JPH07326049A - Method for evaluating gliding characteristic of magnetic recording medium - Google Patents

Abstract

PURPOSE:To exactly detect abnormal projections etc., on a medium which hinder floating of a head slider and to determine an exact gliding height by using a technique of monitoring the contingent contact between the head slider and the medium. CONSTITUTION:An elastic wave detecting element 8 detects the contact of the head slider 2 and a magnetic disk 1. Namely, the elastic waves generated on the slider side by contact of both are propagated via a suspension 5 and a mounting member 5a to a head mount 6. The piezoelectric effect corresponding to such elastic waves is generated in the element 8. The voltage signal outputted from the element 8 is passed through an amplifier 9 and an A/D converter 10 and the voltage V(j) meeting a sampling interval DELTAt is taken into a computer 11. The computer 11 calculates the value Vmax determined by obtaining the square root of the square sum of the voltage V(i) (i=1 to N, i<j) successively from the largest of positive V(i) per 1 rotation of the disk at the respective relative speeds and determines the floating height h0 at the air outflow end of the slider at the relative speed at which Vmax. begins to rise in the slider floating curve indicating a relation between Vmax and the respective relative speeds as the gliding height.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating glide characteristics of a magnetic recording medium in which information is recorded or reproduced by a floating magnetic head.

[0002]

2. Description of the Related Art In a magnetic recording device, such as a hard disk device, which mainly comprises a floating magnetic head and a magnetic recording medium, a magnetic recording medium is rotated at a high speed of several thousands rpm to generate an air flow on the medium. The magnetic field is generated and the air flow is used to levitate the head slider mounted on the magnetic head to maintain the gap between the medium and the medium to about submicron, and then the information is recorded and reproduced.

In order to perform stable recording / reproduction of information based on the above-described operation principle, it is essential that the flying stability of the head slider flying above the medium is good. Since the gap between the head slider and the medium is extremely small, around submicron, the surface shape of the slider and the medium, and the presence of foreign matter (dust, abnormal protrusions, etc.) have a significant adverse effect on the flying characteristics of the slider. It becomes a factor to exert. In order to ensure that the flying height (hereinafter referred to as the glide height) that allows the head slider to fly stably is checked by checking whether or not factors that hinder the flying of this head slider are present on the medium. An inspection called a glide test has been performed after the medium is manufactured.

Here, the glide evaluation methods (evaluation means and two types of glide characteristic evaluation methods) that have been conventionally performed will be briefly summarized.

First, the flying stability of the head slider on the actual medium is generally evaluated by monitoring the contact state between the head slider and the medium. Such an evaluation means has been proposed as a conventional technique. That is, an elastic wave is generated in the head slider due to the impact force when the flying slider such as a protrusion existing on the medium comes into contact with the head slider, and the elastic wave is detected by the elastic wave detection element (piezo sensor, AE sensor). ), And the state of contact between the two is determined by the magnitude of the signal output from the elastic wave detecting element. In principle, the two types of elastic wave detecting elements described above are the same dielectric (for example, zirconate titanate).
The sensor that is directly attached to the head slider is called a piezo sensor, and the sensor mounted on the head mount that holds the suspension to which the head slider is attached is called an AE sensor. Are differentiated.

Next, regarding a glide characteristic evaluation method (glide height assurance method), the following method has been proposed as a conventional technique.

Glide height guarantee by the reference disk As described above, the signal strength output from the elastic wave detecting element depends on the contact state between the head slider and the medium, and it depends on the degree of contact or the size of the contacting protrusion. Change. Therefore, in order to guarantee the glide height of the medium on the basis of the magnitude of the output signal, a criterion for judging whether or not the glide height to be guaranteed in advance can be realized on the medium to be inspected ( It is necessary to know the threshold). That is, in this method, a reference disk having a protrusion whose height is equal to the glide height to be guaranteed is used, and the head slider is levitated on the disc at the same flying height as the protrusion height. Measuring the output voltage from the elastic wave detecting element when passing over, the voltage value as a threshold value, if the output voltage observed on the actual medium is below the threshold value,
It is judged to pass. The above-mentioned reference disc is defined in its shape and height, and a disc having protrusions having a rectangular parallelepiped shape having a certain length in the disc radial direction is usually used for the calibration. .

