Kenji Inage

ESD induced pinned layer reversal in spin-valve GMR heads

Magnetization direction of the pinned layer in the Spin-Valve giant magnetoresistive (SV) heads has been found to be reversed easily by electrostatic discharge (ESD). Thermal stress and magnetic field from ESD cause this phenomenon. This phenomenon happens only when the bias field direction by ESD current Is opposite to the magnetization of the pinned layer. The energy of magnetization reversal of the pinned layer from ESD is found to be a quarter of the ESD breakdown energy. For SV heads which consist of an AF film with higher blocking temperature, the energy becomes higher.

A performance study of next generation's TMR heads beyond 200 gb/in/sup 2/

Practical level performance for /spl sim/200 Gb/in/sup 2/ has been verified by AlOx barrier tunneling magnetoresistive (TMR) heads, which resistance area product (RA) is more than 3 ohm/spl middot//spl mu/m/sup 2/, 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/spl middot//spl mu/m/sup 2/, respectively, indicating over 200 Gb/in/sup 2/ 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/spl middot//spl mu/m/sup 2/, 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/in/sup 2/ application.

Electrical performance and reliability of tunnel magnetoresistance heads for 100-Gb/in/sup 2/ application

Tunnel magnetoresistance (TuMR) heads are attractive candidates for future high-density recording. To achieve the high areal density, it is necessary for TuMR heads to get lower resistance and higher delta R/R film. A low resistance and high delta R/R tunneling junction film has been developed and used for this study. The resistance area product and delta R/R are 3 /spl Omega//spl middot//spl mu/m/sup 2/ and 18%, respectively. Reliability that includes lifetime was also studied. We have found TuMR heads can be a promising candidate for 100 Gb/in/sup 2/ application.

Enhanced GMR ratio of dual spin valve with monolayer pinned structure

A new type of dual spin valve (DSV) structure with enhanced giant magnetoresistance (GMR) ratio is proposed, and the performance is characterized by the prototype read heads. The bottom part of DSV is kept as a synthetic pinned structure and only the top part adopts a monolayer pinned structure. The top monolayer pin DSV (TM-DSV) showed three percentage points higher GMR ratio and 20% higher /spl Delta/R value. After the mechanical lapping process, the monolayer pinned layer can be stabilized by not only sense current but also large stress induced anisotropy due to Villari effect. After the quantitative analysis, the induced stress is measured to be about 4.2/spl times/10/sup 9/ N/m/sup 2/. The bias point was tuned by adjustment of Cu spacer layer thickness using the RKKY interaction between pinned layer and free layer. There is no reliability concern related to the monolayer pinned structure. In a perpendicular magnetic recording system, TM-DSV technology could successfully demonstrate the output of 35.5 mV//spl mu/m and /spl sim/170 Gbits/in/sup 2/ density feasibility.

Reliability of tunneling magnetoresistance recording head-lifetime, failure mode, and production screening

We have studied the behavior of failure in lifetime acceleration test of TMR prototype with performance meeting 100 Gb/in/sup 2/ recording. The failure mode is identified to be same as extrinsic breakdown of the AlOx barrier, while failure due to magnetic change is not observed. The extrinsic breakdown is further found to be the increase in pinhole conduction in the barrier, involving thermal energy from ambient and read current. Results also suggest the existence of a critical voltage below which pinhole is not enlarged. Furthermore, we will discuss our hypothesis in the formation of pinholes and the role of charge traps in the barrier. Finally, we will discuss a method for screening out heads with relatively short lifetime, which is feasible for mass production. The screening allows a guarantee of lifetime well enough for drive application.

Low-frequency noise analysis of TMR heads

1/f noise as time traces of the fluctuation and low-frequency noise (pulse noise) were observed in TMR heads. These were then related to the quality of the oxide layer in the TMR heads.

ESD sensitivity and thermal stability of spin-valve read with pinned synthetic ferrimahonet

Electro static discharge (ESD) sensitivity and thermal stability of Spin Valve (SV) heads with pinned synthetic ferrimagnet (SynPin) were studied by using quasistatic tester (QST) in HGA level. Compared with conventional SV (CSV) head, SynPin SV showed better ESD endurance and thermal stability which comes from stronger pinning field at high temperature (>300/spl deg/C). Based on this paper, it is expected that SynPin SV has advantages in the SV heads fabrication process in ESD tolerance and also has more advantages in thermal reliability of SV.