A performance study of next generation´s TMR heads beyond 200 gb/in2

Practical level performance for ∼200 Gb/in² has been verified by AlOx barrier tunneling magnetoresistive (TMR) heads, which resistance area product (RA) is more than 3 ohm·μm², in perpendicular recording mode. In addition, improved AlOx barrier magnetic tunnel junctions (MTJs) formed on plated bottom shield with smoothed surface achieved TMR ratio of 25% and 16% with RA of 1.9 and 1.0 ohm·μm², respectively, indicating over 200 Gb/in² is also possible by the AlOx barrier TMR heads with lower RA. Furthermore, TMR heads with crystalline MgO barrier were fabricated. The MgO barrier MTJs formed on plated bottom shield with smoothed surface achieved TMR ratio of 88% with RA of 2.0 ohm·μm², which is 3.5 times higher than that of AlOx barrier MTJs under similar RA. Dynamic electrical test was also performed for TMR heads with the MgO barrier. As a result, good readback waveform with huge output was obtained. This is the first confirmation of readback waveform generated from TMR heads with crystalline MgO barrier. Our results indicate that the future of TMR heads technology is promising beyond 200 Gb/in² application.