• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.308.2-308.2
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• 2008

• Journal of the Korean Magnetics Society
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• v.21 no.1
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• pp.32-36
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• 2011

We fabricated a sensor for measuring the water level and water temperature using GMR-SV (giant magnetoresistance-spin valve) device, simultaneously. It could be applied to the medical cooling system of the potassium titanylphosphate KTP) laser system for the therapy of a benign prostatic hyperplasia. The middle point of GMR-SV device was set to the near position of a high magnetic sensitivity with 2.8%/Oe. The sensitivity for the water level and water temperature of the fabricated sensor were $400\;m{\Omega}/mm$ and $100\;m{\Omega}/^{\circ}C$, respectively.

• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.173-177
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• 2012

The multilayer structure of glass/Ta(5.8 nm)/NiFe(5 nm)/Cu(t nm)/NiFe(3 nm)/FeMn(12 nm)/Ta(5.8 nm) as typical GMR-SV (giant magnetoresistance-spin valve) films is prepared by ion beam sputtering deposition (IBD). The coercivity and magnetoresiatance ratio are increased and decreased for the decrease of Cu thickness when the thickness of nonmagnetic Cu layer from is varied 2.2 nm to 3.0 nm. It means that the decrease of non-magntic layer is effected to the interlayer exchange coupling of pinned layer and the spin configuration array of free layer. For experiment of detecting and dropping of magnetic beads we used the GMR-SV sensor with glass/Ta/NiFe/Cu/NiFe/FeMn/Ta structure. From the comparison of before and after for the dropping status of magnetic bead, the variations of MR ratio, $H_{ex}$, and $H_c$ are showed 0.9 %, 3 Oe, and 2 Oe, respectively. The fabrication of GMR-SV sensor was included in the process of film deposition, photo-lithography, ion milling, and MR measurement. Further, GMR-SV device can be easily integrated so that detecting biosensor on a single chip becomes possible.

• Journal of the Korean Magnetics Society
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• v.24 no.4
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• pp.101-106
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• 2014

The glass/Ta(5.8 nm)/NiFe(5 nm)/Cu(2.3 nm)/NiFe(3 nm)/IrMn(12 nm)/Ta(5.8 nm) GMR-SV (giantmagneto-resistance-spin valve) multilayer structure films with a magnetoresistance ratio (MR) of 5.0 % and a magnetic sensitivity (MS) of 1.5%/Oe was deposited by dc magnetron sputtering method. Also, GMR-SV device having a width of $7{\mu}m{\sim}8{\mu}m$ similar to the diameter of RBC (red blood cell) was fabricated by the light lithography process. When RBCs coupled with several magnetic beads with a diameter of $1{\mu}m$ dropped upon the GMR-SV device having MR = 1.06% and MS = 0.3 %/Oe, there is observed the variation of about included of a resistance value of ${\Delta}R=0.4{\Omega}$ and ${\Delta}MR=0.15%$ around a external magnetic field of -0.6 Oe. From these results, the GMR-SV device having the width magnitude of a few micron size can be applied as the biosensor for the analysis of a new magnetic property of hemoglobin inside of RBC combined to magnetic beads.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.117-122
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• 2015

The holes with a diameter of $35{\mu}m$ inside the GMR-SV (giant magnetoresistance-spin valve) film were patterned by using the photolithography process and ECR (electron cyclotron resonance) Ar-ion milling. From the magnetoresistance curves of the GMR-SV film with holes measuring by 4-electrode method, the MR (magnetoresistance ratio) and MS (magnetic sensitivity) are almost same as the values of initial states. On other side hand, the $H_{ex}$ (exchange bias coupling field) and $H_c$ (coercivity) dominantly increased from 120 Oe and 10 Oe to 190 Oe and 41 Oe as increment of the number of holes inside GMR-SV film respectively. These results were shown to be attributed to major effect of EMD (easy magnetic domian) having a region positioned between two holes perpendicular to the sensing current. On the basis of this study, the fabrication of GMR-SV applying to the hole formation improved the magnetoresistance properties having the thermal stability and durability of bio-device.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.94-100
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• 2004

