JPH02165401A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a good overwrite characteristic over the entire track of a medium by setting the recording gap length, recording electromotive force and medium coercive force of a magnetic head at specific relations. CONSTITUTION:The recording gap length GLW, recording electromotive force E and medium coercive force Hc of the magnetic head as well as the max. recording wavelength Lmin. of the innermost periphery and the max. recording wavelength Lmax. of the outermost periphery of the medium are set at the relations expressed by equation I. In equation I, Lmin denotes the max. recording wavelength of the innermost periphery of the medium; Lmax. denotes the max. recording wavelength of the outermost periphery of the medium; GLW denotes the recording gap length of the magnetic head; E denotes the recording electromotive force; Hc denotes the medium coercive force. The good overwrite characteristic over the entire track of the medium is obtd. in this way.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a magnetic recording and reproducing device, and in particular,
The present invention relates to a magnetic recording/reproducing device that can obtain good override characteristics.

(Prior Art) In digital magnetic recording, when rewriting a previously recorded signal, a so-called override method is generally adopted in which a new signal is directly overwritten using a recording head without using an erasing head.

The override method usually performs saturation recording in which the entire thickness of the magnetic layer is magnetized by a recording head.
The prerecorded signal is sufficiently attenuated, but as the recording linear density increases, the coercive force of the medium increases and the head gap narrows, making saturation recording difficult and making it difficult to ensure override characteristics. There is.

In other words, in order to improve the recording linear density (shorten the wavelength), the coercive force of the medium and the head gap are becoming narrower, and in general, the recording depth of the medium is about the same as or equal to the bed gap length. At most, it is about twice as long, but as the wavelength becomes shorter, there is a limit to how thin the medium layer can be, making it difficult to achieve saturation recording. By increasing the gap length of the head, the recording depth can be increased and the override characteristics can be improved.
Helad gap loss during reproduction causes a reduction in reproduction resolution.

Although the above problem can be solved by independently providing recording and reproducing heads with different gap lengths, this is not preferable because the structure becomes complicated and the cost increases.

Under these circumstances, various types of ferrite heads have been proposed in which a metal film is disposed on the gap mating surface of the ferrite head.

FIG. 7 is a sectional view of the main part of the MIG head.

This M I G (Metal In Gap) head is made of high saturation magnetic flux density material such as Sendust (for example, Bs
is approximately 10,000 [G] 11 placed on one or both sides of the gap mating surface, making it possible to create a higher recording magnetic field while taking advantage of the small eddy current of the ferrite material (Japanese Patent Application Laid-Open No. (Refer to Publication No. 61217901)
.

FIG. 8 is a sectional view of the main part of the DGL head.

This DGL (Dual Gap Length)
The head is made of a low saturation magnetic flux density material such as amorphous (for example, Bs of about 1000 [G] > 12) placed on one side of the gap mating surface. According to this head, during reproduction, the magnetic flux is the same as a normal head. However, during recording, the low saturation magnetic flux density material 12 causes magnetic saturation, so the effective gap length GLW is GL.
and the film thickness of the low saturation magnetic flux density material 12. In other words,
It will perform wide light and narrow read operations,
If saturation recording is possible, good override characteristics can be exhibited.

FIG. 9 is a sectional view of essential parts of the EDG head.

This EDG (Enhanced Dual Gap
Length) head is the MIG head and D
It combines the effects of both GL heads, with a low saturation magnetic flux density material 12 placed on the leading edge side of the head gap (upstream side in the magnetic recording medium transport direction) and a low saturation magnetic flux density material 12 on the opposing trailing edge side (downstream side in the magnetic recording medium transport direction). ) in which a high saturation magnetic flux density material 11 is arranged. According to this head, deeper recording is possible while maintaining resolution on a recording medium with high coercive force.

(Problems to be Solved by the Invention) The above-mentioned conventional technology has the following drawbacks.

A composite head such as the EDG head described above exhibits good override characteristics for a medium in which the coating thickness is relatively thin compared to the recording wavelength and is capable of saturation recording.

