• Journal of Magnetics
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• 제8권2호
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• pp.89-92
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• 2003

The tunneling magnetoresistance (TMR) of a ramp-edge type junction with SrTiO$_3$barrier layer has been stud-ied. The samples with a structure of glass/NiO(600${\AA}$)/Co(100${\AA}$)/SrTiO$_3$(400 ${\AA}$)/SrTiO$_3$(20-100${\AA}$)/NiFe(100${\AA}$) were prepared by the sputtering and etched by the electron cyclotron (ECR) argon ion milling. Nonlinear I-V characteristics were obtained from a ramp-type tunneling junctions, having the dominant difference between two different external magnetic fields (${\pm}$100 Oe) perpendicular to the junction edge line. In the SrTiO$_3$ barrier thickness of 40${\AA}$, the TMR was 52.7% at a bias voltage of -50 mV The bias voltage dependence of resistance and TMR in a ramp-type tunneling junction was similar with those of the layered TMR junction.

• 한국재료학회지
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• 제8권3호
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• pp.263-267
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• 1998

본 연구에서는 금속 칼날 마스크와 펄스형 레이저 증착장치를 이용하여 $YBa_2Cu_3O_{7-\delta}$/$SrTiO_{3}$/$YBa_2Cu_3O_{7-\delta}$ 다층박막 형태의 In-situ SIS ramp dege 형태의 접합을 제작하였으며, 이의 특성을 조사하였다. 접합은 RSJ 형태의 전류-전압 특성ㅇ르 나타내고 있으며, 온도 변화에 따른 접합의 normal resistance는 약 $18 \omega$으로 온도에 무관하게 일정한 값을 나타내었다. 접합형태를 이용하여 감도(transfer function, dV/$d\Phi$)가 약 $22\mu$V/$\Phi_{0}$인 dc-SQUID센서를 제작하였으며, in-situ SIS ramp edge 형태의 접합이 센서로의 응용가능성을 충분히 가지고 있음을 보여 주었다.

• 한국자기학회지
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• 제12권6호
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• pp.201-205
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• 2002

경사형 모서리접합을 이용한 터널링 자기저항(tunneling magnetoresistance; TMR) 특성을 연구하였다. 박막 증착과 식각은 스퍼터링과 사이크로트론 전자공명 (electron cyclotron resonance; ECR) 장치를 각각 사용하였다. Si$_3$N$_4$ 장벽층을 이용한 접합의 다층구조는 NiO(60)/Co(10)/NiO(60)/Si$_3$N$_4$(2-6)/NiFe(10) (nm)이었다. 상하부 반강자성체 NiO에 삽입된 wedged 형태의 고정층 Co와 장벽층 Si$_3$N$_4$위에 경사진 비대칭 구조에서 자유층 NiFe간의 접합에서 일어나는 특이한 스핀의존 터널링 현상이 관찰되었다. 외부자장이 0Oe일 때와 접합경계선에 수직방향으로 90Oe일 때 측정한 접합소자의 전류전압특성 곡선이 현저하게 구별되어 나타났다. TMR의 인가 전압의존성은 $\pm$10 V일 때도 약 -10%을 유지하는 매우 안정된 자기저항 특성을 보여주었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.189-192
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• 2000

We fabricated rapid single-flux-quantum RS flip-flop circuits with and without Y$_1$Ba$_2$Cu$_3$O$_{7-{\delta}}$(YBCO) ground plane. The circuit consists of SNS-type ramp-edge Josephson junctions that have cobalt-doped YBCO and Sr$_2$AITaO$_6$(SAT) for barrier layer and insulator layer, respectively. The fabricated Josephson junction showed a typical RSJ-like current-voltage(I-V) characteristics above 50K. We sucessfuly demonstrated RS flip-flop at temperatures around 50K. The RS flip-flop fabricated on ground plane showed more definite set and reset state in voltage-flux(V-${\phi}$) modulation curve for read SQUID, which may be attributed to a shielding effect of the YBCO ground plane.

• Progress in Superconductivity
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• 제2권2호
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• pp.76-80
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• 2001

We have fabricated YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) ramp-edge Josephson junctions by modifying ramp edges of the base electrodes without depositing any artificial barrier layer. YBa$_2$Cu$_3$O/7-x//SrTiO$_3$ (YBCO/STO) films were deposited on SrTiO$_3$(100) by on-axis KrF laser deposition. After patterning the bottom YBCO/STO layer, the ramp edge was cleaned by ion-beam and then reacted with deionized water under various conditions prior to the deposition of counter-electrode layers. The top YBCO/STO layer was deposited and patterned by photolithography and ion milling. We measured current-voltage (I-V) characteristics, magnetic field modulation of the critical current at 77 K. Some showed resistively shunted junction (RSJ)-type I-V characteristics, while others exhibited flux-flow behaviors, depending on the dipping time of the ramp edge in deionized water. Junctions fabricated using optimized conditions showed fairly uniform distribution of junction parameters such as I$_{c}$R$_{n}$ values, which were about 0.16 mV at 77 K with 1$\sigma$~ 24%. We made a dc SQUID with the same deionized water treated junctions, and it showed the sinusoidal modulation under applied magnetic field at 77 K. 77 K.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.174-175
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• 2002

A ramp-type tunneling magnetoresistance (TMR) junction having structure NiO(60 nm)/pinned Co(10 nm)MiO(60 nm)/barrier SrTiO$_3$(2-10 nm)/free NiFe(10 nm) with the 15 degree slope was investigated. We obtained nonlinear I(V) characteristics for ramp-type tunneling junctions that have distinctive difference with and without applied magnetic field. In the barrier SrTiO$_3$ thickness of 4 nm, the TMR was about 52% at a bias voltage of 50 mV. (omitted)