• 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.19 no.2
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• pp.52-56
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• 2009

Interlayer coupling field, coercivity, magnetoresitance ratio, and magnetic sensitivity depending on the thickness of free CoFe layer for the CoFe/Cu/CoFe/IrMn multilayer are investigated. In case of CoFe layer of $30\;{\AA}$ thickness for the CoFe(t)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)/IrMn($80\;{\AA}$) multilayer with ferromagnet/non-magnet/ferromagnet structure induced by IrMn layer, the lowest coercivity and the highest magnetic sensitivity, which is contained soft magnetic property, are observed. On the other side, in case of CoFe layer of $90\;{\AA}$ thickness, there are the highest coercivity and the lowest magnetic sensitivity. The fabricated CoFe($30\;{\AA}$)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)]/IrMn($80\;{\AA}$) spin valve device with $2{\times}8{\mu}m^2$ patterning size are measured by two probe method, which is selected the sensing current as the longitudinal direction and the easy axis as the transversal direction. The measuring magntoresistance ratio and magnetic sensitivity of GMR-SV device having the soft magnetic property are 3.0% and 0.3%/Oe, respectively.

• Journal of the Korean Magnetics Society
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• v.25 no.5
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• pp.162-168
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• 2015

The ${\mu}$-turn coil having a width of ${\mu}m$ on the GMR-SV (giant magnetoresistance-spin valve) device based on the antiferromagnetic IrMn layer was fabricated by using the optical lithography process. In the case of GMR-SV film and GMR-SV device, the magnetoresistance ratios and the magnetic sensitivities are 4.4%, 2.0%/Oe and 1.6 %, 0.1%/Oe, respectively. In the y-z plane the distribution of magnetic field of GMR-SV device and $10{\mu}$-turns coil which put under the several magnetic bead(MB)s with a diameter of $1{\mu}m$ attached to RBC (red blood cell) was analyzed by the computer simulation using the finite element method. When the AC currents of 20 kHz from 0.1 mA to 10.0 mA flow to the 10 turns ${\mu}$-coil, the magnetic field at the position of $z=0{\mu}m$ at the center of coil was calculated from $30.1{\mu}T$ to $3060{\mu}T$ in proportion to the current. The magnetic field at the position of $z=10{\mu}m$ was decreased to one-sixth of that of $z=0{\mu}m$. It was confirmed that the $10{\mu}$-turn coil having enough magnitude of magnetic field for the capture of RBC is possible to use as a biosensor for the detection of magnetic beads attached to RBC.

• 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.

• 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.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.210-219
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• 2000

The magnetoresistance characteristics of FeN/Co/Cu/Co and FeN/Co/Cu/Co/Cu/Co/FeN multilayers using ferromagnetic iron-nitrides (FeN) has been studied. The microstructure of FeN film is the mixed ${\alpha}$-Fe and $\varepsilon$-Fe$_3$N phase on the condition that the flow rate of N$_2$ gas is over 0.4 sccm. The magnetoresistance effect is observed because of shape magnetic anisotropy induced by needle-shaped $\varepsilon$-Fe$_3$N phase. This magnetoresistance effect changes, because the degree that the shape magnetic anisotropy adheres to the adjacent Co pinned layer is varied according to the flow rate of N$_2$ gas and the thickness of FeN film. The best magnetoresistance effect is obtained on the condition that the thickness of Co free layer is 70 ${\AA}$ and the maximum MR ratio(%) value of 3.2% shows in the FeN(250 ${\AA}$)/Co(70 ${\AA}$)/Cu(25 ${\AA}$)/Co(70 ${\AA}$)/Cu(25 ${\AA}$)/Co(70 ${\AA}$)/FeN(250 ${\AA}$) mutilayer film which is fabricated at the N, gas flow rate of 0.5 sccm and the FeN film thickness of 250 ${\AA}$. Four steps are observed in the magnetoresistance curve owing to this difference of coercive force, because respective magnetic layers in the multilayer possess different coercive forces. These effects observed in these mutilayer films can be expected to application to the memory device the same MRAM as can carry out simultaneously four signals.