Incidentally, in recent years, there has been a demand for higher recording linear densities in magnetic recording and reproducing devices, and recording wavelengths are also becoming shorter.However, there is a limit to reducing the thickness of the magnetic material coating on the medium, so the coating thickness must be It becomes relatively thick compared to the recording wavelength. As a result, even if the composite head is used for such a medium, saturation recording is still difficult and good override characteristics cannot necessarily be obtained.

In view of this situation, the present invention attempts to optimize a high recording linear density magnetic recording and reproducing device by experimentally examining various combinations of medium constants, head constants, and recording conditions. be.

In other words, an object of the present invention is to provide a magnetic recording/reproducing device having good override characteristics.

(Means for solving the problem) The frequency ratio of the green signal and the override signal is set to 1:2.
and IF and 2F, respectively. When changing the recording density (wavelength) of the signal, the wavelength vs. override characteristic is
Peak at specific recording density (minimum override output value)
It is known that the wavelength at which the peak occurs depends on the recording gap length of the head.

However, if the gap length of the head is selected so as to produce a peak at a desired wavelength, the override characteristics can be made good, but the characteristics such as output and resolution are not necessarily good.

Furthermore, at high recording densities (short wavelengths), the head gap length must be set to 1/2 or less of the shortest wavelength used in order to improve the resolution of reproduction; , the peak of the wavelength vs. override characteristic is
Generally, this occurs on the high frequency side of the frequency range used, and the peak of the override recording density characteristic cannot be utilized.

In a composite head such as the EDG head mentioned above, the recording gap length can be arbitrarily selected independently of the reproduction gap length by changing the thickness of the low saturation magnetic flux density material placed on the leading edge side of the bed gap. can.

The inventor conducted an experiment on the relationship between the thickness of the low saturation magnetic flux density material, the recording magnetomotive force and medium coercive force of this composite head, and the peak of the override recording density characteristic, and the results are shown in Figures 1 to 3. We discovered the relationship shown in The recording medium used is a 3.5-inch disk-shaped magnetic recording medium.

Figure 1 shows the recording gap length GLW (reading gear length + thickness of the low saturation magnetic flux density material placed on the medium entry side (upstream side in the medium transport direction) of the magnetic pole near the operating gap) of the composite head and the override characteristics. A diagram showing the relationship between the wavelength of the IF multiplied signal of the IF multiplied signal MFM recording method that gives a peak,
Fig. 2 shows the relationship between the recording magnetomotive force E and the IF multiplied signal wavelength that gives the peak of the override characteristic, and Fig. 3 shows the relationship between the medium coercive force Hc and the IF multiplied signal wavelength that gives the peak of the override characteristic. FIG.

Here, the relationship shown in Figure 1 is based on the relationship between the film of low saturation magnetic flux density material placed on the medium entry side of the magnetic pole near the operating gap, when the read gap length of the head is fixed at 0.4 [μm]. The thickness was successively changed, and the experimental conditions at this time were such that the coercive force Hc of the recording medium was 1350 [Oe
], the recording current is the optimum recording current for 2F of each head.

The experimental conditions shown in Figure 2 are that the read gap length of the head is 0.4.
[μm], the film thickness of the low saturation magnetic flux density material is 0.7 [μm
mE, and the coercive force Hc of the recording medium is 1350 [Oe].

The experimental conditions shown in Figure 3 are that the read gap length of the head is 0.4.
[μm], and the film thickness of the low saturation magnetic flux density material is 0.7 [μm].
The recording current is the optimum recording current of 2F for each medium.

The recording gap length of the composite head, that is, the sum of the reproduction gap length and the thickness of the low saturation magnetic flux density material placed on the medium entry side of the magnetic pole near the operating gap, is GLw, and the IF multiplied signal wavelength that gives the peak of the override characteristic is Lp. Then, from FIG. 1, the relationship between GLW and Lp becomes as shown in equation 1.

Lp-aXGLd+b ... (1) Here, a and b are constants.

Assuming that the recording magnetomotive force is E, the relationship between E and Lp is as shown in the second equation from FIG.

Lp=cXE+d ... (2) Here, C and d are constants.