Glide height guarantee by head slider levitation characteristic curve This method is described in, for example, the Journal of Japan Applied Magnetics Vol. Supplement,
As described in No.S2,1993, P292, the relative parameter between the head slider and the medium to be inspected is changed, and the statistical parameter calculated from the voltage value output from the elastic wave detecting element under each relative velocity. (For example, the arithmetic mean value or standard deviation value of the voltage waveform per one rotation of the medium, the details of which will be described later), and a head slider flying characteristic curve which is a curve showing the relationship between the relative speed and the statistical parameter in this case is calculated. The relative speed at which the statistical parameter value starts rising (that is, the relative speed at which the head slider starts contacting the medium) is determined from this curve, and the glide height is estimated from the flying height of the head slider at that relative speed. To do.

This method does not require the calibration with the reference disk as required in (3) and can estimate the glide height relatively easily as compared with the former method.

[0010]

By the way, in recent years, along with the increase in capacity of software and processed data due to the spread of multimedia and the like, a computer having a higher processing function is required, and an external storage device thereof is required. Similarly to the former, the magnetic recording device is required to have improved functions such as high capacity and high speed access. As represented by a hard disk device, in a magnetic recording device using a floating magnetic head, it is possible to reduce the flying height of the magnetic head slider from the medium and improve the recording density per unit area on the medium. , Which will be a breakthrough in achieving higher capacity.

Based on the technical background as described above, it is necessary to reduce the glide height in the actual medium in order to realize a low flying height of the head slider, and accordingly, the glide height is more accurate. Although there is an urgent need to establish a method for evaluating the above, there are the following problems in the glide evaluation methods according to the related art.

Problems of Glide Height Guarantee by the Reference Disc In the conventional reference disc, the reference protrusion formed on the disc substrate has a rectangular parallelepiped shape (disc radial direction) by a dry process (sputtering etc.) or a wet process (chemical etching etc.). It has a certain length). However, in these reference protrusion manufacturing processes, it is difficult to make the height of the formed reference protrusion from the disk substrate surface constant in the radial direction, and the reference protrusion height becomes low (that is, low glide evaluation). (For correspondence), the degree of variation with respect to the reference height becomes more remarkable, and it becomes insufficient as a reference disk for calibration.

It should be further taken into consideration that there is a fundamental problem with this method that calibration with a reference disk is adequate to determine the actual head slider / real medium contact condition. Is. Usually, the shape of the abnormal protrusions that are presumed to be formed in the dust observed on the medium and the medium manufacturing process (texturing, film formation of a magnetic thin film, etc.) is similar to the above-mentioned reference protrusion. It has not a continuous rectangular parallelepiped shape, but rather a discontinuous shape element close to a point. Therefore, even if the threshold value of the output signal from the elastic wave detection element determined by the reference disk is used for the actual glide characteristic evaluation, it cannot be said that the true contact state between the two is determined. .
Therefore, this method is only a means used to uniquely determine the glide height, and in consideration of the above-mentioned problems, some uncertainties are present.

Problem of Glide Height Guarantee by Head Slider Floating Characteristic Curve In this method, the relative speed between the head slider and the medium is changed to obtain a disk 1 obtained at each relative speed.
From the output voltage waveform from the elastic wave detecting element corresponding to the rotation, statistical parameters (arithmetic mean value (Vav
e.), or standard deviation value (Vrms), see Fig. 1 and equations (1) and (2)), and determine the glide height by monitoring the rate of change of its absolute value with respect to relative velocity. To do.

[0015] As shown in equations (1) and (2), both parameters provide information on the average output of the output waveform within a certain reference time (here, the time corresponding to one rotation of the disk). . Therefore, for example, in a certain waveform, the information is averaged based on the average output voltage, and it is difficult for the absolute value to have a relatively clear significance. Therefore, as shown in Fig. 2, the slider flying speed (TDV: To
The glide height determined by uch Down Velocity) is
This output waveform becomes large as a whole. That is, it can be said that it indicates the flying height when the head slider starts contacting the medium with a relatively high frequency between the head slider and the medium.

However, the contact frequency between the head slider and the medium, which is the criterion for the pass / fail judgment in the normal glide test, is the case where there are several levels of waveforms that exceed a preset threshold value, and the number of contact is more than that. At the level of, it will be judged as a disc that is practically endless. Therefore, in the glide test, it is necessary to target sudden signals that exceed the average output rather than the above average information, and average information such as Vave. And Vrms near TDV. Even if the glide height is estimated from the above, it is difficult to say that the glide characteristics are accurately evaluated, considering the definition of the parameter serving as the criterion.

The present invention has been made under the above-mentioned background, and more accurately evaluates the flying stability (glide characteristics) of a head slider having a flying height lower than that of the prior art. The purpose is to provide a characteristic evaluation method.

