급냉응고한 Al-Pb-X(Sn , Sn-Si) 계 합금분말의 (合金粉末) 압연판재의 (壓延板材) 제조와 소결특성

최종구,문종태,이용호,조성석 ( Jong Gu Choi,Jong Tai Moon,Yong Ho Lee,Sung Suk Cho ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.3

N/A The measurement of the apparent and tap density for Al-Pb-X(Sn,Sn-Si) powders produced by centrifugal atomizer showed that the larger theoretically calculated densities the larger those densities. And tap densities were not over 50% of the theoretical densities. The nip angle of Al-5wt%Pb alloy powders produced with 38000 r.p.m. of disk rotation was 3°degree larger than that of Al-8.5wt%Pb-3wt%Sn(-4wt%Si, 8wt%Si) with 50000 r.p.m. The effects of roll gap and rolling speed on thickness and density of the single strips by rolling were that rolling speed increasing the thickness and density of strip decreased and roll gap increasing, the thickness of strip increased but the density decresed. The compactibility of Al-Pb-X with Al by rerolling showed that the coarse powder-strips were better than fine powder-strips. From the SEM study with EDX analysis on the sintered strips, it was found that Pb and Sn were segregated with maximum size 5㎛, and Si existed surrounding the segregation zone. After sintering the clad strips at 500℃, the pores, which were spherical with 5㎛ of mean diameter, partly remained around the particles of alloy powders area, while completely disappeared at clad interface. The hardness of strips of alloy powders decreased linearly with increasing sintering temperature.

버퍼층 Ta에 의존하는 코네틱 박막의 연자성 자기저항 특성

최종구(Jong-Gu Choi),황도근(Do-Guwn Hwang),이상석(Sang-Suk Lee),최진협(Jin-Hyub Choi),이기암(Ky-Am Lee),이장로(Jang-Rho Rhee) 한국자기학회 2009 韓國磁氣學會誌 Vol.19 No.6

The property of soft magnetism for the Corning glass/non-buffer or buffer Ta/Conetic(NiFeCuMo)/Ta prepared by the ion beam deposition sputtering was studied. The effect of crystal property and post annealing treatment depending on the thickness of Conetic thin films was investigated. The coercivities of Conetic thin films with easy and hard direction along to the applying magnetic field during deposition were compared with each other. The coercivity and magnetic susceptibility of Ta(5 ㎚)/Conetic(50 ㎚) thin film were 0.12 Oe and 1.2 × 10⁴, respectively. From these results, firstly, the Conetic thin film was more soft magnetism thin film than other one such as permalloy NiFe. Secondly, the usage of soft magnetism Conetic thin film for GMR-SV (giant magneoresistance-spin valve) or MTJ (Megnetic Tunnel Junction) structure in a low magnetic field can be possible.

NiFe/Cu/NiFe/IrMn 스핀밸브 박막소자의 자화 용이축에 따른 형상 자기이방성

최종구(Jong-Gu Choi),곽태준(Tae-Joon Kwak),이상석(Sang-Suk Lee),심정택(Jung-Taek Sim) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.2

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 ㎚)/NiFe(8 ㎚)/Cu(2.3 ㎚)/NiFe(4 ㎚)/IrMn(8 ㎚)/Ta(2.5 ㎚). 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 × 18 ㎛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.

IrMn 스핀밸브 박막소자의 폭 크기에 의존하는 자장감응도

최종구(Jong-Gu Choi),이상석(Sang-Suk Lee) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.2

The Cu thickness dependence of magnetic sensitivity for the NiFe/Cu/NiFe/IrMn spin valve multilayer was investigated. The magnetic properties measured by minor MR curves for the Ta(5 ㎚)/NiFe(8 ㎚)/Cu(3.5 ㎚)/NiFe(4 ㎚)/IrMn(8 ㎚)/Ta(2.5 ㎚) multilayer is MR = 1.46 %, MS = 2.0 %/Oe, H<SUB>c</SUB> = 2.6 Oe, and H<SUB>int</SUB>= 0.1 Oe. The magnetic sensitivities of GMR-SV devices with ten different widths and a same length of 4.45 ㎛ by fabricated by photo lithography decreased from 0.3 %/Oe to 0.06%/Oe as from a width of 10 ㎛ to 1 ㎛.

