ROBUST DESIGN OF A PERMANENT-MAGNET STABILIZED HIGH AREAL DENSITY MAGNETORESISTIVE HEAD

As the recording industry increases areal density every year, a magnet oresistive-soft adjacent layer (MR-SAL) head design is desirable with the following qualities: easy to be fabricated in large volume, capabl e of consistent and stable device-to-device performance, and enough si gnal to noise ratio to perform at high recording densities and data ra tes. A new type of MR head with these attributes is described for an a real density equal to 1444 Mb/in.(2). The off-track characteristics of this MR head are determined by the sensor edge design which is define d by a permanent magnet (PM) layer. Improved off-track performance was achieved by substituting the spacer layer with the PM outside of the active sensor area. Excellent boundary control stabilization was obtai ned by the ferromagnetic exchange coupling between the PM and, the SAL and the MR layers. The bit error rate and electrical test results sho wed acceptable performance at 175 kbpi and 8250 tpi. The above MR head had average values of low frequency amplitude (LFA), PW50, read width and write width equal to 900 mu V, 12.4, 72, and 107 mu in., respecti vely. The low frequency symmetry (LFSYM) was 1.1 (Vpos/Vneg) and the p osition error off-track capability was 26 mu in. Finally, the LFA cova riance (sigma/avg) was found to be 0.22% and the microtrack had no bum ps or side lobes. These results indicate that this design and its impl ementation produce stable heads that can perform on and off track at 1 444 Mb/in.(2). (C) 1997 American Institute of Physics.