• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.160-161
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• 2002

One problem in giant magnetoresistance(GMR) spin valves and magnetic tunneling junctions(MTJ) exchange biased by Mn-based antiferromagnets is the Mn diffusion into the ferromagnetic layer and other layers upon annealing.$^{1-3}$ It seems that Mn diffusion that may occur during annealing has a key role in the exchange biasing. We have fabricated multilayers inserting the nanolayer(NL) between antiferromagnet and ferromagent using ion-beam deposition system to study the diffusion effect for the exchange bias. (omitted)

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.62-63
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• 2002

To reach 100 Gbit/in$^2$ magnetic recording densities in hard disk drives specular enhancement of giant magnetoresistance (GMR) effect in spin valve (SV) films has become one of the indispensable means for application as read elements in recording heads [1]. More recently specular spin valve (SSV) structure containing nano-oxides layers (NOL) were reported [2], where MR enhancement is caused to extended mean free path of majority spin polarized electrons through specular reflection at metal/insulator interfaces [3] in the SV films. (omitted)

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.5
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• pp.421-426
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• 2008

The magnetic bio-sensor used the PHR (planar hall resistance) effect generated by the free layer in spin-valve giant magnetoresistance structure of Ta/NiFe/CoFe/Cu/NiFe/IrMn/Ta. The PHR element with micrometer size was fabricated through the photolithograph and dry etching process. The PHR signal with magnetic field was measured under the conditions of with and without single magnetic bead. A single magnetic bead of diameter $2.8\;{\mu}m$ was successfully detected using the PHR sensor. Therefore, the high resolution PHR sensor can be applied to bio-sensor application utilizing the output voltage variation of the PHR signals in the presence and absence of a single magnetic bead.

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.174-179
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• 2008

The measurement dissolution sensor system using GMR-SV device with magnetic sensitivity of 0.8 %/Oe and Mg-film thick of 200 nm and Mg-foil thick of 50 mm was fabricated and characterized. During the water dissolving process of Mg-film and Mg-foil, the subtle variation of magnetic field by the decrease of current in solenoid was detected by the GMR-SV sensor. The variations of Mg bubble number and ORP as a function of time for three different kinds of edible, tap, and distilled water, are measured and compared. A After 45 min, the speed of fast dissolving Mg was shown the order of edible > tap > DI water. The variation of output magnetoresistance as a function of dissolved time of Mg-film and Mg-foil for edible water, which is composed of mineral content of $0.8{\sim}5.4\;mg/l$ was investigated. The response times for the dissolution in edible water were 5 min and 20 min, respectively. From the measurement of dissolving time and speed for Mg-film and Mg-foil using GMR-SV device, the mineral Mg sensor system in edible water can be possible to develop.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.370.1-370.1
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• 2014

Giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and magnetic random-access memory (MRAM) are currently active areas of research. Magnetite, Fe3O4, is predicted to possess as half-metallic nature, ~100% spin polarization (P), and has a high Curie temperature (TC~850 K). On the other hand, Spinel ferrite CoFe2O4 has been widely studies for various applications such as magnetorestrictive sensors, microwave devices, biomolecular drug delivery, and electronic devices, due to its large magnetocrystalline anisotropy, chemical stability, and unique nonlinear spin-wave properties. Here we have investigated the magneto-transport properties of epitaxial CoxFe3-xO4 thin films. The epitaxial CoxFe3-xO4 (x=0; 0.4; 0.6; 1) thin films were successfully grown on MgO (100) substrate by molecular beam epitaxy (MBE). The quality of the films during growth was monitored by reflection high electron energy diffraction (RHEED). From temperature dependent resistivity measurement, we observed that the Werwey transition (1st order metal-insulator transition) temperature increased with increasing x and the resistivity of film also increased with the increasing x up to $1.6{\Omega}-cm$ for x=1. The magnetoresistance (MR) was measured with magnetic field applied perpendicular to film. A negative transverse MR was disappeared with x=0.6 and 1. Anomalous Hall data will be discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.18-23
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• 2021

There has been demand for many magnetic sensor applications, and to develop low-cost devices, it is critical to accurately understand the behavior of the magnetic field and the characteristics of magnetic sensors and target devices during initial development phase. The magnetic field has been known to have very complicated nonlinear data to calculate, so it has required expensive computing machines or research to accurately calculate the magnetic sensor values. However, this paper introduces a characteristic of a magnetic sensor called the giant magnetoresistance (GMR) and proposes simple and sufficient approaches to develop a wearable joystick device using a magnetic sensor. Particularly, this paper introduces the design factors for how to properly develop a low-cost wearable joystick device using magnetic sensors after carefully considering the mechanism of a real joystick and the characteristics of magnetic sensors. As a result, user test results are provided to show how users can operate this new wearable joystick device.

