Patent Application
20070285837
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. Like reference numerals in the drawings denote like elements. In the drawings, sizes of elements are exaggerated for clarity and convenience in description.
The recording head unit 30 includes a coil 32 which serves as a source generating a magnetic field for recording; a return pole 34 which forms a magnetic path of the magnetic field generated by the coil 32; a sub-yoke 38 which forms a magnetic path of the magnetic field together with the return pole 34; and a main pole 40 which forms a magnetic path in cooperation with the return pole 34 and the sub-yoke 38 and applies the magnetic field to the recording medium 20. An air bearing surface (ABS) is defined as a plane where the recording head 30 faces the recording layer 13. In
The return pole 34 and the sub-yoke 38 are arranged around the coil 32 to form a magnetic path of a magnetic field generated from the coil 32. The sub-yoke 38 has a first end surface 38a that faces a recording layer 26 of the recording medium 20 and a first surface 38b which is perpendicular to the recording layer 26 of the recording medium. The recording medium 20 may include a recording layer 26, an intermediate layer 24 and a soft magnetic underlayer 22. The first end surface 38a is located away from the ABS. It is also located at a distance from the recording medium 20.
The main pole 40 extends along the first surface 38b of the sub-yoke 38 and further extends from the first end surface 38a of the sub-yoke 38 toward the recording medium 20. The main pole 40 has a second end surface 40a, which faces the recording layer 26 of the recording medium 20 and located in the ABS area. Also, the main pole 40 has a pole tip 43 which has a tapered end. The pole tip 43 concentrates a magnetic field to its tapered narrow end, i.e., the second end surface 40a. The pole tip 43 may have a shape which surrounds at least a portion of the first end surface 38a such that a magnetic field is condensed on the second end surface 40a. That is, the pole tip 43 has a shape such that a thickness of the pole tip 43 in a direction perpendicular to a first surface 38b of the sub-yoke 38 decreases toward the ABS. For example, the pole tip 43 has an inclined surface 40b that is inclined with respect to the first surface 38b. Also, the pole tip 43 may be in contact the entire first end surface 38a to surround the first end surface 38a such that a magnetic flux that has passed through the sub-yoke 38 is linked to the pole tip 43 without leakage to the outside. In this case, a magnetic flux that has passed through the return pole 34 and the sub-yoke 38 can be more efficiently concentrated on the second end surface 40a of the main pole.
Each of the main pole 40, the return pole 34, and the sub-yoke 38 may generally be formed of a magnetic material such as NiFe to form a magnetic path of a recording magnetic field generated from the coil 32. At this point, saturation flux density Bs of the main pole 40, the return pole 34, and the sub-yoke 38 may be controlled to have different values by adjusting the compositions of the magnetic materials of the main pole 40, the return pole 34, and/or the sub-yoke 38. Since the amount of a magnetic flux that can be condensed on the second end surface 40a of the main pole 40 is limited by the saturation flux density Bs of materials that constitute the main pole 40, return pole or sub-yoke 38, the main pole 40 may be formed of a material having greater saturation flux density Bs than that of the sub-yoke 38.
A gap g of a predetermined distance is formed between the pole tip 43 and the return pole 34 in the ABS area, so that leakage magnetic flux is generated from the second end surface 40a of the main pole 40. The recording medium 20 is a perpendicular magnetic recording medium, and has a structure of a soft magnetic underlayer 22, an intermediate layer 24, and a recording layer 26. A perpendicular component of a recording magnetic field that leaks from the second end surface 40a vertically magnetizes the recording layer 26, so that recording is performed. The recording magnetic field can be divided into a recording field Hw directed from the second end surface 40a to the recording medium 20, and a return field Hr that passes through the recording medium 20 and enters the return pole 34. A recording characteristic can be analyzed using the recording field Hw and the return field Hr. The distance (i.e., gap g) between the return pole 34 and the pole tip 43 in the ABS area, is not limited particularly as long as a magnetic field leaking from the second end surface 40a passes through the soft magnetic underlayer 22 of the recording medium 20 and constitutes a return path. In general, the gap g may be about 500 nm or less.
