Characterization of read sensors in hard disk drives

• Main Author: Liew, Li Ting.
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Materials::Microelectronics and semiconductor materials
• Online Access: http://hdl.handle.net/10356/36160
• Institution: Nanyang Technological University

One of the biggest challenges in a 10 Tb/in2 recording is the impossible reduction of the current sensor thickness to meet the linear resolution requirement, even with today’s technology. Current tunnel magnetoresistance (TMR) read head has reached its limit due to its high product of resistance and area (RA) and the shield to shield spacing (SSS) in current perpendicular-to-plane giant magnetoresistance (CPP-GMR) read head remains a bottle neck issue to achieve a high data recording. Therefore, differential dual spin valve (DDSV) is proposed to alleviate this problem, assuming that GMR ratio is not an issue. Experiments using the four probe station were executed to understand the fundamental issues associated with the DDSV structures. Hard bias was also included in the experiment to mimic the real bias field in the read sensor. The selection of the permanent magnets was depended on the simulation results via MATLAB. The samples presented in the report are classified into two groups according to the thickness differences in the spacer and gap layers. In the first group of samples, the effect of the interlayer ferromagnetic coupling effect associated with the spacer layer can be explained using the Ruderman-Kittel-Kasuya-Yosida (RKKY) and orange peel effects. Anti-ferromagnetic coupling (AFC) can be observed in the next group of samples. There is a distinct trade-off between sensitivity as well as GMR ratio when a certain thickness of the gap/spacer layer is chosen. When sensitivity of the sample is low, it will result in a high GMR ratio and vice versa.