원 모양 IrMn 기반 GMR-SV 다층박막에 대한 평면 홀 전압 특성 연구

최종구(Jong-Gu Choi),이상석(Sang-Suk Lee) 한국자기학회 2020 韓國磁氣學會誌 Vol.30 No.1

Planar hole resistance (PHR) and planar hole voltage (PHV) characteristics of circular IrMn-based giant magnetoresistance-spin valve (GMR-SV) type Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta multilayer films were investigated. The interlayer exchange coupling field, coerciviy, and magnetoresistance ratio of the GMR-SV multilayer were 12.0 Oe, 5.0 Oe, and 5.4%, respectively. The magnetoresistance ratio obtained from the PHR curve was 12.56% and the magnetic sensitivity was 0.63%/Oe. In the PHV curve, the linear slope (sensitive PHV, SPHV) was 120 µV/Oe due to the voltage difference of 2.4 mV in the external magnetic field ± 12 Oe. As the current value increased from 1.6 mA to 15.0 mA, both PHV and SPHV increased linearly. As a method of improving the sensitivity of the PHR sensor, it is proposed to control the thickness of the Cu layer which can reduce the interchange coupling force in the GMR-SV multilayer.

강자성층 사이에 초연자성 NiFeCuMo 중간층을 삽입한 3층 박막구조의 자기적 특성

최종구(Jong-Gu Choi),이상석(Sang-Suk Lee) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.4

Two-layered ferromagnetic alloy films (NiFe, CoFe) with a Conetic (NiFeCuMo) intermediately soft magnetic layer of different thickness were investigated to correlate the coercivity values and magnetization process with the strength of saturation field of hard axis. Thickness dependence of the H<SUB>EC</SUB> (coercivity of easy axis), H<SUB>HS</SUB> (saturation field of hard axis.), and χ (susceptibility) of NiFe and NiFeCuMo thin films for the glass/Ta(5 ㎚)/[CoFe or NiFe(5 ㎚-t/2)]/NiFeCuMo(t = 0, 4, 6, 8, 10 ㎚)/[CoFe or NiFe(5 ㎚-t/2)]/Ta(5 ㎚) films prepared by the ion beam deposition method was measured. The magnetic properties H<SUB>EC</SUB>, H<SUB>HS</SUB>, and χ of two-layered ferromagnetic CoFe, NiFe films with a NiFeCuMo intermediately super-soft magnetic layer were strongly depended on the thickness of NiFeCuMo layer. The value of the coercivity and magnetic susceptibility of the NiFeCuMo film decreased by 25% and doubled relative to that of the NiFe film.

미크론 자성비드 검출용 바이오센서에 대한 고감도 GMR-SV 소자의 제작과 특성 연구

최종구(Jong-Gu Choi),이상석(Sang-Suk Lee),박영석(Young-Seok Park) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.5

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, Hex, and Hc 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.

CoFe/Cu/CoFe/PtMn 다층박막의 자기저항 곡선을 이용한 자기 등방성 특성 분석

최종구(Jong-Gu Choi),김수희(Su-Hee Kim),최상헌(Sang-Heon Choi),이상석(Sang-Suk Lee),이장로(Jang-Roh Rhee) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.4

