JPH1116123A - Thin film magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the intensity of a magnetic field in a track part enough to record to a magnetic recording medium and to enable the high density magnetic recording by specifying the length of a magnetic gap in an extending part and the length of a magnetic gap in the track part. SOLUTION: When the length of a narrow magnetic gap is denoted as L1a and the length of a wide magnetic gap as L1b, magnetic field intensities of these magnetic gaps are expressed by H1a=K/L1a and H1b=K/L1b respectively, where K is a constant determined by the whole shape of a head, a coil current and a magnetic characteristic of a magnetic core material. When this constant is >= two times of coersive force of the magnetic field intensity of H1a and is <= one half of coersive force of the magnetic field intensity of H1b, the magnetic intensity of the narrow magnetic gap 4 in the track part becomes strong enough to record to a magnetic recording medium. Moreover, when the length of L1b is >= four times of the length of L1a, the magnetic field intensity of the wide magnetic gap 3 becomes weak enough not to write to the magnetic recording medium by mistaken and high density recording becomes possible without blurring with writing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic disk drive,
The present invention relates to a magnetic head used for a device that records or reads information on a magnetic recording medium such as a magnetic tape device, and particularly to a thin film magnetic head suitable for high-density recording.

[0002]

2. Description of the Related Art FIG. 2 shows a cross section of a magnetic core of a conventional magnetic head viewed from a lateral direction. Upper magnetic core 5,
It is composed of a lower magnetic core 7 and a current coil 6, and a magnetomotive force is generated by a current flowing through the current coil 6, and a magnetic flux is generated inside the magnetic cores 6 and 7.

In the magnetic gap 8, which is a minute gap of 1 μm or less, a magnetic flux leaks slightly to the outside, and the leaked magnetic flux is used for recording data on a magnetic recording medium. That is, a high-speed rotating disk (magnetic disk) coated with a thin magnetic material
The magnetic head is held at a very small height using air pressure on the magnetic head, and the current flowing through the current coil 6 is controlled based on the data to be recorded. The change is recorded on the magnetic flux disk.

Conversely, a magnetic flux from a magnetic disk is taken in from a magnetic gap, and a voltage generated in a current coil is detected by an electromagnetic induction effect due to a time change of the magnetic flux, and is used for reading data recorded on the magnetic disk. You can also.

FIG. 3 shows the shape of a magnetic core of a conventional magnetic head viewed from the direction of the tip of the magnetic gap (from the air bearing surface side). The interval (L3) of the gap 10 between the upper magnetic core 9 and the lower magnetic core 11 is called a magnetic gap length. The magnetic field strength due to the magnetic flux leaking from the magnetic gap increases as the gap length L3 decreases.

[0006] Also, as the width (track width) of the upper magnetic core 9 becomes smaller, the width of the leakage magnetic flux becomes narrower and the recording density can be increased. However, if it is too narrow, the magnetic field intensity becomes weaker and recording on the magnetic disk becomes impossible. Therefore, the minimum track width that can be used has been limited to about 2 μm conventionally.

In order to reduce the minimum track width, the upper magnetic core 12 shown in FIG.
A structure has been devised in which an overhang portion 13 is provided. In this structure, since the wide magnetic core is located above the narrow track width, the magnetic resistance of the upper magnetic core is reduced. As a result, the magnetic flux in the magnetic core increases and the leakage flux from the magnetic gap also increases, so that the magnetic field intensity also increases, and a magnetic field intensity that enables magnetic recording even with a finer track width is obtained, and the magnetic recording density can be improved. there is a possibility.

[0008]

However, if the gap length L3 of the gap 15 at the overhang portion 13 is not set to an appropriate length, the magnetic field intensity becomes too strong, and not only the original recording track portion, but also the There is also a problem of writing bleeding in which data is erroneously recorded on both sides, and its prevention is an important issue.

