SPIN VALVE MAGNETORESISTIVE SENSOR WITH ANTIPARALLEL PINNED LAYER AND IMPROVED BIAS LAYER, AND MAGNETIC RECORDING SYSTEM USING THE SENSOR

摘要

Spin Valve Magneto Resistive (SVMR) sensors use laminated antiparallel (AP) layers that combine with an improved antiferromagnetic (AF) exchange bias layer. The restraint layer includes two ferromagnetic layers separated by a nonmagnetic coupling layer, so that the magnetization of the two ferromagnetic layers is anti-parallel, thereby being strongly coupled to each other by antiferromagnetic properties. This laminate AP confinement layer is magnetically fixed to the small field excitation required to rotate the free layer of the SVMR sensor. The magnetic moments of the two ferromagnetic layers in this AP confinement layer are almost the same and the net magnetic moment of the bonding layer is small. However, the magnetic field is large in correspondence because it is inversely proportional to the net magnetic moment. The laminate restraint layer has a degree of magnetism that is either fixed or bonded by an AF material that is corrosion resistant but has too low Exchange Anisotropy and cannot be used in conventional SVMR sensors. In an embodiment, the AF layer is nickel-oxide and is formed on any one of magnetoresistive (MR) shields serving as a substrate. Therefore, the AF material also serves as an insulating MR gap material. The position of the laminate AP confinement layer, which is exchange coupled on the bottom surface of the AF layer and the SVMR sensor, allows the free layer to achieve an improved vertical bias when the SVMR sensor is fabricated.