Victor Boris Sapozhnikov

Effect of Magnetic Field on Electrode Reactions and Properties of Electrodeposited NiFe Films

Enhancement of current for solutions, containing Ni +2 , Fe +2 , and H + ions, has been observed by linear sweep voltammetry and chronoamperometry when a magnetic field of 0.1 T was applied parallel to the cathode. The current enhancement in a magnetic field was attributed to the convection near the electrode surface induced by the Lorentz force. There is a decrease of the Fe content in NiFe films by approximately 4% obtained with applied magnetic field. It was also demonstrated that the applied magnetic field affects the magnetic properties, crystalline structure and/or texture, stress, and surface roughness of NiFe films.

2

We review the 2 Tbit/in2 reader design landscape based on existing knowledge and projection. We found that the reader signal-to-noise ratio (SNR) requirement will be highly challenging due to the rapid increase in noise and the additional requirements from assisted writing. An acceptable level of channel bit density can be achieved in spite of a slow head-to-media spacing (HMS) reduction provided that both the shield-to-shield (SS) spacing and the ¿a¿ parameter scale with the bit length. We expect the side reading control for high ktpi to be difficult, and potentially a reader side shield will be required. The reader will likely use a higher quality MgO tunneling giant magnetoresistance (TGMR) stack with improved permanent-magnet coercivity. Certain new structures such as the differential reader or the trilayer will likely be part of the solution.

{\hbox{Tbit/in}}^{2}

The current-in-plane giant magnetoresistive (GMR) trilayer readback sensor (CIP-3L), where only one permanent magnet at the back edge of the GMR stack is used to stabilize and bias a dual free layer system, is reviewed. Micromagnetic modeling is employed to show that the design has improved efficiency over abutted junction (ABJ) tunneling magnetoresistive (TMR) head designs. An experimental evaluation of how permanent magnet thickness (PM Th), interlayer exchange coupling (J), and stripe height impact the signal-to-noise ratio, symmetry, and stability of prototype CIP-3L heads is conducted. The study indicates that PM Th >400 nm, J<-0.8 erg/cm2, and a read width to SH aspect ratio of 1:1 to 0.75:1, gives optimal transfer curve performance. A head gimbal assembly spinstand comparison on perpendicular recording media with best-in-class TMR readers shows that although the amplitude of the CIP-3L heads is lower (believed to be process related), the symmetry, stability, and most important, bit-error rate normalized to electrical write width and read width, are comparable. In addition, the CIP-3L design shows better linearity and low-frequency noise performance than TMR heads. The areal density performance of the best CIP-3L heads shows 195 Gb/in2 recording capability and linear densities of 1100 kbpi

Reader Design Outlook

The interlayer in perpendicular recording affects the distance between the head and the soft underlayer (SUL, or keeper) and thus plays an important role in overall recording performance. We investigate the effect of interlayer thickness on read write processes in perpendicular recording. We show that different media designs lead to different responses during the write process. On the other hand, the effect of the interlayer thickness on the read-back process is more complicated; reducing the interlayer thickness may not necessarily lead to better performance.

Current-in-Plane GMR Trilayer Head Design for Hard-Disk Drives: Characterization and Extendibility

We suggest using a different expression for the angular dependence of the junction resistance to match the convenient definition of tunneling magnetoresistive ratio (TMR). In addition, we demonstrate that readers with high TMR have a significant intrinsic asymmetry and we suggest methods of solving the problem.