In view of the above problems, an object of the present invention is to provide a thin-film magnetic recording head having a fine track width which does not cause writing blur and can improve the magnetic recording density.

[0010]

FIG. 5 shows a magnetization curve (B) showing a change in magnetic flux density B of a magnetic recording medium with respect to an applied magnetic field H.
(H curve) is shown.

When the magnetic field H is increased from the point at which the magnetic field strength at the initial value (point a) is zero, the magnetic flux density B gradually increases and begins to saturate at the point b. When the magnetic field is further increased to the point c, the magnetic flux is sufficiently saturated.
Called s.

Next, when the magnetic field is reduced, the route from point b does not follow the previous route, and the magnetic flux density B hardly decreases to point d.

When the magnetic field strength is further reduced in the negative direction, the magnetic flux density starts to decrease rapidly and becomes zero at the magnetic field strength -Hc. The magnetic field strength Hc is a value called a coercive force, and is one of parameters indicating recording characteristics of the magnetic medium.

When the magnetic field is further reduced, the magnetic flux density becomes a negative value, begins to saturate at point e, and saturates sufficiently at point f. Next, when the magnetic field strength is changed to a positive value again, the magnetic flux density starts to increase from the point g. Further, the magnetic flux density becomes zero again at the magnetic field strength Hc, and the same route is followed from the point b.

By applying a magnetic field sufficiently larger than the coercive force Hc to the magnetic recording medium and reversing the sign, the sign of the magnetic flux density of the magnetic recording medium, in other words, the direction of the magnetic flux can be reversed. . Thereafter, even if the applied magnetic field intensity becomes zero, the value of the magnetic flux density and its sign can be retained, so that data recording becomes possible.

On the other hand, if the applied magnetic field strength is sufficiently smaller than the coercive force Hc, no new data is recorded.

Therefore, in order to solve the above-mentioned problem of preventing the bleeding, the gap 16 of the original track portion of the recording head and the gap 15 of the overhang portion of the upper core are required.
The magnetic field strength is adjusted by optimizing the length of each of them, so that the original magnetic field strength of the gap 16 of the trap portion is sufficient for recording on the magnetic recording medium, and the overhang portion 13 is formed. The magnetic field strength of the gap 15 may be set sufficiently low to prevent erroneous writing on the magnetic recording medium.

[0018]

FIG. 6 is a perspective view of a thin-film magnetic head according to one embodiment of the present invention. Upper magnetic core 1
7, a lower magnetic core 20, and a current coil 21. A narrow gap 18 at the track portion and a wide gap 19 at the overhang portion are formed. FIG. 1 shows the shape of the magnetic core of the thin-film magnetic head as viewed from the tip of the magnetic gap. Assuming that the length of the narrow magnetic gap is L1a and the length of the wide magnetic gap is L1b, the respective gap magnetic field strengths H1a and H1b are expressed by the following equations.

[0019]

H1a = K / L1a (1) H1b = K / L1b (2) where K is a constant determined by the overall shape of the head, the coil current, and the magnetic characteristics of the magnetic core material. From the description of the BH curve of the magnetic recording medium, the magnetic field strength of H1a is twice or more the coercive force Hc (formula (3)), and the magnetic field strength of H1b is 以下 or less of the coercive force Hc (formula (4)). ), The magnetic field strength of the gap 4 in the track portion becomes strong enough for recording on the magnetic recording medium, and the magnetic field strength of the gap 3 in the overhanging portion is sufficiently weak to be erroneously written on the magnetic recording medium. Since there is no recording, high-density recording without writing blur is possible. Further, the expression (5) holds from the expressions (3) and (4).

[0020]

H1a ≧ 2Hc (3) H1b ≦ Hc / 2 (4) H1a / H1b ≧ 4 (5) Further, the expression (6) is established from the expressions (1), (2) and (5). .

