1. Field of the Invention
The present invention relates generally to media write heads having at least one floating side shield and, in particular embodiments, to disk drive write heads with floating side shields that reduce fringe field effects on neighboring tracks during the performance of a write operation, and methods to manufacture such write heads.
2. Related Art
Disk drives are used in a variety of electronic devices, ranging from personal computers to portable media players, for the storage and retrieval of data. In a disk drive, data is typically written to and read from magnetic storage media called disks. A disk drive typically comprises a plurality of disks for the storage of data and one or more read/write heads for the reading and writing of data. There is a constant market demand to increase the data storage density of disks. Increasing the storage density of the disks can decrease the price to storage-capacity ratio of the disk drives, increase performance, and decrease the physical dimensions of the disk drive.
The write head typically comprises a pole tip, a yoke supporting the write pole tip, and conductive coils around the yoke for electrically magnetizing the write pole tip. During a write operation where the disk drive changes the storage state of a bit of data on the disk, the write head is moved to the location of the bit of data such that the pole tip is positioned directly above the bit, an electric current is passed through the coils to magnetize the pole tip, which in turn causes the magnetization of the bit to change.
In recent years, perpendicular recording has been introduced to achieve greater data storage density for disk drives. In perpendicular recording, the magnetization of each bit is aligned vertically, perpendicular to the disk surface. Compared to longitudinal recording, a perpendicular recording system allows more data bits per unit of disk surface area, which in turn enables greater data storage density for the disk drives.
On the surface of a disk, the data bits are arranged in concentric circles called tracks. As the area needed for each bit decreases, the track width also decreases, thus increasing the number of tracks per inch and the storage density of the disk. However, as the tracks become more closely spaced, a problem arises when the fringe magnetic field emitted by the write pole tip during a write operation affects the magnetic storage state of bits on a neighboring track. The fringe field can cause inadvertent erasures on neighboring tracks, or enhance thermal decay of adjacent tracks. These effects could cause data loss, a decrease in data storage reliability, or catastrophic failures to the disk drive.
In light of the problem discussed above, it is therefore preferable to have a write head design that reduces the fringe fields emitted by the write pole tip. One method of producing such a write head is proposed by U.S. Pat. No. 4,935,832, which discloses side shields connected to a downstream pole of the write head for the reduction of fringe fields emitted from the write pole tip.
The side shield design disclosed in U.S. Pat. No. 4,935,832 is difficult to manufacture due to the difficulty in controlling the gap distance between the side shields and the write pole tip, in addition to the need to define the gap distance between the write pole tip and the write shield (return shield). Since the write pole tip and the write shield (to which the side shields are attached to) are manufactured in separate steps, it is impractical to accurately define the gap distances between the write pole tip, write shield, and side shields using the current manufacturing techniques.
In addition, the structure disclosed in U.S. Pat. No. 4,935,832 has another disadvantage of creating magnetic flux leakage from the write pole tip. During a write operation, the write pole tip is highly magnetized and thus have a relatively high magnetic potential (V_WP). The magnetic potential of the write shield (return shield) is usually at a very low value creating a return path for the magnetic flux. Since the side shields and the write shield are connected, the side shields have substantially similar magnetic potentials as the very low magnetic potential of the write shield. Hence, there is likely a leakage of magnetic flux from the write pole tip to the side shields. This side-shield leakage is proportional to the difference between the potential of the write pole tip (V_WP) and the potential of the side shields (V_SS). During a write operation, this potential difference between V_WP and V_SS can be large, causing a large amount of magnetic flux leakage from the write pole tip to the side shields. This flux leakage decreases the overall efficiency of the write head because more current is needed to induce sufficient magnetic field to achieve the write operation. The side-shield leakage is also inversely proportional to the gap distance between the side shield and the write pole tip. Thus, increasing the gap distance between the side shield and the write pole tip can reduce side-shield leakage. However, if this gap distance is larger than the track-to-track pitch of the disk, the side shield will cease to protect adjacent tracks from fringe field effects. Therefore, using a design in which the side shields are connected to and magnetically coupled with the write shield, magnetic flux leakage from the write pole tip to the side shields is likely unavoidable.
Therefore, embodiments of the present invention relate to creating a write pole tip with side shields which reduces fringe field effects on adjacent tracks but also reduces side-shield leakage, utilizing a manufacturing process easily controllable with the current manufacturing techniques.