetic layer is formed on either or both surfaces of the layer.
The base underlayer is a CrMo-based alloy containing Cr and Mo, and the size of the crystal grains of the CrMo-based alloy forming the layer is less than 140Å is a magnetic recording medium. A third means is that the CoPt-based magnetic layer is CoC.
The first or second is characterized by being an rPtB-based magnetic layer
The magnetic recording medium according to the above means. A fourth means is characterized in that the non-magnetic substrate is a glass substrate, and the concentric texture is formed on a surface of a NiP-based alloy layer formed on the glass substrate. ~
A magnetic recording medium according to any one of the third means. A fifth means is M of a CrMo-based alloy that constitutes the underlayer.
The magnetic recording medium according to any one of the first to fourth means, wherein the content of o is 5 to 30 at%. A sixth means is that the NiP-based alloy layer is formed by sputtering, and the non-magnetic substrate and the NiP are provided between the non-magnetic substrate and the NiP-based alloy layer.
The magnetic recording medium according to any one of the first to fifth means, characterized in that a precoat layer for improving film adhesion to the P-based alloy layer is formed. A seventh means is a magnetic recording medium according to the sixth means, wherein the precoat layer is made of a material selected from Cr, Cr alloys and NiAl. An eighth means is a magnetic recording medium according to any one of the first to seventh means, wherein at least the underlayer is formed by sputtering by applying a negative bias voltage of −100V to −400V. Is.

In solving the above problems, the present inventors confirmed the optimum underlayer for improving the S / N ratio. In this experiment, a magnetic recording medium which has not been used to form a concentric texture and which is generally used in the past (underlayer, CoCr intermediate layer, CoPtCrB magnetic layer, carbon protective layer, perfluoropolyether lubricating layer on a glass substrate In the formed magnetic recording medium), Cr is used as an underlayer.
Magnetic recording media in the case of using the Mo alloy and the CrW alloy were made as prototypes and the electromagnetic conversion characteristics were evaluated. As a result, Cr
The CrW-based underlayer has a higher S / than the Mo-based underlayer.
The N ratio was shown.

It has been confirmed that this is the same result as the previous knowledge that the above-mentioned material CrW has the best S / N ratio in improving the electromagnetic conversion characteristics. However, as a result of many experiments, it has been found that a magnetic recording medium having a concentric circular texture formed on a non-magnetic substrate, as disclosed in Japanese Patent Publication No. 7-72935, gives completely different results.

The present inventors have found that in a magnetic recording medium having a concentric texture formed on a non-magnetic substrate, C
The CrMo-based underlayer has a higher S / N ratio than the rW-based underlayer, which is a characteristic that cannot be conceived from the conventional conclusion, and the recent demand for higher recording density has been found. I found out that I could respond enough.

That is, in the magnetic recording medium in which the concentric circular texture for improving the in-plane orientation of the magnetic layer is formed on the main surface of the non-magnetic substrate on which the magnetic layer is formed, the underlayer is made of Cr. A magnetic recording medium having a high S / N ratio can be obtained by using a CrMo alloy containing Mo and Mo.

Here, the concentric texture form (surface roughness, pitch, etc.) is appropriately adjusted according to the obtained electromagnetic conversion characteristics. Specifically, the surface roughness of concentric circular texture (measured by atomic force microscope (AFM))
The maximum height Rmax is preferably adjusted in the range of 1.5 to 15 nm in order to obtain head flying characteristics corresponding to high recording density.

Also, the radial pitch of the concentric circular texture is set to 0.005 to 0.07 μm,
By suppressing the crystal grain growth in the radial direction, and the radial pitch of these concentric circular textures is formed substantially regularly with respect to the crystal grain size of the magnetic layer, the grain size between textures, that is, The particle size of the entire disc is made uniform.

The concentric texture may be spiral or cross-textured as long as the effect of the present invention can be obtained.

CrMo-based alloys include Ta, in addition to CrMo.
The additive elements such as Ti, Hf, V, Nb, and Mn are added in an amount of 0.05 to
10 at% may be included. Also, O (oxygen), N
A gas such as (nitrogen), H (hydrogen), C (carbon), B (boron) may be added.