[0021]

L1b / L1a ≧ 4 (6) It can be seen from the above equation that the length of L1b should be at least four times L1a. The constant K and the gap length L1a in the equations (1) and (2) are set so that a sufficient head magnetic field can be obtained in consideration of the coercive force Hc of the magnetic recording medium.
The coil current and the magnetic characteristics of the magnetic core material are selectively adjusted and optimized. In this embodiment, since magnetic recording without writing blur can be performed even with a fine track width, there is an effect that high-density recording can be realized.

FIG. 7 shows another embodiment of the present invention. As in the perspective view of the thin-film magnetic head of FIG.
It comprises a lower magnetic core 25 and a current coil 26. In this embodiment, a step is also formed in the lower magnetic core 25. FIG. 8 shows the shape of the magnetic core as viewed from the tip of the magnetic gap. The length of the narrow magnetic gap 29 is L8
a, when the length of the wider magnetic gap 30 is L8b, the equation (7) is established similarly to the equation (6).

As in the above embodiment, the magnetic field intensity of the track portion is sufficient for recording on the magnetic recording medium, and the magnetic field intensity of the wider magnetic gap on both sides thereof is sufficiently weak. Disappears and high-density recording becomes possible.

[0024]

L8b / L8a ≧ 4 (7) In this embodiment, since the lower magnetic core is formed with a step having a convex central portion, the magnetic flux concentrates on the central portion of the lower magnetic core, and There is an effect of increasing the gap magnetic field strength, and a magnetic field strength sufficient for magnetic recording can be obtained with a finer track width, so that higher density recording can be performed.

[0025]

As described above, in the thin-film magnetic head in which the overhang portion is provided on the upper magnetic core or the step is further provided on the lower magnetic core, the length of the magnetic gap of the overhang portion is made longer than the length of the magnetic gap of the track portion. By making it four times or more, the magnetic field intensity of the track portion becomes sufficient for recording on the magnetic recording medium, and the magnetic field intensity on both sides thereof is set to a low magnetic field intensity which is not erroneously recorded. Therefore, magnetic recording without writing bleeding becomes possible, and a thin-film magnetic head suitable for high-density magnetic recording can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the shapes of an upper magnetic core and a lower magnetic core as viewed from the front end of a magnetic gap of a thin-film magnetic head according to an embodiment of the present invention.

FIG. 2 is a schematic view of a cross-sectional structure of a conventional thin-film magnetic head.

FIG. 3 is a shape diagram of an upper magnetic core and a lower magnetic core of a conventional thin-film magnetic head as viewed from the front end of a magnetic gap.

FIG. 4 is a shape diagram of an upper magnetic core and a lower magnetic core of a conventional thin-film magnetic head having an upper magnetic core provided with an overhang, as viewed from the direction of a magnetic gap tip.

FIG. 5 is a diagram showing a BH curve of a magnetic recording medium.

FIG. 6 is a perspective view of a thin-film magnetic head according to an embodiment of the present invention.

FIG. 7 is a perspective view of a thin-film magnetic head according to another embodiment of the present invention.

8 is a shape diagram of an upper magnetic core and a lower magnetic core of the thin-film magnetic head of FIG.

[Explanation of symbols]

1, 5, 9, 12, 17, 22, 27 ... upper magnetic core,
2, 7, 11, 14, 20, 25 ... lower magnetic core, 3,
15, 19, 23, 30 ... wide magnetic gap, 4, 1
6, 18, 24, 29 ... narrow magnetic gap, 6, 21,
26: current coil, 8, 10: magnetic gap, 13: overhang of magnetic core.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoji Maruyama 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Central Research Laboratory (72) Inventor, Moriaki Fuyama 1-280 Higashi Koikebo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (1)

[Claims] An electric current coil is provided so that an upper magnetic core and a lower magnetic core form a magnetic circuit through a minute gap, and a current coil is disposed so as to cross the magnetic circuit. A thin-film magnetic head having a stepped surface and two long and short gap lengths, wherein the ratio of the two gap lengths is 4 or more.