[0018]

In order to solve the above problems, the method for evaluating the glide characteristics of a magnetic recording medium according to the present invention is (Structure 1): The flying head slider can fly stably on the magnetic recording medium. A method for evaluating the glide characteristics of a magnetic recording medium for determining the glide height, which is the flying height, using an elastic wave detecting element that detects contact between the magnetic recording medium and the flying head slider and converts the contact voltage into a voltage. When the relative speed between the magnetic recording medium and the head slider is changed, the elastic wave detection is performed while the head slider makes one round on a predetermined disk radius of the magnetic recording medium under each relative speed. The output voltage curve shows the change in voltage output from the device over time, and the output voltage value at the top of each peak or valley that appears in this output voltage curve is cut off. Let V (i) be the logarithmic value or the absolute value of the difference between the output voltage values at the tops of the adjacent peaks and valleys, and select the largest V (i) from the largest to the nth. When i of V (i) is i = 1 to n, the relationship between each relative speed and the value Vmax obtained by taking the square root of the sum of squares of V (i) at i = 1 to n is shown. The curve is a head slider flying curve, and in the head slider flying curve, Vmax with respect to the relative speed thereof
The flying height of the head slider at the relative speed at which the value starts to rise is defined as the glide height. As an aspect of this configuration 1, (configuration 2) a method for evaluating glide characteristics of a magnetic recording medium of configuration 1 In the above configuration, the flying height of the head slider is the flying height h0 at the air outflow end of the air bearing surface of the head slider.

[0019]

According to the above-mentioned structure, since the amplitude value in the output voltage curve for one round of the disk is monitored for each relative speed, the sensitivity is higher than that in the case of evaluation using the conventional statistical parameters. It is possible to detect the contact state between the head slider and the medium, and to determine the glide height more accurately. Then, the number of output voltage values V (i) monitored on the output voltage curve is set such that i is 1 to n depending on the allowable contact frequency preset in the magnetic recording medium to be inspected.
By setting up to, more accurate glide characteristics can be evaluated.

Further, the magnetic head slider flying above the medium often has a lower flying height (h0) at the outflow end than the flying height (h1) at the air inflow end on the air bearing surface. Since the edge has a higher probability of coming into contact with the medium, the glide height becomes more accurate by using the latter flying height h0 as a reference.

[0021]

EXAMPLES First, an apparatus for carrying out the method of this example will be described, and then the method of this example will be described.

3 to 5 are explanatory views of an apparatus for carrying out the method of this embodiment.

In FIGS. 3 to 5, reference numeral 1 is a magnetic disk which is a magnetic recording medium.
Is held by a clamp 4b on a disk rotation spindle 4a of a rotation device 4, and is rotated by driving a motor 4c having the disk rotation spindle 4a as a rotation axis.

A head slider 2 is arranged on the magnetic disk 1. The head slider 2 is fixed to the front end of the suspension 5, and is fixed to the front end of the head mount 6 via a mounting member 5a mounted to the base end of the suspension 5. The head mount 6 is attached to a head slider moving mechanism 7 whose position can be adjusted in the horizontal and vertical directions.

Further, an elastic wave detecting element (AE sensor) 8 is attached to the head mount 6, and the output of this elastic wave detecting element 8 is used for data processing through an amplifier 9 and an A / D converter 10. Is sent to the personal computer 11.

In the above structure, the head slider 2
Is in contact with the surface of the magnetic disk 1 with an appropriate pressing force (head load) by the elastic force of the suspension 5 when the spindle 4a is stopped.
The contact slide running on the magnetic disk 1 is continued until the rotation speed of the magnetic disk 1 reaches a predetermined rotation speed, and when the predetermined rotation speed is reached, the head slider 2 and the magnetic disk 1
When the spindle 4a is stopped by the action of the air flow generated between
When the rotation speed of a is started to decrease and reaches a predetermined rotation speed, the floating traveling state is changed to the contact sliding traveling state and stopped.

The elastic wave detecting element 8 is the head slider 2
And the magnetic disk 1 are detected. That is, the elastic wave generated on the head slider side due to the contact between the two propagates to the head mount 6 via the suspension 5 and the mounting member 5a. Along with this, a piezoelectric effect corresponding to the elastic wave is induced in the elastic wave detecting element 8, and the contact state can be monitored by measuring the voltage signal generated thereby.