The magnetic isotropy property from the magnetoresistance (MR) curve and magnetization (MH) loop for the PtMn based spin valve (SV) multilayer films fabricated with different the bottom structure after post-annealing treatment was investigated. The exchange biased coupling field (H<SUB>ex</SUB>), coercivity (H<SUB>c</SUB>), and MR ratio of Glass/Ta(10 ㎚)/CoFe(6 ㎚)/Cu(2.5 ㎚)/CoFe(3 ㎚)/Ta(4 ㎚) SV multilayer film without antiferromagnetic PtMn layer are 0 Oe, 25 Oe, and 3.3 %, respectively. MR curve for the Glass/Ta(10 ㎚)/CoFe(6 ㎚)/Cu(2.5 ㎚)/CoFe(3 ㎚)/PtMn(6 ㎚)/Ta(4 ㎚) SV multilayer film showed H<SUB>ex</SUB> = 2 Oe, H<SUB>c</SUB> = 316 Oe, and MR (%) = 4.4 % with one butterfly MR curve having by the effect of antiferromagnetic PtMn layer. MR curve for the dualtype Glass/Ta(10 ㎚)/CoFe(6 ㎚)/Cu(2.5 ㎚)/CoFe(3 ㎚)/PtMn(6 ㎚)/CoFe(3 ㎚)/Cu(2.5 ㎚)/CoFe(6 ㎚)/Ta(4 ㎚) SV multilayer film showed H<SUB>c</SUB> = 37.5 Oe and 386 Oe, MR = 3.5 % and 6.5 % with two butterfly MR curves and square-like hysteresis MH loops. The anisotropy property in CoFe spin valve-PtMn multilayer is neglected by the effects of a very small value of H<SUB>ex</SUB> and a very slightly shape magnetic anisotropy. This result is possible to explain the effect of magnetization configuration spin array of the bottom SV film and the top SV film of PtMn layer.

바이오센서용 3가지 나선형 코일과 이중구조 GMR-SV 소자 제작과 특성 연구

최종구(Jong-Gu Choi),정훈모(Hoon-Mo Jung),이상석(Sang-Suk Lee) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.6

We fabricated the GMR-SV device composed of three helical coils, for application as biosensors using by lithography. Ar-ion milling, and lift-off processes. Three different helical coils of Cu films were placed on the center of the GMR-SV with a width of 2 ㎛. A SiO₂ film of 100 nm thick was deposited as a insulating layer so that the center of the lower helical coil layer and the upper layer of coil electrode was separated. When the same dc current of 10 mA was applied to the coils of 2 turn, 3 turn, and 4 turn, the maximum magnetic flux density values at the center z = 0, which is perpendicular to the coil plane, were 1820 μT, 2400 μT and 3090 μT, respectively. The magnetoresistance ratio of the GMR-SV device measured with two terminals was 2.08 %, but it had almost linear hysteresis property and the average magnetic field sensitivity was 0.2%/Oe or less. When multiple magnetic beads adsorbed on the surface of red blood cells pass through a 8 ㎛ width of PR channel, the currents induced to the respective coils of three multi-turns are generated as an enough magnetic field to capture those. After stopping the red blood cells, there is a possibility that the output signal value of the GMR-SV device as bisosenor can be detected.

[NiFe/NiFeCuMo/NiFe]/FeMn 다층박막의 교환결합력과 보자력에 관한 특성 연구

최종구(Jong-Gu Choi),이상석(Sang-Suk Lee) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.4

The exchange bias field (H<SUB>EX</SUB>) and the coercivity (H<SUB>C</SUB>) variation and change depending on the thickness of intermediately super-soft magnetic NiFeCuMo layer with different thickness of the bottom NiFe layer were investigated. The H<SUB>EX</SUB> of triple pinned NiFe(4 ㎚)/ NiFeCuMo(<SUB>tNiFeCuMo</SUB>= 1 ㎚)/NiFe(4 ㎚)/FeMn multilayer has the maximum value more less than one of single pinned NiFe(8 ㎚)/ FeMn layer. If NiFeCuMo layer is inserted each into between the pinned and free NiFe layers, we can be used as GMR-SV device for a bio-sensor that has improved magnetic sensitivity.