• Journal of Magnetics
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• v.13 no.2
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• pp.43-52
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• 2008

The objective of this paper is to review the magnetic and magneto-transport properties of Co/$Co_2TiSn$ consisting of two metallic magnetic phases that are antiferromagnetically exchange-coupled at the phase boundary. The bulk Co/$Co_2TiSn$ system, which has a $Co_2$TiSn Heusler alloy precipitates in the hexagonal Co matrix, showed an unusual coercivity change with a concurrent change in temperature, and was modeled on the basis of a wall formation caused by exchange coupling at the phase boundary. For measurements of magneto-transport properties, Co/$Co_2TiSn$ thin films that had two-magnet phases were deposited using a magnetron sputtering system with a composite target. The magnetization process in the films is also explained on the basis of the model of wall formation at the phase boundary. Annealed Co/$Co_2TiSn$ films showed a 0.12% GMR effect, indicating the scattering of polarized conduction electrons due to the antiparallel exchange coupling at the phase boundary. The scattering process of conduction electrons at the phase boundary was modeled with relation to the magnetization process.

• Journal of the Korean Magnetics Society
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• v.11 no.4
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• pp.141-145
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• 2001

The Mn$\_$80/Ir$\_$18.1/Pt$\_$1.9/ exchange bias layers (EBLs), which have a small amounts of Pt, exhibit a high value of H$\_$ex/. The Si/Ni-Fe/Mn$\_$80/Ir$\_$18.1/Pt$\_$1.9/ EBL shows the largest H$\_$ex/ of 187 Oe, which is equivalent to a exchange energy (J$\_$ex/) of 0.146 erg/cm$^2$. Mn$\_$80/Ir$\_$18.1/Pt$\_$1.9/ EBLS are estimated to have blocking temperature of about 250 $\^{C}$, which is higher than those of Mn-Ir EBLs and Mn-Ir-Pt EBLs with higher Pt contents. This result implies that a little addition of Pt element promotes thermal stability in the Mn-Ir-Pt EBLs. The chemical stability of Mn-Ir-Pt EBLs was characterized by potentiodynamic test, which was performed in 0.001 M NaCl solution. The current density of Mn-Ir-Pt films was gradually reduced with increasing Pt content. The present results indicate that the Mn-Ir-Pt with a small amount of Pt is suitable for an antiferromagnetic material for a reliable spin valve giant magnetoresistance device.

• Journal of Magnetics
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• v.12 no.3
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• pp.118-123
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• 2007

We have studied the effect of Au-Cu back layer system ${\sim}10{\AA}$ thick on the properties of a spin valve. The back layers were Cu, Au, co-sputtered $Cu_xAu_{1-x}$, laminated $[Au/Cu]_n$. and bi-layer [Au/Cu]. When Au was added to the Cu, the resistance of the spin valve abruptly increased most likely due to impurity scattering. The GMR values were not increased significantly for all the structures. In the case of co-sputtered $Cu_xAu_{1-x}$, the changes in the resistance, ${\Delta}R$, was increased at a composition of ${\sim}Au_{0.5}Cu_{0.5}$. This increase in ${\Delta}R$ is due to increase in the resistance and not from the enhanced spin-dependent scattering. The structural analyses showed that the orthorhombic $Au_{0.5}Cu_{0.5}$ was formed in the back layer instead of the face-centered tetragonal $Au_{0.5}Cu_{0.5}$ as we expected. Thermal annealing over $400^{\circ}C$ may be required to have face-centered tetragonal in the $10{\AA}$ thick ultra-thin film. In the case of a laminated or bi-layered back layer, the properties of the spin valve were improved, which may be attributed to the increase in the mean free path of conduction electrons.