Examples of the material of the non-magnetic substrate include glass (including glass ceramics, so-called crystallized glass), ceramics, aluminum, carbon and the like. In particular, like the second means, the non-magnetic substrate is composed of a glass substrate, a NiP alloy layer is formed on the glass substrate, and the concentric texture is formed on the surface of the NiP alloy layer. As a result, a magnetic recording medium having a higher coercive force and a higher S / N ratio can be obtained.

That is, by using a glass substrate as the non-magnetic substrate, excellent smoothness can be obtained when precision-polished as compared with other materials. Therefore, the crystal grain size of the underlayer or magnetic layer formed by the sputtering method can be suppressed from varying depending on the surface state of the substrate, which is advantageous for electromagnetic conversion characteristics.

Further, the glass substrate has good thermal durability unlike the aluminum alloy substrate which has been conventionally used.
By applying heat treatment when forming the magnetic layer, Cr of the material of the underlayer is segregated between the particle diameters of the magnetic layer,
This is advantageous in that a magnetic recording medium having a high coercive force can be obtained. Further, by forming the NiP alloy layer on the glass substrate having good surface smoothness and thermal durability, a bias voltage can be applied to the substrate during the formation of the underlayer and the magnetic layer, which will be described later. It is advantageous because a higher S / N ratio can be obtained.

As for the concentric circular texture, even if the NiP alloy layer is formed on the glass substrate surface after the concentric texture is formed, the NiP alloy layer is formed on the glass substrate and then the NiP alloy layer is formed. A concentric texture may be formed on the surface. The NiP-based alloy layer includes Al, V, Cr, Zr, Nb, Mo, Hf, and T in addition to NiP.
A metal such as a or W may be contained.

The content of Mo in the CrMo alloy is
5 to 30 at% considering the matching of the lattice with the magnetic layer
It is preferable that More preferably, 8-15a
t% is desirable.

The thickness of the CrMo alloy base layer is 50 to 3
00Å is preferable in terms of high S / N ratio. When a CrMo-based alloy underlayer having this thickness is formed, a CoPt-based material, particularly preferably C, is used as the material of the magnetic layer from the viewpoint of high coercive force.
An oCrPtB-based alloy is preferable. By using a CoCrPtB-based alloy, other characteristics such as coercive force Hc can be favorably maintained without increasing the film thickness of the underlayer and thus without deteriorating the S / N ratio.

The NiP-based alloy layer is formed by sputtering, and a precoat layer that strengthens the adhesion between the nonmagnetic substrate and the NiP-based alloy layer is formed to stabilize the characteristics of the NiP-based alloy layer. I can do things. Since the NiP-based alloy layer is formed with a thickness of 500 to 2000Å, the film stress becomes extremely high. The film stress is easily influenced by the sputtering conditions (substrate temperature, gas pressure, etc.), and these conditions must be controlled accurately. If the film stress becomes high for some reason, in the worst case, the film will peel off from the substrate. Therefore, a precoat layer is necessary to prevent the NiP alloy from peeling off from the substrate.

As the precoat layer, an underlayer or a seed layer is formed under the underlayer for the purpose of controlling the crystal grain size of the underlayer. The seed layer is formed of the same material as the crystal structure of the underlayer and the seed layer. For example, Cr, Cr alloys (CrMo, CrV, CrTi, CrTa, Cr
W), B2 crystal structure (NiAl, AlCo, NiAlR
materials such as u). In addition, O for these materials
(Oxygen), N (nitrogen), B (boron), C (carbon), etc. may be added to make the crystal grain size finer.

A higher S / N ratio can be obtained by applying a negative bias voltage of -100 V to -400 V to at least the underlayer to form a film by sputtering.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention will be specifically described below. (Embodiment 1) FIG. 1 is a diagram showing a film structure of a magnetic recording medium according to Embodiment 1. As shown in FIG. 1, Example 1
The magnetic recording medium according to the present invention is a non-magnetic substrate (glass substrate) 1
On top, a precoat layer 2, a NiP-based alloy layer 3, a base layer 4,
The intermediate layer 5, the magnetic layer 6, the protective layer 7, and the lubricating layer 8 are sequentially laminated.

