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이중구조 거대자기저항-스핀밸브 박막의 자기등방성 영역분포에 관한 연구
카지드마(Purevdorj Khajidmaa),이상석(Sang-Suk Lee) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.6
The regional distribution of magnetic isotropy depending on the post annealing condition for the dual-type structure GMR-SV (giant magnetoresistance-spin valve) of NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe multilayer was investigated. The rotation of in-plane ferromagnetic layer induced by controlment of the post annealing temperature inside of the vacuum chamber. The magnetoresistive curves of a dual-type IrMn based GMR-SV depending on the direction of the magnetization easy axis of the free layer and the pinned layer are measured by between 0˚ and 360˚ angles for the applied fields. The optimum annealing temperature having a steady and isotropy magnetic sensitivity of 1.52 %/Oe was 107℃ in the rotational section of 0~90˚. By investigating the switching process of magnetization for an arbitrary measuring direction, the in-plane orthogonal magnetization for the dual-type GMR-SV multilayer can be used by a high sensitive biosensor for detection of magnetized micro-beads.
NiFe/Cu/NiFe 박막과 YBa₂Cu₃O<SUB>7−x </SUB>박막 사이 NiO 층의 두께에 따른 전류전달효과에 의한 음의 자기저항비 특성 연구
카지드마(Purevdorj Khajidmaa),강병욱(Byeong-Uk Kang),최종구(Jong-Gu Choi),이상석(Sang-Suk Lee),양우일(Woo-Il Yang) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.2
The magnetoresistance (MR) curves of giant magnetoresistive-spin valve (GMR-SV) multilayer on Corning glass and sapphire/high-temperature superconductor (HTS) YBa₂Cu₃O<SUB>7−x</SUB> (YBCO) film fabricated by magnetron sputtering were compared and analyzed. Hybrid type HTS and GMR-SV multilayer film with antiferromagnetic NiO thickness of 10 nm has a negative MR ratio of−7.7 %, an exchange coupling field (H<SUB>ex</SUB>) of 120 Oe, a coercive force (H<SUB>c</SUB>) of 125 Oe, respectively. However, there is exist a positive MR ratio of +7.3 % in case of NiO thickness of 60 nm. The glass/NiO/NiFe/Cu/NiFe/Ta multilayer showed linear current-voltage (IV) curve, but the Al₂O₃/YBCO/NiO(10 nm, 60 nm)/NiFe/Cu/NiFe/Ta multilayer showed a nonlinear I-V curve in which the resistance value of 1.15 Ω and 59.4 Ω decreased to 1.02 Ω and 50.2 Ω when the current of 15.7 mA increased to 1.67 mA, respectively. This results are explained by the current transfer effect in the 4-probe electrode measurement method occurred when the resistance of the YBCO film is 0.
GMR-SV 박막내 미크론 크기의 홀 형성을 이용한 교환결합세기와 보자력 특성연구
벌러르마(Munkhbat Bolormaa),카지드마(Purevdorj Khajidmaa),황도근(Do-Guwn Hwang),이상석(Sang-Suk Lee),이원형(Won-Hyung Lee),이장로(Jang-Roh Rhee) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.4
The holes with a diameter of 35 μm 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<SUB>ex</SUB> (exchange bias coupling field) and H<SUB>c</SUB> (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.
거대자기저항-스핀밸브와 고온초전도체 사이에 있는 틈 층에 의한 전류전달효과 특성연구
양우일(Woo-Il Yang),강병욱(Byeong-Uk Kang),최종구(Jong-Gu Choi),카지드마(Purevdorj Khajidmaa),이상석(Sang-Suk Lee) 한국자기학회 2018 韓國磁氣學會誌 Vol.28 No.5
A giant magnetoresistive - spin valve (GMR-SV) NiFe/CoFe/Cu/CoFe/IrMn/Ta multilayer film was fabricated by ion beam deposition on a commercial high - temperature superconductor Y₁Ba₂Cu₃O<SUB>7 - x</SUB> (YBCO) film. The thickness of the hybrid YBCO thin film was 300 nm and one of the antiferromagnetic IrMn-based GMR-SV thin film was 55 nm. The superconductor characteristics of the YBCO thin films were confirmed by the R-T curve measured with 4-terminal and the Q-T and I-V curves measured with a microwave cavity resonator. In particular, the phenomenon of negative magnetoresistance (MR) ratio in the reversed MR curve of -7.4% is explained by the current transfer effect from the MR and the I-V curves measured by the 2-, 3-, and 4-probe methods at 77 K below the critical temperature. It was also confirmed by SEM image that a gap layer of 9.3 nm was present between the YBCO film and the GMR-SV multilayer. The residual resistance of 0.456 Ω was measured due to the presence of the gap layer and the difference in current transfer was caused by the superconductor depending on the change of the spin magnetization array configuration of GMR-SV.
반강자성체 NiO 층 기반 단일 구조 및 이중 구조형 거대자기저항-스핀밸브 다층박막의 자기저항 특성 비교
최종구(Jong-Gu Choi),강병욱(Byeong-Uk Kang),이상석(Sang-Suk Lee),카지드마(Purevdorj Khajidmaa) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.2
GMR-SV (giant magnetoresistance-spin valve) multilayer films were fabricated on rf- and dc-magnetron sputtering systems in four different forms, in which NiO thin films were inserted into the bottom, top and middle layers. The magnetic properties of all thin film samples were investigated from the major and minor magnetoresistance curves measured at room temperature and at 77 K. The exchange coupling field (Hex) and coercivity (Hc) of the pinned NiFe layer, the Hc and interlayer coupling field (Hint), magnetoresistance ratio (MR (%)), and magnetic sensitivity (MS) of the free NiFe layer in the single-type GMR-SV multilayer with the inserted NiO layer thickness of 10 nm were 110 Oe, 115 Oe, 4.5 Oe, 6.0 Oe, 7.1%, and 1.0%/Oe, respectively. The hysteresis curves of the two free layers with the NiO thin film inserted into the middle layer formed a stable squareness ratio, which was 9.5% for the MRs of 3.5% and 6.0%, and 2.2%/Oe for the MS due to the specular and spin dependent scattering effects. On the other hand, the Hc and MS of the single structure of the bottom NiO film inserted and the dual-type GMR-SV multilayer of the bottom and top layers were greatly increased and decreased, respectively. The MRs of the GMR-SV multilayers with the magnetization of spin array configuration of the pinned layer, which is a ferromagnetic material, and the free layer are antiparallel to each other. The MR of dual-type GMR-SV multilayer showed the maximum value when the spin arrays of magnetization configuration of the pinned and free layers, is antiparallel to each other.