Magnetic storage devices (e.g., hard disk drives, etc.) typically use an inductive ring head to write data using magnetic fields on a recording medium. Longitudinal storage systems typically write the magnetic elements such that the polarity of the magnetic elements is parallel with the surface of the recording medium. Perpendicular recording systems typically write the data such that the polarity of the magnetic elements are perpendicular to the surface of the recording medium and therefore more dense. FIG. 1A shows an exemplary perpendicular recording system.
Perpendicular recording system 151 comprises a write head (e.g., a monopole inductive element) having a main pole 152 and a return pole 153. When a current is passed through the coil of the main pole 152 a field 154 is created. In a typical perpendicular recording system, a soft underlayer 159 is disposed beneath recording medium 158 and creates a return path for field 154 to return to return pole 153. Depending upon the polarity of a field 154, a magnetic elements (e.g., 156 and 157) is altered on recording medium 158. For example, the polarity of field 154 causes the north pole and south pole of element 156 to be aligned in a first direction. However, changing the polarity of field 154 when writing element 157 results in an opposite polarity so that the north pole and south pole are aligned in an opposite direct on to that of element 156.
Perpendicular storage systems facilitate greater storage density and improved bit detection and error correction characteristics over longitudinal systems. However, the soft underlayer (e.g., 159) creates problems with data erasure which were not generally encountered with longitudinal recording systems. Referring again to FIG. 1A, when a longitudinal external field (e.g., HIon 160 of FIG. 1A) is applied, soft underlayer 159 accentuates the collection of magnetic charges in the corners of structures, such as the recording head, which are in general contact with the air bearing surface. This can result in unwanted stray magnetic fields at those corners which can potentially erase stored data from recording medium 158.
FIG. 1B shows a top view of perpendicular recording, head 151. As shown in FIG. 1B, the magnetic flux becomes more focused in the region of perpendicular recording head 151. More specifically, the flow of the magnetic flux is focused at the corners (e.g., 181, 182, 183, and 184) of perpendicular recording head 151. Accordingly, magnetic charges gather at the corners (e.g., 181, 182, 183, and 184) of the recording head and can result in corner stray magnetic fields which can write on unwanted tracks or other locations, thereby erasing data from the storage medium.
FIG. 2 is a top view of an exemplary recording head. In FIG. 2, recording head 151 has beveled edges 190 and 191 on the corners of the surface which is exposed to the air bearing surface. It has been found that beveling the edges (e.g., beveled edges 190 and 191) of the recording head can reduce the amount of magnetic charge that can accumulate proximate to the storage medium. Instead, the build up of magnetic charges is generally in the regions of corners 190a and 191a. Furthermore, it has been found that a shallow angle of 10° or less (e.g., angle Θ of FIG. 2) is preferable to reduce the build up of magnetic charges proximate to the recording medium.
However, fabricating a recording head with the cross section shown in FIG. 2 is difficult and often prone to manufacturing errors. For example, if recording head 151 is maintained at a fixed width, the shallow angle of beveled edges 190 and 191 reduces the useful area (e.g., region 197) of recording head 151 to an unacceptable dimension. Alternatively, if the useful area of region 197 is widened to an acceptable dimension, the overall width of recording head 151 may be unacceptable.
Additionally, when the bottom surface of recording head 151 is being defined during fabrication, precise alignment of the definition mask is required. If the definition mask is mis-aligned, too much of the bottom surface of the recording head 151 may be removed, typically indicated by line 195, thus eliminating the beveled edges. For example, an error of as little as 0.5μ can eliminate the beveled edges from the beveled recording head. As a result, the advantage of beveling edges 190 and 191 is lost and unwanted stray magnetic field effects may be exhibited by recording head 151.