The glass substrate 1 is a chemically strengthened aluminosilicate glass, which has been finely polished (center line average roughness Ra = 0.2 nm (measured by AFM)) by a double-sided polishing machine.

The precoat layer 2 is a CrMo thin film (film thickness 1
The film thickness is 00 angstrom) and is provided to improve the film adhesion between the NiP-based alloy layer 3 and the glass substrate 1.
The CrMo thin film has Cr: 91 at% and Mo: 9 at%.

The NiP alloy layer 3 is made of NiP (Ni: 80).
at%, P: 20 at%) thin film (thickness 800 angstrom). A texture 31 having a maximum height Rmax of 3.5 nm and a radial pitch of 0.025 μm (measured by an atomic force microscope) is concentrically formed on the surface of the NiP alloy layer 3.

The underlayer 4 is a CrMo thin film (thickness: 150 Å) and is provided to improve the crystal structure of the magnetic layer. This CrMo alloy has a Cr: 91
The composition ratio is at%, Mo: 9 at%. The underlayer 4 is formed by sputtering with a negative bias of −300 V applied to promote the crystallinity of the CrMo underlayer.

The intermediate layer 5 is provided for the purpose of improving the crystallinity of the magnetic layer, and is a CoCr thin film (thickness: 30 Å) having a non-magnetic hcp structure.
Co and Cr contents are Co: 65 at% and C, respectively.
r: 35 at%.

The magnetic layer 6 is a CoCrPtB alloy thin film (film thickness: 150 angstrom) and is made of Co, Cr, Pt,
The contents of B are Co: 61 at% and Cr: 20 respectively.
At%, Pt: 12 at%, and B: 7 at%. The composition of the CoCrPtB alloy thin film is such that Cr is 10 to 3
0 at%, Pt 4 to 18 at%, B 0.5 to 15 a
The composition range is t% and the balance is Co.

The protective layer 7 is for preventing the magnetic layer from deteriorating due to contact with the magnetic head, and is composed of a hydrogenated carbon film having a film thickness of 45 angstrom. The lubricating layer 8 is made of a liquid lubricant of perfluoropolyether, and this film alleviates the contact with the magnetic head. The film thickness is 8 Å.

Next, a method of manufacturing the magnetic recording medium having the above structure will be described. First, precision polishing the main surface of the glass substrate chemically strengthened by low temperature ion exchange,
The center line average roughness Ra is finished to 0.2 nm.

Next, a precoat layer 2 made of a CrMo thin film and a NiP type alloy layer 3 made of a NiP thin film are formed by a static opposed sputtering apparatus.

Next, a tape-type texture device is used to form concentric circular textures (grooves) on the surface of the NiP alloy layer 3 (maximum height Rmax = 3.5 nm, pitch 0.025 μm).

FIG. 2 is a schematic view of a tape type texture device used in the first embodiment. As shown in FIG. 2, in the tape-type texture device used in this embodiment, the glass substrate 1 fixed to the spindle 101 is rotated, and the polishing agent is supplied to the tape 103 from the slurry dropping port 102, so that the glass substrate By sandwiching both main surfaces of No. 1 with the tape 103 wound around the roller 104, concentric grooves are formed on the main surface of the glass substrate 1. Tape 1
The roller 104 wound with 03 is rotating at a constant rotation speed so that the new surface of the tape 103 is always in contact with the substrate. In this case, by swinging the spindle 101, a cross texture or a spiral shape can be prepared.

Next, CrM was formed on the main surface of the substrate with the NiP alloy layer by a static facing type sputtering device.
o Underlayer 4 made of a thin film, intermediate layer 5 made of a CoCr thin film, CoCrPtB magnetic layer 6, hydrogenated carbon protective layer 7
Were sequentially formed. The base layer 4 and the magnetic layer 6 were applied with a bias voltage of -300 V, and the protective layer 7 was A.
In a mixed gas atmosphere of r + H ₂ , other layers are Ar
Under an inert gas atmosphere, the film was formed by sputtering at a substrate heating temperature of 200 ° C. Then, the protective layer 7 was dip-treated with a perfluoropolyether lubricant to form a lubricating layer 8 to obtain a magnetic disk.

