At the heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head includes at least one coil, a write pole and one or more return poles. When current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the coil, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic media, thereby recording a bit of data. The write field then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head.
A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the magnetic media.
There is a growing demand for increased data density, which has in turn resulted in the need to form magnetic write heads with ever smaller write pole dimensions such as reduced write pole width. This reduction in write pole size results in decreased magnetic write field strength and increased risk of inadvertently writing to adjacent data tracks. In order to provide sufficient write field strength at the tip of the write pole, the write pole can be shaped with a taper so as to concentrate magnetic flux to the tip of the write pole. However, inducing a strong magnetic flux into the write pole tip in this manner can result in some of the write field leaking to the sides. This results in Adjacent Track Interference (ATI), in which a data track is simultaneously deleted by an adjacent track, and also results in Far Track Interference, in which a post recording demagnetization occurs at a position several tracks away. This can be ameliorated by forming the write pole with a bevel angle that narrows the track width of the write pole at its leading edge. However, the reduction write pole area at the media facing surface weakens the magnetic write field. The use of a magnetic shield structure, surrounding the write pole has also been shown to reduce far track interference. However, magnetic flux flowing into the side shields directly from the write pole causes field saturation and domain wall movement which also cause far track interference. Therefore, the remains a need for a write head structure that can provide a sufficiently strong write field for effective data recording, while also preventing far track and adjacent track interference.