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Liu X.,Central South University | Yu Z.,Central South University | Wei Q.,Central South University | Wen G.,SAE Technologies Development Co. | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects

Polycrystalline nanodiamonds (NDs) derived from shock wave synthesis exhibits serious agglomeration in non-polar medium such as clean oil. Here we report an efficient new approach to modify the NDs by exposing the nanoparticles to periodic magnetic field (PMF) enhanced hydrogen plasma in the gas phase. The modification treatment transforms oxygenated groups on the NDs surface into C H terminations. The evolution of polycrystalline NDs has been carefully characterized by FTIR, Raman and XRD analysis and the enhancement mechanism of PMF was discussed. After this treatment, well-dispersed and stable suspensions of diamond nanoparticles in clean oil with average diameter of 74.7 nm can be obtained. Subsequent nanogrinding of thin-film magnetic heads (TFH) validates their dispersion behavior. A smooth substrate (Ra ~ 0.387 nm) surface and a planar recording surface (PTR ~ 0.048 nm) were achieved. © 2012 Elsevier B.V. Source

Bai W.,SAE Technologies Development Co. | Teng Z.,SAE Technologies Development Co. | Teng Z.,Shanghai JiaoTong University | Liu R.,SAE Technologies Development Co. | And 3 more authors.
Electrical Overstress/Electrostatic Discharge Symposium Proceedings

This paper presents Machine Model (MM) discharge to TMR HGA in different ways, including stressing between the two read pads, and between one read pad and ground. The breakdown voltage is 0.89 V and 6.0 V respectively. The discharge voltage at the TMR sensor in MM stress test is measured and simulated for each case. The discharge voltage at the TMR sensor is inversely proportional to the interconnect window percentage in the later case. Increasing the window percentage in the reference plane can effectively improve threshold voltage of the TMR sensor when MM stressing between one read pad and ground. © 2011 ESD Association. Source

Zheng F.,SAE Technologies Development Co. | Teng Z.,SAE Technologies Development Co. | Song C.,SAE Technologies Development Co. | Zhang Y.,SAE Technologies Development Co. | Chen C.,SAE Technologies Development Co.
IEEE Transactions on Device and Materials Reliability

This paper experimentally presents the permanent-shunt resistance (PSR) effect on electrostatic discharge (ESD) threshold of a MgO-based tunnel magnetoresistance reader with an ultralow resistance-area (RA) barrier. Parallel-connected permanent shunts of different values are designed for the experiment. The PSR shunt can improve the ESD threshold, but it also brings some degradations on the dynamic performance of the read signal, and a tradeoff is needed between the ESD protection and the read signal. 'Barrier defect enlargement' mode was found effective to explain the ESD damage mechanism in the low RA reader, and the slope factor between normalized amplitude and normalized magnetic reader resistance is related to the PSR value strongly. Based on the RA value, PSR shunt value, and slope factor between normalized amplitude and normalized magnetic reader resistance, the RA of the defective area can be determined to be around one quarter of RA of the magnetic tunnel junction RA. © 2014 IEEE. Source

Su L.,SAE Magnetics H.K. Ltd. | Hu Y.,SAE Technologies Development Co. | Lam E.L.,SAE Magnetics H.K. Ltd. | Li P.,SAE Technologies Development Co. | And 6 more authors.
IEEE Transactions on Magnetics

As the areal recording density approaches to 1 Tb/in2, the spacing between magnetic heads and medium is decreased to sub-1-nm regime with the application of dynamic flying height (DFH) technology. Challenges in tribological flyability and reliability in the head-disk interface (HDI) become formidable at such ultra-low spacing, and it is necessary to achieve from both media and head design. It is also essential to have a better touch-down (TD) detection method and more accurate back-off spacing control for sustainable tribological performances. In this paper, the dynamics and wear during TD process were studied first. The characteristic TD modes were identified by laser Doppler vibrometry (LDV) and the TD induced wear was quantified using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that different TD stages correspond to different TD modes and amount of TD wear. It is found that the identification and capture of the characteristic TD modes, especially the first TD mode, are the key factors to timely detect TD and minimize the TD wear. The tribological performances at sub-1-nm clearance were then investigated with respect to both head and media design. The slider dynamics over a bump was studied to simulate the head reliability when the head intermittently contacts the media. It is found that air bearing surface (ABS) design of the head has a significant influence on the settling time when head passes through the bump. In addition, the flyability over a wavy surface (i.e., media run-out) was also studied to understand the TD repeatability. The results show that media run-out strongly affects TD repeatability and back-off spacing accuracy. Consequently, spacing control to sustain the reliability at sub-1-nm clearance is necessary. With in-depth understanding of dynamics and tribological performances (i.e., flyability and reliability), media and head ABS design are the key factors to achieve a sustainable HDI at sub-1-nm clearance. © 2006 IEEE. Source

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