Coercive force Hc of the obtained magnetic disk
Is 3526 Oe, and the coercive force squareness ratio S * is 0.77.
, The solitary wave reproduction output LF is 1.521 mV, the solitary wave pulse width PW is 13.77 nsec, and the S / N ratio is 2.
9.27 dB, which is the ratio of the coercive force in the circumferential direction to the coercive force in the radial direction, OR (Oriented Ratio)
Was 1.21. Thus, it can be seen that it has an extremely high S / N ratio as compared with the comparative example described later.

This is because concentric circular textures (grooves) formed on the surface of the non-magnetic substrate improve the in-plane orientation of the magnetic layer, and unevenness of the texture reduces the size distribution of magnetic particles. It is considered that the characteristics of are improved. Further, in this case, the size of the crystal grains of the CrMo underlayer 4 was 130Å (measured by a TEM (transmission electron microscope)). The size of the crystal grains of the CrMo underlayer 4 is
It is preferably 50 Å or more and less than 140 Å, more preferably 60 Å or more and 130 Å or less. Furthermore, CrM
o The thickness of the underlayer 4 is preferably 80 Å or more and less than 300 Å. If it is less than 80 Å, the orientation of the magnetic layer formed on it deteriorates, so the coercive force Hc and the coercive force squareness S
*, Output LF, pulse width PW, and S / N ratio deteriorate. Three
When it exceeds 00Å, the coercive force Hc is good, but the S / N ratio is greatly deteriorated because the size of the crystal grain is large, which is not preferable.

The characteristics of the coercive force Hc, the coercive force squareness ratio S *, the solitary wave reproduction output LF, the solitary wave pulse width PW, and the S / N ratio are measured as follows. Other Examples and Comparative Examples described later were also measured by the same measuring method.

The coercive force Hc and the coercive force squareness ratio S * are determined by a vibrating sample magnetometer (VSML: Vibrating S).
The measurement was carried out using an ample Magnetometer).
The higher the coercive force Hc, the better the PW and the improvement of thermal fluctuation characteristics. The coercive force squareness ratio S * is an index representing the in-plane orientation and the magnetic separation between magnetic grains, and the higher the better.

The solitary wave reproduction output LF was measured by an electromagnetic conversion characteristic measuring instrument (Guzik). Solitary wave reproduction output LF
If the other electromagnetic conversion characteristics can be maintained, the reproduction output of the recording signal becomes high, so the higher the better.

The solitary wave pulse width (PW50: half-value width of solitary signal waveform) was measured as follows. An isolated reproduction signal was extracted with an electromagnetic conversion characteristic measuring instrument (Guzik) equipped with an MR head, and the width of the isolated waveform at 50% of the peak value of the output signal with respect to the ground (0) was defined as PW50. It should be noted that the smaller the PW50, the better for high recording density. This is because if the pulse width is narrow, more pulses (signals) can be written on the same area. On the other hand, if the PW50 is large, adjacent pulses (signals) interfere with each other, and an error appears when reading the signals. This waveform interference deteriorates the error rate.

The S / N ratio was measured using an electromagnetic conversion characteristic measuring instrument (Guzik). The magnetic head used for the measurement is
GMR (Giant Magnet) with a flying height of 20 nm
Resistor: A head (hereinafter referred to as a GMR head) having a reproducing element of giant magnetoresistive type. The recording track width is 2.0 nm and the reproducing track width is 0.
It is 5 nm. The S / N ratio is the IF recording density (520 kf
After recording a carrier signal on the magnetic recording medium in step ci), the medium noise from the DC frequency region to the 1.2 times the IF frequency region was observed and calculated using a spectroanalyzer. Generally, if the S / N ratio is improved by 0.5 dB, it can contribute to the improvement of the recording density of ² Gbit / inch ² . The higher the S / N ratio is, the more the error rate is improved and the high density recording can be achieved in order to prevent a signal reading error due to noise.

(Comparative Example 1) Next, the underlayer made of the CrMo thin film in the magnetic recording medium of Example 1 was replaced with CrW.
A magnetic recording medium was manufactured in the same manner as in Example 1 except that (W: 10 at%) was changed to Comparative Example 1. The coercive force Hc of the obtained magnetic recording medium of Comparative Example 1 was 3510.
Oe, coercive force squareness ratio S * is 0.82, solitary wave reproduction output L
F is 1.520 mV and solitary wave pulse width PW is 13.89.
nsec, S / N ratio is 27.28 dB, OR is 1.19
Met. It can be seen that the S / N ratio is inferior as compared with Example 1.