We have investigated the magnetic domain structure and the thermal stability of magnetotransport properties of IrMn biased spin-valves containing Co, CoFe and NiFe. The magnetic domain structures were imaged using a magneto-optical indicator film(MOIF) technique. To investigate the thermal stability, magnetoresistance(MR) was measured at annealing temperature(TANN) and room temperature($T_{RT}$) followed by the annealing. Domain imaging reveal that the increase of annealing temperature led to changes in the exchange coupling between the two ferromagnet(FM) layers through nonmagnetic layer rather than between FM and antiferromagnet. unlike the NiFe biased IrMn spin valve with large domains, MOIF pictures of Co and CoFe biased IrMn spin valve structures show the formation of many small microdomains. The magnetic structure, as revealed by the domain images, appeared unchanged while the MR dropped dramatically. From the combined giant magnetoresistance(GMR) and MOIF results, it was apparent that the decrease of MR ratio was not related to the spin valve magnetic structure up to about $350^{\circ}C$($T_{RT}$ ).

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.35-40
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• 2010

The GMR-SV (giant magnetoresistance-spin valve) device depending on the micro patterned features according to two easy directions of longitudinal and transversal axes has been studied. The GMR-SV multilayer structure was Ta(5 nm)/NiFe(8 nm)/Cu(2.3 nm)/NiFe(4 nm)/IrMn(8 nm)/Ta(2.5 nm). The applied anisotropy direction of the GMR-SV thin film was performed under the magnitude of 300 Oe using by permanent magnet during the deposition. The size of micro patterned device was a $1\;{\times}\;18\;{\mu}m^2$ after the photo lithography process. In the aspects of the shape magnetic anisotropy effect, there are two conditions of fabrication for GMR-SV device. Firstly, the direction of sensing current was perpendicular to the magnetic easy axis of the pinned NiFe/IrMn bilayer with the transversal direction of device. Secondly, the direction of shape magnetic anisotropy was same to the magnetic easy axis of the free NiFe layer with the longitudinal direction of device.

• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.157-162
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• 2006

In this study, a high sensitive giant magnetoresistance-spin valve (GMR-SV) bio-sensing device with high linearity and very low hysteresis was fabricated by photolithography and ion beam deposition sputtering system. Detection of the Fe-hemoglobin inside in a red blood and magnetic nanoparticles using the GMR-SV bio-sensing device was investigated. Here a human's red blood includes hemoglobin, and the nanoparticles are the Co-ferrite magnetic particles coated with a shell of amorphous silica which the average size of the water-soluble bare cobalt nanoparticles was about 9 nm with total size of about 50 nm. When 1 mA sensing current was applied to the current electrode in the patterned active GMR-SV devices with areas of $5x10{\mu}m^2 $ and $2x6{\mu}m^2 $, the output signals of the GMRSV sensor were about 100 mV and 14 mV, respectively. In addition, the maximum sensitivity of the fabricated GMR-SV sensor was about $0.1{\sim}0.8%/Oe$. The magnitude of output voltage signals was obtained from four-probe magnetoresistive measured system, and the picture of real-time motion images was monitored by an optical microscope. Even one drop of human blood and nanopartices in distilled water were found to be enough for detecting and analyzing their signals clearly.

• 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 Magnetics Society
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• v.9 no.5
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• pp.251-255
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• 1999

NiFe(60 $\AA$)/Co(0$\AA$$\leq$x$\AA$$\leq$15$\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valve thin films were prepared on 4$^{\circ}$ tilt-cut Si(111) substrates with a 50 $\AA$ thick Cu underlayer without applying any external magnetic field during the deposition, and the effects of inserted ultrathin Co layer on magnetic anisotropy and GMR properties of the NiFe(60 $\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valves were investigated. As the ultrathin Co layer was inserted into the NiFe/Cu interface of the spin valves, GMR ratio was increased from about 1.5% to 3.5%, and the easy axis of NiFe(60 $\AA$) layer was rotated by 90$^{\circ}$. Accordingly, it was aligned along the same direction with the easy axis of Co(30 $\AA$)layer. Therefore, squared R-H curves was obtained in the spin valves, which is favorable properties for the digital GMR devices such as MRAM. In order to investigate the change of magnetic anisotropy of NiFe layer of the spin valves in more details,XRD measurement was performed using NiFe(500 $\AA$) and NiFe(500 $\AA$)/Co(10 $\AA$) thin films on the same templates. Strong (220) NiFe peak was observed in both films regardless of the inserted Co layer, so it was thought that the variation of magnetic anisotropy of NiFe layer is from the interface effect, the change of interface from NiFe/Cu to NiFe/Co, rather than the volume effect such as the change of magnetocrystalline effect.