Further, assuming that the medium coercive force is Hc, the relationship between Hc and Lp is as shown in Equation 3 from FIG.

L p = (e / Hc) + f...
(3) Here, e and f are constants.

The above relationships also hold true under each interaction. As a result, the following fourth equation can be obtained from the first to third equations.

Lp=A (GLWxE/Hc)+B −(
4) Here, A and B are constants.

[
m], GLW: [m], E [Ar1, Hc
: [When expressed as A/ml, the following values were obtained for A and B.

A -15,4X 10 [1/m]
-(5) By the way, in a magnetic recording/reproducing device that uses a disk-shaped magnetic recording medium, the rotational speed of the disk is generally constant, and the recording frequency is constant regardless of the radius of the track. Therefore, between the inner circumference side and the outer circumference side of the disk,
Since the relative speeds between the recording medium and the head are different, the recording wavelength on the inner circumferential side is shorter than that on the outer circumferential side.

The maximum recording wavelengths at the innermost and outermost peripheries of the disc-shaped magnetic recording medium (recording wavelengths at the innermost and outermost peripheries when performing IF multiplied signal recording in the MFM recording method) are respectively La1n (2
, 9 rμml) and L IIax (5.08 [μm)]. Since the override characteristic produces a peak Lp at a specific recording wavelength, the relationship between the override value and L win and Lmax is as shown in Figures 4 to 6. There are three ways as shown in the figure.

Generally, if the override value is -30 [dB] or less, the override characteristics are considered to be good, so in FIG. This means that it has deteriorated.

In FIG. 5, good override characteristics are shown from the inner circumferential side to the outer circumferential side of the disc-shaped recording medium. Such characteristics can be said to be most suitable for magnetic recording and reproducing devices.

In FIG. 6, the override characteristic is good on the outer circumferential side of the disc-shaped recording medium, but it is deteriorated on the inner circumferential side.

The inventor conducted various experiments and confirmed that satisfying the following formula 6 is a condition for obtaining good override characteristics over all tracks.

From equations 4 to 6, if the following equation 7 is satisfied, good override characteristics can be obtained over all tracks.

0.75Lmln < 15.4 x 10' (GLWxE/Hc) <
1.25Lmax - (7) (Function) In this way, the recording gap length GLW of the magnetic head, the recording magnetomotive force E, the medium coercive force Hc, the maximum recording wavelength L gin at the innermost circumference of the medium, and the maximum recording at the outermost circumference Wavelength L
By setting 1aX to the relationship expressed by the seventh equation and configuring a magnetic recording/reproducing device, it becomes possible to obtain good override characteristics over all tracks of the medium.

0, 75L+in <Lp<1. 25LIlax
(6) (Example) The present invention will be described in detail below.

The inventors measured override values using the disk-shaped magnetic recording media, heads, and recording currents shown in the first to third examples. Note that the diameter of the disc-shaped magnetic recording medium is 3.5
inch, and its rotational speed is 300 rpm.

[First Example] Disc-shaped magnetic recording medium used Magnetic medium layer: Metal powder coating Coercive force Hc: 1350 [Oe] (107.4 [kA/ml) Head used (EDG head) Low saturation magnetic flux density material film thickness : 0.7 [μm] Reproducing gap length GL: 0.4 [μm] Recording gap length GLW: 1.1 [μm Number of turns per wire:
33X2 [T] Recording current: 70 rmA9-p E Recording magnetomotive force E22.31 [AT] Recording wavelength: outermost circumference of the medium IF"5.08 rpm
l (10,0 (kFRPI)) Innermost circumference of the medium IF-2,90 [μm1 (17,5 [kFRP!]) The override peak position and override value in this case were as follows.