In this embodiment, the flying height of the head slider 2 and the rotational speed of the magnetic disk 1 are changed (that is, the relative speed of the head slider / medium is changed).
It is necessary to grasp Vmax from the output voltage curve (see FIG. 6) per rotation of the magnetic disk at the relative speed at each flying height. for that reason,
The output voltage signal (analog signal) sent from the elastic wave detection element 8 is amplified by the amplifier 9, and then the A / D converter 10
The system adopts a system in which the voltage V (j) (j = 1 to N ′) corresponding to the sampling interval Δt is taken into the personal computer 11 by digitalization. Where N
′ Corresponds to the number of output voltages V (j) for one round of the disk at each relative speed (υ) and is represented by the following equation.

N ′ = (πr / 30υ) / Δt (3) Where, ν: Relative speed between head slider / medium (m / s) r: Disk radial position (m) where head slider is installed Δ t: Sampling time (sec) Then, the voltage V (i) for which Vmax is to be calculated must be grasped from the output voltage waveform. The procedure is as follows. With respect to the output voltage curve per one rotation of the magnetic disk at the speed, as shown in FIG. 7, V (j) on the + side of 0 V in the output voltage curve is selected, and the V (j) is selected from the maximum value. In turn, set it to V (i) (i =
1 to N, i <j), and then the voltages V (1) and V corresponding to the number n (n <N) of peaks to be targeted.
(2), V (3), ... V (n) (n <N) is calculated by taking the square root of the sum of squares Vmax.

Vmax = {V (1) ² + V (2) ² + ... V (n) ² } ^0.5 (4) The system and the evaluation parameter (Vma) as described above.
x) is used to set the magnetic disk 1 and the head slider 2 in the apparatus shown in FIGS. Next, the spindle 4a is rotated to a predetermined rotation speed so that the head slider 2 floats on the magnetic disk. Then, the rotation speed of the spindle 4a is decreased from that state, and Vmax in the output voltage curve per one rotation of the magnetic disk under each rotation speed is decreased.
Check for changes (eg, i = 1). Then, the head slider flying curve as shown by the solid line in FIG. 8 is obtained. In FIG. 8, the flying height h0 (see FIG. 9) of the air outflow end on the air bearing surface of the head slider 2 at the relative speed at which Vmax starts to rise is defined as the glide height.

Next, the results of evaluating the glide height h0 of magnetic disks having different head slider flying stability (glide characteristics) by the above method will be described.

First, a magnetic disk used for measurement was manufactured as follows.

That is, as shown in FIG. 10, the diameter is 65 m.
After the NIP plating layer 13 is formed on the aluminum alloy substrate 12 having a thickness of 20 m by electroless plating at a heat of 20 μm, the concentric mechanical texture 1 is formed by lapping tape.
4 was applied to the NIP layer 13. At that time, a SiC abrasive grain type (GC # 3000, average abrasive grain size: 5 μm) wrapping tape was used, the rotation speed of the disk sample attached to the texturing device was 200 rpm, the tape feed speed was 50 cm / min, and the tape pressure was set. 1.0 kgf /
It was set to cm ² and textured. The surface roughness produced by this texturing is 30 nm in Rp (height between the highest protrusions from the average line of the roughness curve).
Met. Then, 100 n of Cr is used as the underlayer 15 on the NIP layer on which the mechanical texture 14 is applied.
m, CoNiC as the magnetic layer 16 on the underlayer 15
r was deposited in a thickness of 50 nm, and carbon was deposited in a thickness of 20 nm as a protective layer 17 on the magnetic layer 16 by sputtering. At the time of sputtering each of these layers, argon gas with a purity of 99.9% was used as the atmosphere gas, and the gas pressure was 5 mT.
orr (gas flow rate, Ar: 10 SCCM), input power:
The film is formed under the conditions of 100 W, back pressure: 10 ⁻⁷ Torr, and no substrate heating. Further, on the protective layer 17, the lubricating layer 1
8 is formed, but this is PFPE (Fo
mblin AM2001) and HC in its solvent
Each of FC (AK-225 manufactured by Asahi Glass Co., Ltd.) was used to form a magnetic recording medium by applying a film having an average film thickness of 2 nm by a dipping method. The surface roughness (Rp) of the magnetic recording medium on which the lubrication layer was formed was the same as the surface roughness of the surface irregularities produced by texturing.

Further, the Rp of the texture in FIG.
A disk manufactured in the same manner as the magnetic recording medium except that the thickness was set to 25 nm was used as the magnetic recording medium.

Further, the Rp of the texture in FIG.
A disk manufactured in the same manner as the magnetic recording medium except that the thickness was set to 20 nm was used as the magnetic recording medium.