The read head unit 50 reading data from the recording medium 20 is further provided on a lateral side of the recording head 30. The read head unit 50 includes a first shield layer 52, a second shield layer 54, and a read sensor 56 located between the first and second shield layers 52 and 54. One end of each of the first shield layer 52, the second shield layer 54, and the read sensor 56 is formed in the ABS area. The read sensor 56 may be a magnetoresistance device such as a giant magnetoresistance (GMR) device or a tunnel magnetoresistance (TMR) device.
Table 1 compares in detail a recording characteristic of a comparison example with that of the first embodiment of the present invention by analyzing the graph illustrated in
Since the return field Hr is formed in a direction opposite to a direction of the recording field Hw, a high recording field Hw and a low return field provide an advantageous condition for recording. A magnetic field characteristic was compared using a quantity defined as Hw/Hr. A field gradient is a factor having an influence on a signal-to-noise ratio (SNR). A higher field gradient indicates good SNR characteristics.
Referring to Table 1, the magnetic recording head according to the first exemplary embodiment of the present invention, even for a case where the current is 10 mA, which was lower than the current (35 mA) of the comparison example, had a higher recording field Hw and a lower return field Hr than those of the comparison example, resulting an improvement of a field ratio by 27%. A field gradient of the inventive head was slightly lower than that of the comparison example. When a current was 35 mA, the recording field Hw of the inventive head increased by 38% and the return field Hr of the inventive head decreased by 35%, compared to those of the comparative example, which indicates an improvement of the field ratio and field gradient by 110% 5%, respectively.
A variety of exemplary embodiments of a perpendicular magnetic recording head according to the present invention will be described below. Since these embodiments are the same as the first exemplary embodiment of the present invention except for the main pole, only different parts will be described.
Table 2 compares in detail a recording characteristic of the second embodiment with that of the first embodiment of the present invention by analyzing the graph illustrated in
Referring to Table 2, when the material region 250 is formed of a magnetic material, a recording magnetic field characteristic shows a minor difference depending on the saturation flux density Bs. That is, when the material region 250 is formed of a magnetic material, the recording magnetic field characteristic has been improved compared to the comparison example discussed above. When the material region 250 is formed of Al2O3, a field gradient was very close to that of the first embodiment, and a field ratio decreased by 16% as compared to that of the first embodiment. However, even in the latter case, the recording magnetic field characteristics has improved compared to the comparison example #0 in Table 1.
In
Table 3 compares in detail a recording characteristic of the third embodiment with that of the comparison example by analyzing the graph illustrated in
Referring to Table 3, the third embodiment, where the current was 10 mA, showed 20% improved field ratio while its recording field Hw and return field Hr each were lower than those of the comparison example. Also, the third embodiment, where the current was 35 mA, had a higher recording field Hw and a lower return field Hr than those of the comparison example, indicating improvements of a field ratio and a field gradient by 92% and 3%, respectively.
The fourth embodiment illustrated in
Referring to Table 4, the fifth embodiment, where the current was 10 mA, has improved 21% of field ratio while having a lower recording field Hw and return field Hr than the comparison example. Also, the fifth embodiment, where the current was 35 mA, had a higher recording field Hw and a lower return field Hr than the comparison example, indicating improvements in a field ratio and a field gradient by 93% and 3%, respectively.
Perpendicular magnetic recording heads according to the fifth and sixth embodiments have a structure that is different from the first through fourth embodiments in that the main pole 540 or 640 of the fifth and sixth embodiments, respectively, is formed on the second surface (bottom surface) 38c of the sub-yoke 38. Since a detailed shape and material of the pole tip 543 (643) can be modified in various ways as described above in the previous embodiments and can be deduced from those embodiments, detailed descriptions and illustrations thereof will be omitted.
The present invention having the above-described construction provides a perpendicular magnetic recording head having an excellent recording magnetic field characteristic capable of providing improved high recording density by varying the design of a pole tip of a main pole.
As described above, a pole tip surrounding at least a portion of a sub-yoke is formed such that a magnetic field can be more effectively condensed on a second end surface that faces a perpendicular magnetic recording medium, so that a recording field becomes high, a return field becomes low, and a field ratio and a field gradient improve.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0051237 | Jun 2006 | KR | national |