Override peak position calculation value: AXGLWXE/He -3,64 [μm] Actual value 23.3 cm] Override value Media outermost knee 35 [dB] Media innermost knee 42 [dB] [Second example] Disk used Magnetic recording medium Magnetic medium layer: Coated with metal powder Coercive force Hc: 1550 [0el (123,4 [kA/ml) Head used (EDG head) Low saturation magnetic flux density material film thickness: 0.7 [μm] Reproduction gap length GL: 0.3 rμm] Recording gap length GLW: 1. O [μm Number of turns per wire:
33X2 [T] Recording current: 70 [mAp-p] Recording magnetomotive force E: 2.31 [AT] Recording wavelength: outermost circumference of the medium IF-3,63 [/jm] (1
4,0 [kFRPI]) Media innermost circumference IF-2,07 [μm] (24,5[kFRPI]) The override peak position and override value in this case were as follows.

Override value Medium outermost knee 33 [dB] Media innermost knee 41 [dB] C Third Example] Disc-shaped magnetic recording medium used Magnetic medium layer: Co-γ iron oxide coating Coercive force Hc: 1000 [0el ( 79,6 [kA/m] Head used (EDG head) Low saturation magnetic flux density material film thickness: 1.ICμm] Reproducing gap length GL: 0.4 [μm] Recording gap length GLW: 1°5 [μm Number of turns per :13
0X2 [T] Calculated value of override peak position: AXGLWXE/Hc -2,88Cμm] Actual value: 2.9 [μm] Recording current: 10 [mAp-p] Recording magnetomotive force E: 1.30 [AT recording wavelength: Media outermost circumference I F-5,08 rpm (10,0[kFR
PI]) Innermost circumference of medium IF-2,90 [μm] (17,5 [kFRPI]) The override peak position and override value in this case were as follows.

Override peak position calculation value: AXGLWXE/Hc -3,77 [μm] Actual value? 4.1 Cμm] Override value Medium outermost circumference knee 35 [dB] Media innermost circumference knee 45 [dB] Thus, in the first to third embodiments, the calculated value of the override peak position is almost the same as the actual measured value. We are doing so.

Moreover, since this override peak position Lp is between 0.75 times the recording wavelength L in at the innermost circumference of the medium and 1.25 times the recording wavelength L aX at the outermost circumference, The override value at the outermost circumference is -30 [d
B] or less, and it can be said that good override characteristics are obtained on all tracks of the medium.

Next, an example of a magnetic recording/reproducing device in which good override characteristics cannot be obtained on all tracks of the medium will be described for comparison with the above embodiment.

[Comparative example] Disc-shaped magnetic recording medium used Magnetic medium layer: Coated metal powder Coercive force Ha: 1550 coe] (123,4 (kA/ml) Head used (EDG head) Low saturation magnetic flux density material film thickness: O, , 4 [μm] Reproducing gap length GL: 0.3 rμm] Recording length + lubricant length GLV: 0.7 [μm Number of turns per wire: 33×2 [T] Recording current: 70 [mAp-p] Recording magnetomotive force E: 2. 31 [AT] Recording wavelength: outermost circumference of the medium IF-5,08 [μm1 (10
, 0 [kFRPI] ) Media innermost circumference IF - 2,90 [um] (17,5 [kFRP!] ) The override peak position and override value in this case were as follows.

Override peak position calculation value: AXGLWXE/Hc -2,02 [μm] Actual value: 1.6 [μm] Override value Media outermost knee 27 [dB] Media innermost knee 46 [dB] In this way, this example In this case, the override peak position Lp is 0.75 of the recording wavelength La1n at the innermost circumference of the medium.
and 1.25 times the recording wavelength L wax at the outermost circumference, so the override value at the outermost circumference of the medium exceeds -30 [dB]. Therefore, in this example, good override characteristics cannot be obtained on the outer peripheral side of the medium.

Now, in each of the above embodiments, the recording head is an ED.
The explanation has been made assuming that a G head is used.

In this EDG head, the medium entrance side of the magnetic pole near the operating gap is made of a magnetic material having a saturation magnetic flux density lower than that of the core of the magnetic head (for example, a magnetic material having a saturation magnetic flux density of 3500 Gauss or less), and the medium exit side is made of a magnetic material having a saturation magnetic flux density lower than that of the core of the magnetic head. It is sufficient if it is formed of a magnetic material having a saturation magnetic flux density higher than that of the core of the magnetic head (for example, a saturation magnetic flux density of 6000 Gauss or more).