Further, CrMo9 (Mo: 9 at%) of the underlayer in the recording medium of Example 1 was replaced with CrMo5 (M
o: 5 at%) except that the magnetic recording medium manufactured in the same manner as in Example 1 was used as Example 2, and CrMo9 was used as C
A magnetic recording medium manufactured in the same manner as in Example 1 except that the content was changed to rMo30 (Mo: 30 at%) was set as Example 3. FIG. 3 is a table showing the characteristics of the examples and the like.

As shown in the table of FIG. 3, M of CrMo is
When the o concentration is 5 to 30 at%, the characteristics hardly change. However, when the Mo concentration is extremely low (<5 at
%), The lattice deviation between the CrMo underlayer and the magnetic layer increases, and the characteristics deteriorate. Also, when the Mo concentration is extremely high, the characteristics are significantly deteriorated due to the lattice shift. Therefore, the Mo concentration is preferably 5 to 30 at%.

Example 4 A magnetic recording medium was prepared in the same manner as in Example 1 except that the material of the precoat layer 2 in Example 1 was changed from CrMo alloy to NiAl alloy.
It was set as Example 4. Coercive force H of the obtained magnetic disk
c is 3512 Oe, coercive force squareness ratio S * is 0.79, solitary wave reproduction output LF is 1.524 mV, and solitary wave pulse width P.
W is 13.87 nsec, S / N ratio is 29.23 dB,
The OR was 1.20.

(Fifth Embodiment) FIG. 4 is a diagram showing the structure of a magnetic recording medium according to the fifth embodiment. In this embodiment, the texture 11 is directly formed on the surface of the non-magnetic substrate (glass substrate) 1. That is, a concentric texture (maximum height Rmax = 3.4 nm, on the surface of the glass substrate 1 using the same texture device as in Example 1 above,
The pitch in the radial direction is 0.025 μm), and the precoat layer 2 is formed by using a stationary facing sputtering device.
Magnetic recording was performed in the same manner as in Example 1 except that the NiP-based alloy layer 3 was formed and the underlayer 4, the intermediate layer 5, the magnetic layer 6, the protective layer 7, and the lubricating layer 8 were further formed as in Example 1. A medium is produced. Coercive force H of the obtained magnetic disk
c is 3434 Oe, coercive force squareness ratio S * is 0.75, solitary wave reproduction output LF is 1.487 mV, solitary wave pulse width P
W is 13.99 nsec, S / N ratio is 28.87 dB,
The OR was 1.07.

Reference Examples 1 and 2, Examples 1 and 6 to 8 Next, the bias voltage in Example 1 is 0 V (Reference Example 1), -100 V (Example 6), and -200 V (Example 7). , -300V (Example 1), -400V (Example 8), and -500V (Reference Example 2) except that the magnetic recording medium was manufactured in the same manner as in Example 1 to obtain PW and S / N.
Ratio characteristics were measured. FIG. 5 is a graph showing changes in characteristics of PW and S / N ratio due to differences in bias voltage. As shown in FIG. 5, the bias voltage is set to −100V to −400.
It can be seen that a high S / N ratio is obtained when the film is formed at V, which is preferable.

FIG. 6 is a graph showing the S / N ratio measured by changing the film thickness of the magnetic layer when the composition of the underlayer is changed. In FIG. 6, the vertical axis represents the S / N ratio value and the horizontal axis represents the output (LF) value. Since the output (LF) value changes when the film thickness of the magnetic layer is changed, the output (LF) is shown instead of the film thickness. The plot points marked with X show the measured values of the S / N ratio when the underlayer is made of a CrMo alloy having a Mo concentration of 9 at% and the thickness of the magnetic layer is variously changed. Similarly, the black square plot points indicate that the underlayer is made of a CrMo alloy having a Mo concentration of 12 at%, and the black rhombus plot points indicate the underlayer by M
In the case of the CrMo alloy having an o concentration of 15 at%, the black triangle plot points indicate the case where the underlayer is made of a CrW alloy having a W concentration of 20 at%.