Further, the Rp of the texture in FIG.
A disk produced in the same manner as the magnetic recording medium except that the thickness was set to 15 nm was used as the magnetic recording medium.

Further, the Rp of the texture in FIG.
A disk manufactured in the same manner as the magnetic recording medium except that the thickness was set to 10 nm was used as the magnetic recording medium.

As described above, the glide characteristics of magnetic recording media manufactured by changing the surface roughness are evaluated, and the head slider flying curve (Vmax-relative velocity relationship, j = 1) of each magnetic recording medium is evaluated. 11)
Shown in. For comparison, FIG. 12 also shows the results obtained by examining Vrms (calculated from the equation (2)) and the relative velocity (υ).

FIG. 13 shows the relationship between the glide height h0 calculated from the head slider flying curve and the surface roughness (Rp) of the magnetic recording medium.

In this glide test, the medium was 1.5 kgf.
With the tightening torque of cm, the head slider 2 is held after being held by the disk rotation spindle 4a equipped in the glide characteristic evaluation apparatus shown in FIGS.
Air bearing surface (ABS surface) on the inner side with respect to the medium 1
The head slider 2 is set on the medium so that the center of the head is 17.5 mm from the center of the medium, and the disk rotation spindle 4a is rotated up to 4000 rpm so that the head slider 2 floats and runs on the magnetic disk 1. From that state, the rotation speed of the spindle 4a is decreased, and Vmax and Vrms in the output voltage curve per one rotation of the magnetic disk under each rotation speed are examined for each magnetic recording medium.

The head used in this measurement is IBM3
370 type in-line head, head load 6.5gf, head slider material Al ₂ O ₃ -T
iC, and the flying height h0 of the air outflow end on the air bearing surface of the head slider are shown in FIG.
The one with the characteristics shown in is used.

Further, this measurement is carried out in a clean room with a clean cleanliness of 100, in which the room temperature is 24 ° C. and the humidity is 40% RH. It was H.

As a result, as shown in FIGS. 11 and 12, when the flying characteristics of the head slider from the magnetic recording medium to Vrms were examined, the relative velocity (υ ') at which the Vrms value started to rise was too large. Although no difference is observed, a clear significant difference is observed in ν ′ for each medium in Vmax in this example as compared with the former.

From the above results, FIG. 13 finds the flying height corresponding to υ ′ of each medium from FIG. 14 and finds the glide height h.
And the surface roughness (Rp) of the magnetic recording medium to
However, the evaluation by Vmax more accurately captures the difference in glide height, which is considered to change due to the difference in surface roughness, than the evaluation by Vrms, and the effect of this example is verified. Has been done.

Considering that the distance from the center line of the roughness curve of each medium to the air outflow end of the air bearing surface of the head slider corresponds to the flying height h0, the relative velocity between the head slider and the medium is reduced. When the flying height is reduced by the above, it is presumed that the head slider first comes into contact with the highest convex portion on the medium defined by the surface roughness parameter Rp. However, in the evaluation by Vrms, even if the head slider first comes into contact with the convex portion, the detection signal occupies the output voltage waveform (corresponding to the output voltage for one rotation of the disk here) for which Vrms is calculated. Since the ratio is very small, it is conceivable that no clear difference appears in the absolute value as a result. On the other hand, Vma according to the present embodiment
While x is the average information of the output voltage waveform corresponding to one rotation of the disk in the former, it is an evaluation parameter for the sudden signal as described above, so that there is a problem with the glide characteristics. It has been shown to be more suitable for detecting such abnormal protrusions having a low existence probability on the entire medium surface.

In the above embodiment, in the output voltage waveform for one rotation of the disk, the peak voltage value (V
Although Vmax is calculated only from the largest voltage value (in the case of j = 1) of (j)), j is set to 1 depending on the allowable contact frequency preset in the magnetic recording medium to be inspected.
By setting up to n, more accurate glide characteristics can be evaluated.

Further, in the above embodiment, Vmax is determined by performing peak detection for V (j) on the + side of 0 V in the output voltage curve, but the present invention is not limited to this, and Vmax is determined in the output voltage curve. V that is more negative than 0V
Peak detection may be performed from the negative output voltage curve for (j), and Vmax may be determined based on the above equation (4). Furthermore, in the output voltage curve, the PV value (Pe
ak to Valley), and from the largest one to V
As (1), V (2), ..., V (n), Vmax may be determined by taking the square root of the sum of squares thereof.

