• Ceramist
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• v.2 no.4
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• pp.35-46
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• 1999

GMR 재료의 응용은 매우 광범위하며 크게 세 분야로 대별할 수 있다. 첫째는 자기 재생 헤드로서 $10Gbit/in^2$ 이상의 고밀도 자기기록 기술에서는 필수 불가결한 재료이다. 둘째는 다양한 분야에 응용될 고감도 자기센서 분야이며, 셋째는 집접화된 자기저항메모리(MRAM) 분야이다. GMR 센서를 사용한 자기헤드는 이미 시판되고 있고 기존의 AMR 재료인 퍼멀로이에 비하여 3~20배 이상으로 신호준위가 크고 사용온도 범위에서 선형성 및 열적안정성도 우수한 것으로 보고되고 있다. MRAM의 경우에는 스핀밸브 GMR 및 TMR 소자를 사용한 연구가 한창 진행중이다. GMR 현상은 발견 된지 고작 10년 밖에 되지 않았으나 GMR 자기센서는 이미 상업적으로 개발되어 응용되고 있다. 이러한 실질적인 응용에 유리한 고지를 선점하고 있는 것은 이방성결합형 스핀밸브 다층박막 구조로서 그 내구성과 특성 향상을 위한 연구가 다양하게 시도되고 있다. GMR현상의 발견은 자성재료분야 연구 및 응용에 있어 새로운 전기를 마련하였으며 특히 자성과 이동현상이 연계된 분야로서 소위 "Magneto-electronics" 또는 "Spintronics" 라는 [51] 새로운 미래기술의 장이 열리고 있다. 현재의 반도체 중심의 "Microelectronics" 기술에서는 전자와 전자공공을 이용하는 기술이라면 "Magneto-electronics" 기술에서는 스핀${\uparrow}$ 및 스핀${\downarrow}$의 두 종류의 전자를 이용하게 된다. 자성체와 도체를 접목한 스핀 트랜지스터 또는 자성체와 반도체를 접목한 스핀-polarized FET(field effect transistor) 등의 새로운 개념의 magnetoelectronics 소자가 창출되고 있다. 따라서 자기이동 현상의 기초 연구, 재료 측면의 연구 및 헤드, MRAM, 센서 등의 응용기술연구가 국내에서 활발하게 이루어져 21세기 새로운 자성전자(magneto-electronics)소자 응용에 경쟁력을 키워야 할 것이다.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.78-83
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• 2003

Characterization of an ultra precision grinding plate for GMR head manufacturing is performed by measuring frictional forces between the grinding plate and the advanced ceramic Two kinds of methods of producing the precision grinding plates are presented: texturing and micro-channeling. Texturing is effective in terms of production time but micro-channeling excels in quality control. It is found that the frictional coefficient of a precision grinding plate decreases as the impregnation of diamond grain onto the precision-grinding plate progresses, and remains unchanged once the impregnation process is successfully completed, even after 100 revolutions of the precision-grinding plate against the advanced ceramic under 40 N of normal force. Therefore, the measurement of the frictional coefficient can replace costly and time-consuming process of estimating the level of impregnation of diamond grain on the precision-grinding plate, which has been performed by using scanning electron microscope, and be employed as an index to determine the level of impregnation of diamond grain.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.99-110
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• 1998

MR head technology from the perspective of read sensor evolution was reviewed. AMR sensors have been developed for last two decades and successfully employed into information storage devices such as disk drives. Development of manufacturable GMR sensors is of emerging technological interest because GMR sensors can further meet the need of ultrahigh recording density. In this review, the mechanisms, materials systems, operating principles of both AMR an GMR sensors, and the head structures were discuseed. Constructing GMR heads with ultrathin sensor materials and complex topographical structures demands unique fabrication and design challenges. The commercialization of GMR heads can only be realized by the succesful implementations of high performance materials, advanced thin film processes, and stable head design.

