FIG. 1 depicts an air-bearing surface (ABS) view of a conventional read transducer used in magnetic recording technology applications. The conventional read transducer 10 includes shields 12 and 18, insulator 14, hard bias structures 16, and sensor 20. The read sensor 20 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor. The read sensor 20 includes an antiferromagnetic (AFM) layer 22, a pinned layer 24, a nonmagnetic spacer layer 26, and a free layer 28. Also shown is a capping layer 30. In addition, seed layer(s) may be used. The free layer 28 has a magnetization sensitive to an external magnetic field. Thus, the free layer 28 functions as a sensor layer for the magnetoresistive sensor 20. If the sensor 20 is to be used in a current perpendicular to plane (CPP) configuration, then current is driven in a direction substantially perpendicular to the plane of the layers 22, 24, 26, and 28. Conversely, in a current parallel to plane (CIP) configuration, then conductive leads (not shown) would be provided on the hard bias structures 16. The hard bias structures 16 are used to magnetically bias the free layer 28. In an ideal case, the hard bias structures 16 match the thickness, moment, and location of the sensor layer 12.
Although the conventional transducer 10 functions, there are drawbacks. The conventional transducer 10 has a shield-to-shield spacing of SS1. In general, the shield-to-shield spacing is desired to be reduced as higher density memories are to be read. For example, the shield-to-shield spacing for the conventional read transducer 10 may be approximately twenty-two nanometers. Of this shield-to-shield spacing, approximately one-third is occupied by the AFM layer 22. The thickness of the AFM layer 22 may be reduced slightly. However, such reductions in the thickness of the AFM layer 22 adversely affect the thermal stability of the magnetoresistive sensor 20. Such instabilities in the magnetoresistive sensor 20 are undesirable.
In other conventional sensors, the AFM layer 22 is omitted, resulting in a self-pinned sensor. Such self-pinned sensors use a synthetic antiferromagnetic (SAF) structure for the pinned layer 24. A SAF structure includes two ferromagnetic layers (a reference layer and a pinned layer) separated by a nonmagnetic spacer layer. The reference layer is typically closer to the free layer than the pinned layer. Typically, the ferromagnetic layers are antiferromagnetically aligned. The self-pinned sensors rely on the magnetic coupling between the layers of the SAF for stability. However, the SAF is stable with the magnetization of the reference layer in one of two states. For example, if the pinned layer 24 were a SAF structure, the reference layer may be stable with its magnetization pointing to the left or right edge of the page. Consequently, the SAF structure may be vulnerable to reversal during use in a disk drive. Such a reversal is highly undesirable.
Accordingly, what is needed is a system and method for reducing the shield-to-shield spacing of a magnetic recording read transducer.