From FIG. 6, the S / N ratio of the underlayer made of a CrMo alloy is much higher than that of a CrW alloy.
The ratio is good, and when composed of CrMo alloy, M
It can be seen that the o concentration is preferably 12 at% rather than 15 at%, and 9 at% is better than 12 at%.

[0051]

As described above, according to the present invention,
A concentric texture is formed on either or both of the surface of the non-magnetic substrate and the surface of the layer formed between this substrate and the magnetic layer, and the underlayer is made of a CrMo-based alloy, and the thickness of the layer. Has a high coercive force and an S / N ratio of 80 to 300Å, or the size of the crystal grains of the CrMo-based alloy constituting the underlayer is less than 140Å, or the magnetic layer is composed of a CoCrPtB-based alloy. The ratio makes it possible to obtain a good magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a diagram showing a film configuration of a magnetic recording medium according to a first embodiment.

FIG. 2 is a schematic diagram of a tape-type texture device used in the first embodiment.

FIG. 3 is a table showing characteristics of examples and the like.

FIG. 4 is a diagram showing a structure of a magnetic recording medium according to a fifth embodiment.

FIG. 5 is a graph showing characteristic changes in PW and S / N ratio due to differences in bias voltage.

FIG. 6 is a graph showing the S / N ratio measured by changing the film thickness of the magnetic layer when the composition of the underlayer is changed.

[Explanation of symbols]

1 ... Non-magnetic substrate, 11, 31 ... Texture, 2 ... Precoat layer, 3 ... NiP type alloy layer, 4 ... Underlayer, 5 ... Intermediate layer, 6 ... Magnetic layer, 7 ... Protective layer, 8 ... Lubricating layer.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisao Kawai             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. (72) Inventor Teichiro Umezawa             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. (72) Inventor Hirotaka Tanaka             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. (72) Inventor Masaki Uemura             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. F-term (reference) 5D006 BB02 CA01 CA05 CA06 CB04                       CB07 CB08 EA03 EA05                 5D112 AA02 AA03 BA03 BA05 FA04                       GA09

Claims (8)

[Claims] 1. A Cr-based underlayer and CoP on a non-magnetic substrate.
A magnetic recording medium having a t-based magnetic layer, wherein the in-plane orientation of the magnetic layer is on either or both of the surface of the non-magnetic substrate and the surface of the layer formed between the substrate and the magnetic layer. Magnetic recording layer having a concentric circular texture for improving the magnetic property, wherein the Cr-based underlayer is a CrMo-based alloy containing Cr and Mo, and the thickness of the layer is 80 to 300Å. Medium. 2. A Cr-based underlayer and CoP on a non-magnetic substrate.
A magnetic recording medium having a t-based magnetic layer, wherein the in-plane orientation of the magnetic layer is on either or both of the surface of the non-magnetic substrate and the surface of the layer formed between the substrate and the magnetic layer. A concentric circular texture for improving the property is formed, and the Cr-based underlayer is a CrMo-based alloy containing Cr and Mo, and the size of the crystal grains of the CrMo-based alloy constituting the layer is less than 140Å. A magnetic recording medium characterized by the above. 3. The CoPt-based magnetic layer is CoCrPt.
The magnetic recording medium according to claim 1, which is a B-based magnetic layer. 4. The non-magnetic substrate is a glass substrate, and the concentric circular texture is formed on a surface of a NiP-based alloy layer formed on the glass substrate. 4. The magnetic recording medium according to any one of 3 to 3. 5. The magnetic recording medium according to claim 1, wherein the CrMo-based alloy forming the underlayer has a Mo content of 5 to 30 at%. 6. The NiP-based alloy layer is formed by sputtering, and the non-magnetic substrate and the N
6. A precoat layer that improves the film adhesion between the non-magnetic substrate and the NiP alloy layer is formed between the iP alloy layer and the iP alloy layer. Magnetic recording medium. 7. The precoat layer comprises Cr, a Cr alloy,
7. The magnetic recording medium according to claim 6, which is made of a material selected from NiAl. 8. The magnetic recording according to claim 1, wherein at least the underlayer is formed by sputtering by applying a negative bias voltage of −100V to −400V. Medium.