In the above-described embodiment, the relative velocity (υ ') at which the Vmax value starts to rise from the head slider flying curve.
The glide height is determined by referring to the levitation characteristics of the head sliders used for inspection, and in order to calculate υ ′ more accurately according to the head slider levitation curve, for example, a moving average It goes without saying that a method such as a method or a frequency domain method may be used.

In the present embodiment, the head slider / medium contact detecting means (elastic wave detecting element) A
Although the E sensor is used, the application of, for example, a piezo sensor for directly mounting the element on the head slider is not excluded.

[0050]

As described in detail above, the glide characteristic evaluation method according to the present invention, in short, is basically the evaluation of the contact state between the head slider and the medium using statistical parameters, and the glide height is evaluated from the average information. In contrast to the conventional technology that has determined the depth, a method of monitoring sudden contact between the two is used, so abnormal protrusions on the medium that hinder the flying of the head slider can be detected more accurately than before,
A more accurate glide height can be determined.

[Brief description of drawings]

FIG. 1 is a diagram showing an output voltage waveform from an elastic wave detecting element corresponding to one rotation of a disk.

FIG. 2 is a diagram showing a head slider flying curve (relationship between output voltage and relative speed between head slider / medium).

FIG. 3 is an explanatory diagram of a glide characteristic evaluation device.

FIG. 4 is an explanatory diagram of a glide characteristic evaluation device.

FIG. 5 is an explanatory diagram of a glide characteristic evaluation device.

FIG. 6 is a diagram showing an output voltage waveform from an elastic wave detecting element corresponding to one rotation of the disk.

FIG. 7 is a diagram showing a voltage waveform in which V (j) on the + side of 0 V is selected from the output voltage waveform from the elastic wave detection element corresponding to one rotation of the disk.

FIG. 8 is a diagram showing a head slider flying curve.

FIG. 9 is a diagram illustrating the flying height of a head slider.

FIG. 10 is a partial cross-sectional view of a magnetic recording medium in an example of the present invention.

FIG. 11 is a diagram showing a head slider flying curve of each magnetic recording medium based on evaluation of Vmax.

FIG. 12 is a diagram showing a head slider flying curve of each magnetic recording medium evaluated by Vrms.

FIG. 13: Glide height and surface roughness of magnetic recording medium (R
It is a figure which shows the relationship of p).

FIG. 14 is a diagram showing the relationship between the flying height at the air outflow end of the air bearing surface of the head slider and the relative speed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 2 ... Head slider, 4 ... Rotation device, 4a ... Disk rotation spindle, 4b ... Clamp, 4c ... Motor, 5 ... Suspension, 5a ... Mounting member, 6 ... Head mount, 6a ... Mounting base, 7 …
Head slider moving mechanism, 8 ... Elastic wave detecting element, 9 ...
Amplifier, 10 ... A / D converter, 11 ... Personal computer, 12 ... Aluminum alloy substrate, 13 ... NiP plating layer, 14 ... Mechanical texture, 15 ... Underlayer (Cr), 16 ... Magnetic layer (CoNiCr), 17 ... Protective layer (carbon), 18 ... Lubrication layer.

Claims (2)

[Claims] 1. A method for evaluating a glide characteristic of a magnetic recording medium for determining a glide height, which is a flying height at which a flying head slider can fly stably on a magnetic recording medium. When an elastic wave detecting element that detects contact with a die head slider and converts it into a voltage is used, and when the relative speed of the magnetic recording medium and the head slider is changed, the head slider is An output voltage curve is a curve showing a temporal change in the voltage output from the elastic wave detecting element while the magnetic recording medium makes one round on a predetermined disk radius. Let V (i) be the absolute value of the output voltage value at the top of the valley or the difference between the output voltage values at the tops of the adjacent peaks and valleys.
When the values of V (i) from the maximum value to the nth value are sequentially set as i of V (i) i = 1 to n, V (i) at i = 1 to n A curve showing the relationship between the value Vmax obtained by taking the square root of the sum of squares of V and each relative speed is a head slider levitation curve, and in the head slider levitation curve, in the relative speed at which the Vmax value with respect to the relative speed begins to rise,
A method for evaluating the glide characteristics of a magnetic recording medium, characterized in that the flying height of the head slider is set as the glide height. 2. The method for evaluating glide characteristics of a magnetic recording medium according to claim 1, wherein the flying height of the head slider is the flying height h0 at the air outflow end of the air bearing surface of the head slider.
A method for evaluating glide characteristics of a magnetic recording medium, characterized by: