GB2294354A

GB2294354A - A thin film magnetic head with inclined poles

Info

Publication number: GB2294354A
Application number: GB9515131A
Authority: GB
Inventors: Woo-Young Woon
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1994-10-22
Filing date: 1995-07-24
Publication date: 1996-04-24
Anticipated expiration: 2015-07-24
Also published as: KR960015408A; DE19526399C2; GB2294354B; DE19526399A1; GB9515131D0; KR0131975B1

Description

2294354 THIN FILM MAGNETIC HEAD The present invention relates to thin film

magnetic heads for reading information from magnetic media. In particular, the invention relates to an improved thin film magnetic head design which reduces undershoot.

In a magnetic storage system, such as a computer disk drive, digital information is magnetically stored upon the surface of a magnetic medium such as a magnetic storage disk. The digital information is represented by selectively polarizing the magnetic field of consecutive areas across the surface of the rotating magnetic disk. When this information is read back from the storage disk, the magnetic polarization of the medium is sensed as an electrical output signal.

The electrical output signal is representative of both the relative strength of the magnetization in the media, and the magnetic field pattern of the read head. The digital information is represented in the existence and location of the consecutive symbols added to the electrical output signal. The read and write operations are performed by a magnetic read/write head which flies over the surface of the rotating disk.

In order to perform reliably the read and write operations with less noise, it is important for a magnetic head to have ever improving sensitivity and stable electrical characteristics. Thin film magnetic heads, which are widely used, are fabricated by a wafer process. It is well known that with thin film magnetic heads, there is no need to perform a coil winding process as employed in existing ferrite and complex beads. Further, it is well known that thin film magnetic heads have very good electrical characteristics. Such a thin film magnetic head obtains the electrical output signal from the magnetic media by forming magnetic field pattern in the direction toward the centre of a transducing gap layer which is between two poles. Through a read-back pulse (or an isolated read-back pulse) caused when the surface of the magnetic media is opposite to the transducing gap, digital information is read and written. However, such a thin film magnetic head suffers from undershoot due to the magnetic flux discontinuity between the leading edge and the trailing edge of the read-back pulse. The undershoot causes margin error when the effective digital information is closely written to the magnetic medium. Such errors provide a limit to the maximum recording density of the magnetic disk, so that the errors function as obstacles in continuing the trend towards high density and high capacity. Further, eddy current is generated in the thin film magnetic head which needs a high frequency of over 8MHz. The current damage caused due to the eddy current presents a functional limit in that the total regeneration efficiency is reduced.

A known thin film magnetic head designed to reduce undershoot is shown in Fig. 1. The thin film magnetic head of Fig. 1 uses an insulation substrate 13 compounded of A1203, and contacts the anti-saturation layers 3 and 11 of permalloy (NiFe) with the top and bottom magnetic pole layer 1 and 9, respectively, in order to reduce undershoot. The bottom magnetic pole layer 9 is formed on the surface of the insulation layer 13. In the insulation layer 7 between the top magnetic pole layer 1 and the bottom magnetic pole layer 9, conductive coils 5 such as copper are arranged. Further, magnetic flux lines 14a, 14b, and 14c are provided in a direction centring around the transducing gap layer 10 which is disposed between the top pole tip 2 and the bottom pole lip 12.

However, as seen in Fig. 1, the magnetic flux line 14a produced adjacent to the transducing gap layer 10 is dense. On the other hand, the magnetic flux lines 14b and 14c of the pole tips 2 and 12 are in a dispersion state. The discontinuity caused due to the dispersion of the magnetic flux, as shown in the graph of Fig. 1 (the graph shows amplitude of the electrical output signal according to time), leads to the undershoot US1 and USt in the leading and trailing edges of the read-back pulse RB. The undershoot US1 and USt of the leading and trailing edges are correspondingly caused to the magnetic flux discontinuity area near to the pole tips 2 and 12. As a result, it can be known that it is difficult to reduce effectively the undershoot by just using perm-alloy material.

A thin film magnetic head disclosed in a US Patent No. 5,181,152 (Applicant: Seagate Technology Inc., Title: LEADING EDGE UNDERSHOOT ELIMINATION IN THIN FILM HEADS) consists of a magnetic layer composed of NiFe having a thickness of 2-15,uM between the non-magnetic layer and the bottom magnetic pole layer so as to eliminate partial undershoot occurring in the leading edge of the read-back pulse. Further, the thin film magnetic head disclosed in this US Patent causes the magnetic layer to absorb the magnetic flux lines dispersed near to the bottom magnetic pole layer. However, such a thin film magnetic head eliminates only the partial undershoot of the leading edge of the read-back pulse. Moreover, the thicker thickness of the magnetic layer is disadvantageous in designing the thickness of the pole which is needed on the surface of the magnetic disk.

It is therefore an object of the present invention to provide a thin film magnetic head capable of eliminating undershoot caused near to the tips of the top and bottom magnetic pole layers.

It is another object of the present invention to provide a thin film magnetic head capable of reducing undershoot without extending the thickness of poles.

Accordingly, the present invention provides a thin film magnetic head having a head surface to be placed in opposition to the surface of a magnetic medium comprising top and bottom magnetic pole layers having top and bottom pole tips and separated by a transducing gap layer, in which the said top and bottom magnetic pole layers and the transducing gap layer are extended to said head surface to form a predetermined trade-off angle with the said head surface.

It is preferred that the top and bottom magnetic pole layers be of substantially equal thickness. It is also preferred that the top and bottom magnetic pole tips include at least one magnetic anti-saturation layer.

The present invention also provides a thin film magnetic head having a head surface to be placed in opposition to the surface of a magnetic medium comprising:

an insulation substrate of non-magnetic material; a bottom magnetic pole layer of a first thickness formed on the insulation layer; and layer and having a bottom pole tip and at least one magnetic anti- saturation material substrate; a transducing gap layer formed on the surface of the bottom magnetic pole a top magnetic pole layer of the said first thickness formed on an upper side of the bottom magnetic pole layer and having a top pole tip and at least one magnetic anti-saturation material layer; wherein the top and bottom magnetic pole layers and the transducing gap layer are extended to the said head surface to form a predetermined trade- off angle with the said head surface.

Preferably, the bottom magnetic pole layer comprises a first magnetic pole layer of a second thickness formed on the insulation layer and a first antisaturation layer of a third thickness formed on the surface of the first magnetic pole layer.

Preferably the top magnetic pole layer comprises a second anti-saturation layer of substantially the third thickness formed over the bottom magnetic pole layer and a second magnetic pole layer of substantially the second thickness formed on the surface of the second anti-saturation layer.

Preferably, the magnetic anti-saturation material layer included in the top and bottom pole tips are exposed to the said head surface.

A preferred value for the ratio of the said second thickness and the said third thickness is 0.25 and it is also preferred that the said trade-off angle is at least 500.

The present invention will now be described by way of example with reference to the accompanying drawings in which:

Fig. 1 is a cross sectional view of a prior thin film magnetic head and a wave form showing the read-back pulse taken along the thin film magnetic head; Fig. 2 is a cross sectional view of a thin film magnetic head according to the present invention; and Fig. 3 is a wave form showing the read-back pulse taken along the thin film magnetic head of Fig. 2.

-5 Fig. 2 is a cross sectional view of a thin film magnetic head according to the present invention. Referring to Fig. 2, a first magnetic pole layer 33 of IS,= thickness is formed on the surface of an insulation substrate 35 compounded of A1203 by a general spreading process (precipitation, deposition, or sputtering). A first anti-saturation layer 31 having the thickness of about 0.45,um is formed on the surface of the first magnetic pole layer 33. In this embodiment of the present invention, the first anti-saturation layer 31 is composed of materials such as FeCoX, which is better than NiFe in magnetic anti-saturation characteristics. A transducing gap layer 29 is formed on the surface of the first anti-saturation layer 31. The transducing gap layer 29 is contacted with a second anti-saturation layer 23 formed in the lower side of a second magnetic pole layer 21 in a location near to the outer surface of the thin film magnetic head (hereinafter, called the "head surface") which is opposite to the surface of the magnetic media 15. The head surface, as shown in Fig 2, has a first pole tip 32 (or, a bottom tip) including the exposed sections of the first magnetic pole layer 33 and the first anti-saturation layer 31, a transducing gap layer 30 corresponding to an exposed section of the transducing gap layer 29, and a second pole tip 22 (or, a top tip) including the exposed sections of the second magnetic pole layer 21 and the second antisaturation layer 23. The second magnetic pole layer 21 has a thickness of about 1.8,um equal to that of the first magnetic pole layer 33. The second antisaturation layer 23 has the thickness of about 0.45,um equal to that of the first anti-saturation layer 31. Further, there is provided an insulation layer 27 in between the second anti-saturation layer 23 and the transducing gap layer 29. In the insulation layer 27, a plurality of conductive coils 25 such as copper are formed. The coils 25 (not shown in Fig. 2) are spirally arranged to pass through the insulation layer 27.

The first and second anti-saturation layers 31 and 23 are not partially contacted with the lower side of the pole layers, like the prior art of Fig. 1, but they are extended to the head surface along the first and second magnetic pole layers 33 and 21. Further, the first and second magnetic pole layers 33 and 21 at least form a trade-off angle Ot of about 500 with the head surface in a location X. The first anti- saturation layer 31 positioned between the first and second magnetic pole layers 33 and 21, the transducing gap layer 29, and the second anti- saturation layer 23 also form the same trade-off angle ()t of about 500 with the head surface and are extended to the head surface. Moreover, the first magnetic pole layer 33 and the first anti-saturation layer 31 form one bottom magnetic pole layer 36. The second magnetic pole layer 21 and the second antisaturation layer 23 form one top magnetic pole layer 20. Therefore, the thicknesses of the top and bottom magnetic pole layers 20 and 36 are the same as each other at 2.25gm (1.8 + 0.45). That is, the thickness of the anti-saturation layer capable of improving the magnetic saturation characteristics of the poles, is 115 of the total thickness of the poles.

Referring to Fig. 3, the trade-off angle & of 500 is set to make the thickness of the pole optimal. Further, since the substantial thickness Tp of the top and bottom magnetic pole layers 20 and 36 is 2.25,um, the opposite thickness Tx of pole on the head surface opposite to the magnetic media 15 is set as 3.35,um(=2.25/cos5O). The greater the thickness opposite to the surface of the magnetic media 15, the more the magnetic flux line is dispersed. This results in increasing current damage caused due to the eddy current at high frequency. In this case, it can be understood that the opposite thickness Tx of pole of 3.35/an gives the thin film magnetic head improved magnetic saturation characteristics and also to reduces the current damage caused by the eddy current. The fact that the thickness of the pole may be small provides redundancy in fabricating the thin film magnetic head suitable for high density magnetic disks. Further, as seen in the graph of Fig. 3 (the graph shows the amplitude of the electrical output signal according to time), the magnetic line is not dispersed near to the first and second pole tips 22 and 32, so that the electrical output signal does not cause undershoot between the leading edge A and the trailing edge B of the read-back pulse RB'.

As mentioned above, in the present invention, since the occurrence of undershoot can be reduced without extension of the thickness of the pole, there is increased efficiency in providing a thin film magnetic head suitably for use in high density magnetic disks.

Although the present invention uses FeCoX as the magnetic anti-saturation material in the embodiment described. any improved magnetic antisaturation material can be used. Further, even though the trade-off angle is set as 500 and the opposite thickness of the pole is set as about 3.35ffin, it is possible to change or improve the structures related to the trade-off angle and the opposite thickness of the pole according to design conditions and general fabricating processes.

C1AIMS:

1. A thin film magnetic head having a head surface to be placed in opposition to the surface of a magnetic medium comprising top and bottom magnetic pole layers having top and bottom pole tips and separated by a transducing gap layer, in which the said top and bottom magnetic pole layers and the transducing gap layer are extended to said head surface to form a predetermined trade-off angle with the said head surface.

is 2. A thin film magnetic head according to claim 1 in which the top and bottom magnetic pole layers are of substantially equal thickness.

3. A thin film magnetic head according to claim 1 or claim 2 in which the top and bottom magnetic pole tips include at least one magnetic antisaturation layer.

4. A thin film magnetic head having a head surface to be placed in opposition to the surface of a magnetic medium comprising: an insulation substrate of non-magnetic material; a bottom magnetic pole layer of a first thickness formed on the insulation layer and having a bottom pole tip and at least one magnetic anti-saturation material substrate; a transducing gap layer formed on the surface of the bottom magnetic pole layer; and a top magnetic pole layer of the said first thickness formed on an upper side of the bottom magnetic pole layer and having a top pole tip and at least one magnetic anti-saturation material layer; wherein the top and bottom magnetic pole layers and the transducing gap layer are extended to the said head surface to form a predetermined trade-off angle with the said head surface.

5. A thin film magnetic head according to claim 4, in which the bottom magnetic pole layer comprises a first magnetic pole layer of a second thickness formed on the insulation layer and a first anti-saturation layer of a third thickness formed on the surface of the first magnetic pole layer.

6. A thin film magnetic head as claimed in claim 5, wherein the top magnetic pole layer comprises a second anti-saturation layer of substantially the third thickness formed over the bottom magnetic pole layer and a second magnetic pole layer of substantially the second thickness formed on the surface of the second anti-saturation layer.

7. A thin film magnetic head as claimed in claim 5 or claim 6, in which the ratio of the said second thickness and the said third thickness is substantially equal to 0.15.

8. A thin film magnetic head according to any one of claims 3-7, in which the magnetic anti-saturation material layer included in the top and bottom pole tips are exposed to the said head surface.

9. The thin film magnetic head as claimed in any preceding claim, in which the said trade-off angle is at least So,,.

10. A thin film magnetic head substantially as described herein with reference to Figs. 2 and 3 of the accompanying drawings.