• Journal of the Korean Magnetics Society
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• v.10 no.6
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• pp.310-317
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• 2000

With use of (G)MR head, thermal asperity (TA) has been a big concern in drive industry. In this study, we investigated several factors of heads and disks which affects the TA sensitivity of the drive. TA experiments were conducted by introducing the particles on the drives using a particle injection chamber. It was found that the slider ABS shape can help to reduce TA or contamination in the head/media interface. However, TA sensitivity of the drive mainly depend on the intrinsic property of (G)MR sensor. GMR head is much less sensitive to TA compared with MR head. However, in case that the same bias current was applied for both of MR and GMR head, TA sensitivity of GMR head became almost identical to that of MR head. Therefore it was found that the bias current is a dominant factor in determining TA sensitivity of the head. TA sensitivity of different types of disks was also studied. The scratch resistance of the carbon overcoat layer is the one of the main factors which influence TA rejection capability of the disks.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.322-327
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• 2003

Giant magnetoresistance(GMR) NiO multilayer, which has been used to reading head of highly dense magnetic recording, was fabricated, and oxidized in an air during 80 days to study the dependence of magnetoresistance properties on residual stress in the interfaces. The magnetoresistance ratio and the exchange biasing $field(H_{ex})$ of $NiO(60nm)/Ni_{81}Fe_{19}(5nm)/Co(0.7nm)/Cu(2nm)/Co(0.7nm)/Ni_{81}Fe_{19}(7nm)$ spin valves were increased from 4.9% to 7.3%, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity ${\rho}$ decreased from $28{\mu}{\Omega}m$ to $17{\mu}{\Omega}m$, but ${\Delta}p$ did not almost change after the oxidation. Therefore, the increase of MR ratio is due to the decrease in the sheet resistivity. the reduced resistance may result from the increase in the reflection of conduction electrons at the oxidized top surface. Also, the increase in the exchange biasing field is originated from the reduction of residual stress at the interface of $NiO/Ni_{81}Fe_{19}$ according as the aging time increases.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.75-80
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• 2006

This paper introduces the mechanism of the ESD(electrostatic discharge) in the HDD spindle system using FDBs(fluid dynamic bearings). When a HDD(hard disk drive) spindle system is rotating, triboelectric charging occurs in the FDBs through the friction between the lubricant and the rotating shaft or between the lubricant and stationary sleeve. And this electrostatic charge is accumulated in the rotating parts of the HDD spindle system because they are insulated from the ground by the lubricant. This research shows experimentally that the behavior of electric charge and discharge in the FDB spindle system is the same as that of a capacitor. It also measures the electrostatic voltage difference between the rotating and stationary parts in the FDB spindle system due to the change of humidity, supporting load and motor speed. This research shows that the control of ESD is required in the HDD spindle system using FDBs, because the electrostatic charge accumulated in the FDB spindle system may cause the breakdown damage of the GMR head and data loss consequently.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.4
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• pp.21-26
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• 2006

Characteristics of texture and groove precision lapping plate are experimentally investigated by Measuring frictional forces. It is found that the frictional coefficient decreases as the embedding of diamond particles progresses. The groove precision lapping plate with concentric micro-channels indicates superior capability in embedding micrometer-sized diamond particles and uniformity in diamond embedding compared with the texture precision lapping plate with a series of circular micro-channels.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.154-155
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• 2002

스핀밸브형 GMR(Giant magnetoresistance) 소자는 낮은 자장범위에서 큰 자기저항변화가 생기는 높은 민감도의 소자로서, 고밀도 자기기록매체의 재생헤드 및 MRAM(Magnetoresistance Random Access Memory) 등의 실제 응용에 있어 큰 자기저항비와 열적 안정성을 가지는 재료들을 필요로 한다. NiO, a-$Fe_2O_3$, NiO/a-$Fe_2O_3$ 등과 같은 산화물의 경우, 높은 Tn(Neel temperature)을 가지므로 이를 이용한 Bottom형 스핀밸브에 대한 연구가 활발히 진행되어 왔다. (중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.318-323
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• 2005

This paper introduces the mechanism of the ESD (Electrostatic discharge) in the HDD spindle system using FDBs (Fluid Dynamic Bearings). When a HDD (Hard Disk Drive) spindle system is rotating, triboelectric charging occurs in the FDBs through the friction of the lubricant between the rotating shaft and stationary sleeve. And this electrostatic charge is accumulated in the rotating part of the HDD spindle system because it is insulated from the ground by the lubricant. This research shows experimentally that the behavior of electric charge and discharge in the FDB spindle system is the same as that of a capacitor. It also measures the electrostatic charge and discharge of the FDB spindle system due to the chanse of humidity, supporting load and motor speed. This research shows that the control of ESD is required in the HDD spindle system using FDBs, because the electrostatic charge accumulated in the FDB spindle system may cause the breakdown damage of the GMR head and data loss consequently.