In addition, it is not limited to only EDG heads,
It may be a DGL head, a MIG head, etc.
A magnetic material having a saturation magnetic flux density higher than the core of the magnetic head is disposed on the medium exit side of the magnetic pole near the operating gap, and a magnetic material having a saturation magnetic flux density lower than the core of the magnetic head is disposed on the magnetic material. On the magnetic head arranged,
It goes without saying that the present invention may also be applied.

Further, in the present invention, the recording wavelength of the disc-shaped magnetic recording medium may be of any size, but in particular, the maximum recording wavelength of the innermost circumference is 5 x 10' [m] or less. It can be applied to a linear recording density magnetic recording/reproducing device and is effective.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

That is, the recording gap length GLM of the magnetic head.

By configuring a magnetic recording/reproducing apparatus by setting the recording magnetomotive force E and the medium coercive force Hc in a predetermined relationship, it becomes possible to obtain good override characteristics over all tracks of the medium. In other words, various numerical settings of a high recording linear density magnetic recording/reproducing device (data settings of the recording gap length G Lv of the magnetic head, recording magnetomotive force E, and medium coercive force Hc) can be easily performed, and as a result, the relevant Design and manufacture of a magnetic recording/reproducing device becomes easier.

Furthermore, if a MIG head, DGL head, EDG head, etc. is used as the recording head, a magnetic recording/reproducing device with high recording linear density can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the recording gap length of a composite head and the IF multiplied signal wavelength that provides the peak of the override characteristic. FIG. 2 is a diagram showing the relationship between the recording magnetomotive force and the IF multiplied signal wavelength that gives the peak of the override characteristic. FIG. 3 is a diagram showing the relationship between the medium coercive force and the IF multiplied signal wavelength that gives the peak of the override characteristic. FIGS. 4 to 6 are diagrams showing the relationship between the override value and the maximum recording wavelength. FIG. 7 is a sectional view of the main part of the MIG head. FIG. 8 is a sectional view of the main part of the DGL head. FIG. 9 is a sectional view of essential parts of the EDG head. 11...High saturation magnetic flux density material, 12...Low saturation magnetic flux density material Fig. 1 Agent Patent attorney Michito Hiraki and 1 other person Fig. 2 ti4f<tcifl force E (AT) Fig. Eman u砿′J、5〔μ〕　　　　　　　　　　1　　1　　　　　　　　　　　　　　　　　　　　　　　　　1　;

Claims (4)

[Claims] (1) A disk-shaped magnetic recording medium consisting of a non-magnetic base layer and a magnetic medium layer laminated thereon, and a ring-shaped magnetic recording medium having a pair of magnetic poles arranged on the surface of the magnetic medium layer to form an operating gap. A magnetic recording and reproducing device comprising a head, wherein the coercive force of the magnetic medium layer, the recording gap length and the recording magnetomotive force of the magnetic head are equal to the maximum recording wavelength of the outermost circumference and the innermost circumference of the disk-shaped magnetic recording medium. A magnetic recording/reproducing device characterized in that the relationship between the maximum recording wavelength of and the following equation is satisfied. 0.75Lmin <15.4×10^4(GLW×E/Hc)<1.25
Lmax Here, Lmin: Maximum recording wavelength at the innermost circumference of the medium [m] Lmax:
Maximum recording wavelength at the outermost circumference of the medium [m] GLW: Recording gap length of the magnetic head [m] E: Recording magnetomotive force [AT] Hc: Medium coercive force [A/m] (2) The magnetic recording/reproducing device according to claim 1, wherein a magnetic material having a higher saturation magnetic flux density than the core is disposed on a surface facing the gap portion of the magnetic head. (3) The magnetic recording/reproducing device according to claim 1, wherein a magnetic material having a saturation magnetic flux density lower than that of the core is disposed on a surface facing the gap portion of the magnetic head. (4) A magnetic material having a saturation magnetic flux density higher than that of the core and a magnetic material having a saturation magnetic flux density lower than the core are disposed on the surface facing the gap portion of the magnetic head. The magnetic recording/reproducing device according to item 1.