JP2003217110A - Magnetic disk and magnetic disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk device and a magnetic disk for solving the problem that reliability of a magnetic disk device is reduced due to a so- called later occurring error. <P>SOLUTION: In the magnetic disk on the surface of which a liquid lubricant having a perfluoropolyether structure is applied, the magnetic disk is so constituted that a lubrication film on a protective film contains at least one lubricant component having a structure represented by formula (1) (wherein p= an integer of 0 or 1 or more; q= an integer of 0 or 1 or more and X=1 to 5) or formula (2) (wherein p= an integer of 0 or 1 or more; q= an integer of 0 or 1 or more and X=1 to 5) and a lubricant except the lubricant, which has a structure represented by formula (3) (wherein p= an integer of 0 or 1 or more and q= an integer of 0 of 1 or more) and whose average molecular weight and ratio to the whole lubrication film are 600 to 2,400 and ≤50%, respectively. <P>COPYRIGHT: (C)2003,JPO

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 in which at least a magnetic film and a protective film are formed on a non-magnetic magnetic disk substrate and a liquid lubricant having a perfluoropolyether structure is applied to the surface thereof. Regarding Further, a magnetic head and a magnetic disk for recording / reproducing, a mechanism for rotating the magnetic disk, a mechanism for positioning the magnetic head, a circuit for processing a recording / reproducing signal, and a mechanism for supplying a lubricant into the magnetic disk device as a gas are provided. The present invention relates to a magnetic disk device having the same.

[0002]

2. Description of the Related Art The recording density of a magnetic disk device is increasing remarkably, and recently, the recording density per square inch is 20.
More than gigabit have been announced. In order to achieve such a high recording density, it is essential to make the distance between the magnetic head and the magnetic recording layer of the magnetic disk as close as possible, and it is currently a situation where it should be 20 nm or less.

In the recent magnetic disk apparatus, the surface roughness of the magnetic disk has to be made as small as possible in order to make the distance as close as possible, so that the magnetic head is stopped when the rotation of the conventional magnetic disk is stopped. From the contact start stop method in which the magnetic head floats due to the air flow when the magnetic disk starts contacting and the magnetic disk starts to rotate, the magnetic head is retracted (unloaded) from the magnetic disk when the magnetic disk is stopped, A load / unload method is being adopted in which the magnetic head is loaded on the magnetic disk when the magnetic disk starts to rotate. In this case, the sliding resistance is slightly relaxed, but it is necessary to withstand a shock at the time of load-on and a contact due to an abnormal posture of the magnetic head that may suddenly occur during normal operation.

In order to reduce the wear and damage caused by the contact between the head and the magnetic disk, improvement of the protective film of the magnetic disk or improvement of the lubricating film has been advanced. For example, in order to improve the performance of a lubricant, use of a perfluoropolyether having a phosphazene ring group as a lubricant, as described in JP-A-8-319491, and JP-A-10-143836. As described above, a lubricating film in which polyphenoxy-cyclotriphosphazene is mixed with perfluoropolyether in a proportion of 0.01 to 1 by weight, and JP-A 2001-1877.
As described in 96, a lubricating film containing 30% or more of perfluoropolyether having a phosphazene ring group has been proposed. These techniques are aimed at improving the wear resistance of the magnetic disk, reducing the contamination of the head, reducing the frictional force, and reducing the decomposition of the lubricant. However, combinations of these phosphazene-containing lubricants with other lubricants to be mixed are not disclosed in detail. In particular, when two kinds of lubricants are mixed and used, it is necessary to consider the combination at least from the viewpoints of compatibility of the lubricants, head contamination, frictional force and the like.

Regarding the decomposition of the lubricant, it is considered that hydrogen fluoride (HF) is generated by thermal decomposition by frictional heat or decomposition by Lewis acid, and the lubricant is decomposed in a chain by the HF. Japanese Unexamined Patent Publication No. 10-143839 discloses that a lubricant is decomposed by exoelectrons generated during friction between a magnetic head and a magnetic disk.

The technique of supplying the lubricant as a gas into the magnetic disk drive has been to arrange a lubricant supply source in the head disk assembly. The purpose of supplying the lubricant is to reduce the scattering of the lubricant due to rotation and heat. In the conventional example, the material of the lubricant to be supplied, the adsorption property and the material of the lubricating film formed on the magnetic disk, the adsorption property and the combination thereof are not taken into consideration. In some cases, reliability could not be improved even if supplied to the head disk interface. Further, depending on the lubricant used for supply, it is impossible to prevent the magnetic head from being soiled, which causes a decrease in reliability. Further, depending on the lubricant used for supply, corrosive outgas in the magnetic disk device adheres to and deposits on the magnetic head element portion, causing a problem of corroding the metal of the element portion. Further, the adsorptivity of the lubricant differs depending on the type and film quality of the protective film of the magnetic disk. Particularly in the case of diamond-like carbon (DLC) film, the adsorptivity of the lubricant is smaller than that of the carbon film formed by sputtering, so that the lubricant film of the magnetic disk and the lubricant attached to the magnetic disk are both retained on the magnetic disk. There is a problem that it is hard to be done and wear resistance deteriorates.

A magnetic head used for a magnetic disk is generally composed of a reproducing element utilizing a magnetoresistive effect and a magnetic induction type recording element. The recording element is composed of a coil for generating a magnetic field and a magnetic pole for guiding the magnetic field, and a current of about several tens mA is passed through the coil to record a signal. A bias current is applied to the reproducing element, and a signal is reproduced by detecting a resistance change due to a magnetic field. This bias current is a few mA
~ A few 10mA. It is clear that the recording / reproducing frequency increases with the recording density, and the recording density is 20 Gbit / inch ²
Approximately 300MH for 3.5 inch magnetic disk unit
reach z When recording at such a high frequency, the recording element generates heat due to electric resistance and impedance resistance and becomes extremely high in temperature. This heat generation amount varies depending on the element structure of the head, but when it is high, it may reach 200 to 250 ° C., and the higher the recording frequency, the larger the heat generation amount. Similar heat is generated in the reproducing element. Since the reproducing element has a film thickness on a submicron scale and the track width becomes narrower with the recording density, the amount of heat generated increases with the recording density.

[0008]

It is easily inferred from the prior art that the lubricant of the magnetic disk is decomposed by frictional heat. However, it is clear from the prior art that the reliability of the magnetic disk device decreases due to the decomposition of the lubricant adhering to the slider surface near the recording / reproducing element of the head due to the heat generated by the recording / reproducing element of the head. It hasn't been. In the process of investigating the cause of the decrease in reliability of the magnetic disk device, we have found that the decomposition or transfer of the lubricant due to the heat generation of the head recording / reproducing element causes the decrease in reliability.

Further details will be described. The lubricant adhering to the slider surface in the vicinity of the recording / reproducing element is decomposed by the heat generation of the recording / reproducing element to generate hydrogen fluoride (HF),
The lubricant having a high HF concentration adheres to the magnetic disk surface. The lubricant attached to the surface of the magnetic disk corrodes the magnetic film of the magnetic disk and the like, and the surface of the magnetic disk to which the lubricant whose volume is expanded due to the corrosion is attached becomes a protrusion. The magnetic disk surface to which the lubricant that has become a protrusion adheres to the magnetic head and wears the protective film and magnetic film, and in the worst case, the data recorded on the magnetic film will be lost Causes an error called an error.

The present invention provides a magnetic disk device and a magnetic disk for solving the problem that the reliability of the magnetic disk device is lowered due to the occurrence of the subsequent error.

[0011]

PROBLEM TO BE SOLVED: To protect a magnetic disk in which at least a magnetic film and a protective film are formed on a non-magnetic magnetic disk substrate and a liquid lubricant having a perfluoropolyether structure is applied to the surface thereof. The lubricating film on the film contains at least one lubricant component having the structure represented by the chemical formula (1) or (2), and has the structure represented by the chemical formula (3) and has an average molecular weight of 2400 or less and 600 or more. The magnetic disk is configured so that the ratio of the lubricant component is 50% or less with respect to the entire lubricant film.

[0012]

[Chemical 1]

Here, p = 0 or an integer of 1 or more, q = 0 or an integer of 1 or more, and X = 1 to 5.

[0014]

[Chemical 2]

Here, p = 0 or an integer of 1 or more, q = 0 or an integer of 1 or more, and X = 1 to 5.

[0016]

[Chemical 3]

Here, p = 0 or an integer of 1 or more and q = 0 or an integer of 1 or more.

Further, a magnetic head and a magnetic disk for recording / reproducing, a mechanism for rotating the magnetic disk, a mechanism for positioning the magnetic head, a circuit for processing a recording / reproducing signal, and a lubricant for supplying gas into the magnetic disk device. In the magnetic disk device having the above mechanism, the magnetic disk has at least a magnetic film and a protective film formed on a non-magnetic magnetic disk substrate, and the surface thereof is coated with a liquid lubricant having a perfluoropolyether structure. The lubricant film on the protective film is made of a lubricant having the structure represented by the chemical formula (1) or the chemical formula (2), and the lubricant supplied from the mechanism for supplying the lubricant into the magnetic disk device is the chemical formula. It has the structure described in (3) and has an average molecular weight of 2400.
This is achieved by configuring the magnetic disk device so that it is 600 or more.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The effects of the present invention will be described below based on Examples. As the non-magnetic magnetic disk substrate, a glass substrate commercially available for magnetic disks is preferably used. The surface roughness of the magnetic disk medium surface reflects the surface roughness of the substrate surface.
What was set to nm was prepared.

<Embodiment 1> FIG. 1 shows a schematic view of a film structure of a magnetic disk of Embodiment 1. After cleaning the above-mentioned glass substrate 1, a seed film (2), a base film (3) and a lower magnetic film shown in the figure are formed on the glass substrate 1 by using a single-wafer sputtering apparatus (MDP-250 manufactured by Intevac Co., Ltd.). A film (4), a non-magnetic intermediate film (5), an upper magnetic film (6) and an amorphous carbon film (7) were formed. The seed film (2) is sputtered using a NiTa alloy target and has a film thickness of 30 nm. The film thickness of the seed film was measured and determined by a fluorescent X-ray measurement method. After forming the seed film, heat it to 260 ℃, and then add it to Ar-O2 mixed gas.
Exposed for 3.5 seconds. Then, the CrTi alloy underlayer film (3) is 5 nm on the seed film, the CoCrPt alloy magnetic film is 3.5 nm as the lower magnetic layer (4), Ru is 0.5 nm as the intermediate film (5), and CoCrPtB is the upper magnetic film (6). An alloy film having a thickness of 15 nm was formed. A nitrogen-containing carbon protective film (7) is provided on the upper magnetic film.
5 nm was formed. The protective film may be a DLC (diamond-like carbon) film formed by a CVD (chemical vapor deposition) method or an IBD (ion beam deposition) method. For the film thickness of the protective film, use the X-ray reflection method,
In order to improve the accuracy of film thickness measurement, Cr was deposited to a thickness of 5 nm on the protective film and quantified. The quantification of the film thickness by the X-ray reflection method was carried out using SLX2000 ^™ manufactured by Rigaku Denki Kogyo Co., Ltd. using X-rays of Cu K _α1 . On the protective film, HFE710 made by Sumitomo 3M
A solution of the lubricant represented by the chemical formula (1) was prepared using 0 as a solvent, and a magnetic disk was dipped in the lubricant solution to form a lubricating film 8. The number average molecular weight of the main chain portion of the perfluoropolyether of the lubricant of the chemical formula (1) is 2000. The lubricating film thickness was 1.5 nm as measured by FTIR.

Example 2 A magnetic disk was manufactured in the same manner as in Example 1. However, the lubricant represented by the chemical formula (2) was used. The number average molecular weight of the perfluoropolyether main chain portion of the lubricant of the chemical formula (2) is 2000. The lubricating film thickness was 1.5 nm as measured by FTIR.

<Comparative Example 1> A magnetic disk was manufactured in the same manner as in Example 1. However, the lubricant was a lubricant represented by the chemical formula (3), and four types of lubricants having a number average molecular weight of 1000, 2000, 3000, 4000, 6000 determined by an NMR (nuclear magnetic resonance) method were used. Lubricant thickness measured by FTIR is 1.5n each
It was m.

The magnetic disks of Examples 1 and 2 and Comparative Example 1 were
It was incorporated into a 3.5-inch magnetic disk unit. A schematic diagram of the magnetic disk device is shown in FIG.

Spindle 1 for rotating magnetic disk 9
0, an arm 12 for holding the magnetic head 11, a voice coil motor 13 for positioning the arm 12, a circuit 14 for processing a signal, a mechanism for supplying a lubricant into the apparatus (a dust filter 15 in this case), and the like. . In order to supply the lubricant into the magnetic disk device, the magnetic filter is represented by the chemical formula (3) on the dust filter inside the magnetic disk device, and 1.0 mg of the lubricant having a number average molecular weight of 2000 is dropped and placed in a predetermined position. A disk device was prepared and examples and comparative examples were incorporated. The rotation speed of the magnetic disk device is 10,000 rotations / minute, the recording density is about 20 Gbit / inch 2, the flying height of the head is about 15 nm, and the test environment temperature is 50 ° C.

Then, the radial position of the head was fixed at 38 mm in the magnetic disk device, and the recording was continuously followed by fixed recording tracks to monitor the number of subsequent errors. The result is shown in FIG.

As is clear from FIG. 3, no subsequent error occurred in Examples 1 and 2, but in Comparative Example 1, the number of subsequent errors increased with time. Thus, the magnetic disk coated with the perfluoropolyether lubricant having the molecular structure represented by the chemical formulas (1) and (2) is placed in the magnetic disk device and the number average molecular weight represented by the chemical formula (3) is
The use of 2000 in a magnetic disk device having a mechanism for supplying a lubricant reduces the occurrence of subsequent errors and improves the reliability of the magnetic disk device.

After the magnetic disk device was operated for 465 hours, it was disassembled and the lubricating film thickness of the incorporated magnetic disk was measured.
It was measured by FTIR. The change in the lubricating film thickness before and after the test is shown in FIG.

For example, the lubricating film thickness of the magnetic disk of Example 1 was initially 1.5 nm, but increased to 1.8 nm after the test. This is because the lubricant in the magnetic disk device increased by adhering to the magnetic disk, and by supplying the lubricant into the device, it is possible to eliminate the decrease in the lubricant on the magnetic disk due to rotation and heat. It is shown that. From this result, it can be assumed that the lubricant represented by the chemical formula (1) is present in the lubricant film of the magnetic disk at a ratio of 1.5 nm and the lubricant represented by the chemical formula (3) is present at a ratio of 0.3 nm. . In this case, the lubricant of chemical formula (1) is 83
It is defined as existing as a percentage. The numerical values shown in FIG. 4 indicate the proportion of the lubricant on the magnetic disk before the test. After the test, the ratio of the lubricant of the magnetic disk before the test was 70 to 90% in each of Examples 1 and 2 and Comparative Example 1. From this result, the lubricating film of the magnetic disk before the test was tested as a mixed film of the lubricant represented by the chemical formulas (1) and (2) and the lubricant represented by the chemical formula (3) and having the number average molecular weight of 2000. It can be understood that the frequency of occurrence of the subsequent error can be reduced if the mixing ratio of the subsequent lubricating film is the same.

Example 3 A magnetic disk was manufactured in the same manner as in Example 2. Lubrication film thickness is 1.5 nm as measured by FTIR
Met. This magnetic disk was incorporated into a 3.5-inch magnetic disk device. The magnetic disk device is represented by the chemical formula (3) in the dust filter in the magnetic disk device in order to supply the lubricant into the device, and 1.0 mg of the lubricant having the number average molecular weight of 1000 and 2000 is dropped on each filter and predetermined. Two kinds of magnetic disk devices arranged at the position of 2 were prepared and the magnetic disk of Example 3 was incorporated. The test method is the same as in Examples 1 and 2.

<Comparative Example 2> A magnetic disk was prepared in the same manner as in Example 3. However, the lubricant to be supplied into the device is represented by the chemical formula (3) and has a number average molecular weight of 3000, 4000, 60.
Three kinds of magnetic disk devices were prepared by dropping 1.0 mg of each of them as a lubricant of 00 onto each filter and arranging them at predetermined positions, and the magnetic disk of Comparative Example 2 was incorporated. The test method is the same as in Examples 1 and 2.

The test results of Example 3 and Comparative Example 2 are shown in FIG.

From the results of this test, it has been found that the frequency of occurrence of subsequent errors increases as the molecular weight of the lubricant supplied increases. Figure 5 is rewritten using the molecular weight of the lubricant as a parameter.

As is clear from FIG. 6, the molecular weight is small, and particularly when the molecular weight is 2400 or less, the occurrence of subsequent errors is small. Also,
If the molecular weight is too small, it may not function as a lubricant due to an excessively large amount of evaporation, and therefore the average molecular weight is preferably 600 or more. From the test results of Examples 1, 2, and 3 and Comparative Examples 1 and 2, the lubricant supplied into the magnetic disk device is represented by the chemical formula (3), and the number average molecular weight is 600 or more and 2400 or less,
Since the lubricating film formed on the magnetic disk is composed of the lubricant of chemical formula (1) or chemical formula (2), a highly reliable magnetic disk device can be obtained.

Next, the lubricating film thickness of the magnetic disk device of Example 3 after the test was measured. The magnetic disk incorporated in the magnetic disk device supplied with a lubricant having a molecular weight of 1000 had a lubricating film thickness of 1.75 nm and a molecular weight. The lubrication film thickness of the magnetic disk incorporated in the 2000 magnetic disk device was 1.86 nm. From this result, it was found that the proportions of the lubricant component of the chemical formula (2) were 86% and 81%, respectively. That is, it is considered that the magnetic disk having the lubricant film in which the lubricant represented by the chemical formula (3) and having the average molecular weight of 600 to 2400 is mixed with the lubricant represented by the chemical formula (1) or (2) has less occurrence of the subsequent error.

<Example 4> A magnetic disk was manufactured in the same manner as in Example 2. However, the lubricating film thickness is 1.0, 1.2, 1.5, 1.8 nm
I adjusted it to be.

<Comparative Example 3> A magnetic disk was manufactured in the same manner as in Example 2. However, the lubricating film thickness was adjusted to 0.4, 0.6 and 0.8 nm.

The magnetic disks of Example 4 and Comparative Example 3 were incorporated in different 3.5-inch magnetic disk devices. In order to supply the lubricant into the magnetic disk device, the dust filter in the magnetic disk device is represented by the chemical formula (3), and the lubricant having the number average molecular weight of 1000 and 2000 is dropped 1.0 mg each. Prepared and incorporated the examples and comparative examples. The rotation speed of the magnetic disk device is 10,000 rotations / minute, the recording density is about 20 Gbit / inch 2, the flying height of the head is about 15 nm, and the test environment temperature is 50 ° C. After the test was performed for 500 hours, the numbers of subsequent errors were compared. Further, the lubricating film thickness before and after the test was compared.

FIG. 7 shows a comparison of the lubricating film thickness before and after the test, and FIG. 8 shows the relationship between the ratio of the lubricant represented by the chemical formula (2) of the lubricating film after the test and the number of subsequent errors.

It can be seen from FIG. 7 that the lubricating film thickness after the test increases from the initial value and does not depend on the initial lubricating film thickness.
It is about m, and the smaller the initial film thickness, the smaller the proportion of the lubricant of the chemical formula (2). Also, FIG.
From the results, it was found that the ratio of the chemical formula (2) was 50% or more, that is, the ratio of the lubricant of the chemical formula (3) was 50% or less, and no subsequent error occurred. From these results, the lubricant of the chemical formula (1) or (2) and the lubricant of the chemical formula (3) are used as the lubricating film of the magnetic disk and the average molecular weight is 600 or more 2400.
The following lubricants are included, and when the proportion of the lubricant of the chemical formula (3) is 50% or less, it is possible to obtain a highly reliable magnetic disk in which a subsequent error does not occur.

<Comparative Example 4> A magnetic disk was prepared in the same manner as in Example 1. However, as the lubricant, 70% of the lubricant represented by the chemical formula (2) and 30% of the lubricant represented by the chemical formula (4) and having an average molecular weight of 3000 were applied to the magnetic disk. The lubricating film thickness at this time was 1.5 nm. This magnetic disk has a structure of chemical formula (4) and an average molecular weight of 20.
A follow-up test was carried out by incorporating it into a magnetic disk having a mechanism for supplying 00 lubricant, and the occurrence of subsequent errors was investigated.

[0041]

[Chemical 4]

As a result, the number of subsequent errors was 24 after the test time of 500 hours, which was inferior in reliability to the magnetic disk shown in the embodiment. That is, the average molecular weight of the lubricant of chemical formula (1) or (2) and the structure of chemical formula (3) is 60
It is considered that the subsequent error does not occur only in combination with the lubricant of 0 to 2400 and only when the proportion of the lubricant of the chemical formula (1) or (2) is 50% or more.

The molecular weight of the main chain portion of the lubricant of the chemical formula (1) or (2) applied to the magnetic disk is 20 in the examples.
Although the one of 00 was used, it is not limited to this molecular weight, and the same effect can be obtained as long as the lubricant has an average molecular weight of about 1500 to 6500. Generally, the larger the molecular weight of the lubricant is, the less the aggregation of the lubricating film is. Therefore, it is considered that a high molecular weight, that is, a molecular weight of about 3500 to 5500 is suitable for stable floating of the head.

As shown in the embodiment, a mixed lubricant film of the lubricant represented by the chemical formula (1) or (2) and the lubricant represented by the chemical formula (3) and having an average molecular weight of 600 to 2400 is used in the chemical formula (3).
By making the magnetic disk with the ratio of the lubricant of 50% or less, it is suitable for the magnetic disk device having a mechanism for supplying the lubricant having the average molecular weight of 600 to 2400 represented by the chemical formula (3) into the device, The reliability of the disk device is significantly improved.

[0045]

According to the present invention, the thickness of the protective film is 1.0 to 5.0 nm.
It is possible to realize excellent recording / reproducing capability, dust resistance and abrasion resistance in the magnetic disk having the ultra-thin protective film.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a magnetic disk according to a first embodiment of the invention.

FIG. 2 is a structural schematic diagram of a magnetic disk device.

FIG. 3 is a diagram comparing the numbers of subsequent errors with respect to the following times of Examples 1 and 2 and Comparative Example 1.

FIG. 4 is a diagram comparing the lubricating film thicknesses of Examples 1 and 2 and Comparative Example 1 before and after the test.

FIG. 5 is a diagram comparing the number of subsequent errors with respect to the following time in Example 3 and Comparative Example 2.

FIG. 6 is a graph showing the dependence of the number of subsequent errors on the molecular weight.

FIG. 7 is a diagram comparing the lubricating film thickness of Example 4 and Comparative Example 3 before and after the test.

FIG. 8 is a diagram showing a relationship between a ratio of the lubricant of chemical formula (1) and a subsequent error.

[Explanation of symbols]

1 --- non-magnetic substrate, 2 --- seed film, 3 --- base film, 4 --- lower magnetic film, 5 --- non-magnetic intermediate layer, 6 ---- upper magnetic film, 7-- -Protective film, 8--Lubrication film, 9 --- Magnetic disk, 10 --- Spindle motor, 11 --- Magnetic head, 12 --- Arm, 13 --- Voice coil motor, 14 --- Signal processing circuit, 15 --- dust filter

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C10M 107/48 C10M 107/48 // C10N 20:04 C10N 20:04 40:18 40:18 (72) Inventor Mitsuhiro Masada 2880, Kozu, Odawara, Kanagawa, Ltd.Hitachi, Ltd. Storage Division (72) Inventor Koji Sonoda, 2880, Kozu, Odawara, Kanagawa, Ltd., Hitachi, Ltd., Storage Division (72) Takayuki Nakagawa, Ibaraki 7-1-1 Omika-cho, Hitachi City, Hitachi Prefecture F-term in Hitachi Research Laboratory, Hitachi, Ltd. (reference) 4H104 BH14A CE19A EA03A PA16 4J005 AA02 AA09 BD05 BD07 5D006 AA01 DA03 EA03 FA09

Claims (2)

[Claims] 1. At least a non-magnetic magnetic disk substrate,
In a magnetic disk in which a magnetic film and a protective film are formed and a liquid lubricant having a perfluoropolyether structure is applied to the surface thereof, the lubricating film on the protective film is represented by the chemical formula (1) or the chemical formula (2). At least one lubricant component having the structure of No. 2 and having the average molecular weight of 2400 or less and 600 or more and having the structure represented by the chemical formula (3) in a proportion of 50% or less with respect to the entire lubricating film. A magnetic disk characterized by. [Chemical 1] Here, p = 0 or an integer of 1 or more, q = 0 or an integer of 1 or more, and X = 1 to 5. [Chemical 2] Here, p = 0 or an integer of 1 or more, q = 0 or an integer of 1 or more, and X = 1 to 5. [Chemical 3] Here, p = 0 or an integer of 1 or more, and q = 0 or an integer of 1 or more. 2. A magnetic head and a magnetic disk for recording / reproducing, a mechanism for rotating the magnetic disk, a mechanism for positioning the magnetic head, a circuit for processing a recording / reproducing signal, and supplying a lubricant as a gas into the magnetic disk device. In the magnetic disk device having the above mechanism, the magnetic disk has at least a magnetic film and a protective film formed on a non-magnetic magnetic disk substrate, and the surface thereof is coated with a liquid lubricant having a perfluoropolyether structure. The lubricating film has a structure represented by the chemical formula (1) or the chemical formula (2), and the lubricant supplied from the mechanism for supplying the lubricant into the magnetic disk device is represented by the chemical formula (3). A magnetic disk device having a structure and an average molecular weight of 2400 or less and 600 or more.