• Title/Summary/Keyword: 터널링 저항

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Tunneling Magnetoresistive Properties of Reactively Sputtered $Fe/Al_2O_3/Co$ Trilayer Junctions ($Fe/Al_2O_3/Co$ 자기 터널링 접합 제작 및 자기수송현상에 관한 연구)

  • 최서윤;김효진;조영목;주웅길
    • Journal of the Korean Magnetics Society
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    • v.8 no.1
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    • pp.27-33
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    • 1998
  • We have investigated tunneling magnetoresistance (TMR) properties of Fe/$Al_2O_3$/Co magnetic trilayer junctions sputtered on single-crystal Si (001) substrates. $Al_2O_3$ layers with thicknesses of 50~200 $\AA$ were deposited directly on the bottom ferromagnetic layer by a reactive rf sputtering. For comparsion, we prepared Pt/$Al_2O_3$/Pt tunnel junctions whose current-voltage (I-V) characteristics measured at 300 K indicated that reactively sputtered $Al_2O_3$ is a particularly good material for thin insulating barriers and allows us to form pinhole-free tunnel barriers. The magnetic tunnel junctions exhibit changes of tunnel resistance of about 0.1% at 300 K with an applied magnetic field and it was found that most junctions with Co as a top electrode have rather good I-V and TMR characteristics compared to those with Fe as a electrode. These results were discussed in relation to interfacial on the basis of those for Pt/$Al_2O_3$/Pt.

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Application of resistivity monitoring with tunnel excavation area (터널 굴착에 따른 전기비저항 모니터링 기술 적용)

  • Ahn, Hee-Yoon;Jeong, Jae-Hyeung;Cho, In-Ky;Kim, Jung-Ho;Rae, Gyu-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.10 no.4
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    • pp.405-420
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    • 2008
  • Resistivity survey is one of the widely used methods for the investigation of stability of the ground or bedrock around tunnel and is also used as an essential base data for stability and reduction of construction cost through first-hand approximation of rock quality at design step. Generally, the analysis of resistivity survey data is performed by single measurement. When distribution variation of groundwater around a tunnel over time is necessary for maintenance of a tunnel, resistivity monitoring is very useful survey method to grasp distribution variation of groundwater. So we performed the grid line resistivity survey to monitoring resistivity variation for six times. And we also tried to evaluate application possibility of the resistivity monitoring for construction safety through providing detailed information on fault zones.

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AC Voltage and Frequency Dependence in Tunneling Magnetoresistance Device (터널링 자기저항 소자의 교류 전압 및 주파수 의존성 연구)

  • Bae, Seong-Cheol;Yoon, Seok Soo;Kim, Dong Young
    • Journal of the Korean Magnetics Society
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    • v.26 no.6
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    • pp.201-205
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    • 2016
  • In this report, we measured the impedance spectrum in TMR device, and the relaxation behavior of the real and imaginary impedance spectrum was analyzed by using the equilibrant circuit of tunneling capacitance ($C_T$) and tunneling resistance ($R_T$). The relaxation frequency was increased with AC voltage in both the parallel and antiparallel alignment of two magnetic layers. The $R_T$ with AC voltage showed the typical bias voltage dependence. However, the $C_T$ showed large value than the expected geometrical capacitance. The huge increase of $C_T$ was affecting as a limiting factor for the high speed operation of TMR devices. Thus, the supercapacitance of $C_T$ should be considered to design the high speed TMR devices.

Junction Area Dependence of Tunneling Magnetoresistance in Spin-dependent Tunneling Junction with Natural $Al_2O_3$Barrier (자연산화 $Al_2O_3$장벽층을 갖는 스핀의존 터널링 접합에서 자기저항특성의 접합면적 의존성)

  • 이긍원;이상석
    • Journal of the Korean Magnetics Society
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    • v.11 no.5
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    • pp.202-210
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    • 2001
  • Spin dependent tunneling (SDT) junction devices of Ta/NiFe/Ta/NiFe/FeMn/NiFe/AlOx/CoFe/NiFe/Al with in-situ naturally oxidized Al barrier were fabricated using ion beam deposition and dc sputtering in UHV chamber of 10$^{-9}$ Torr. The maximum tunneling magnetoresistance (TMR) and the product resistance by junction (R$_{j}$ A) are 16-17% and 50-60 $\Omega$${\mu}{\textrm}{m}$$^2$, respectively. The values of TMR and (R$_{j}$ A) with field annealing were slightly increased. The TMR and (R$_{j}$ A) dependence versus the junction area size was observed. These results were explained by using sheet resistance effect of bottom electrode and spin channel effects.

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Electrical and Magnetic Properties of Tunneling Device with FePt Magnetic Quantum Dots (FePt 자기 양자점 터널링 소자의 전기적 특성과 자기적 특성 연구)

  • Pak, Sang-Woo;Suh, Joo-Young;Lee, Dong-Uk;Kim, Eun-Kyu
    • Journal of the Korean Vacuum Society
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    • v.20 no.1
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    • pp.57-62
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    • 2011
  • We have studied the electrical and magnetic transport properties of tunneling device with FePt magnetic quantum dots. The FePt nanoparticles with a diameter of 8~15 nm were embedded in a $SiO_2$ layer through thermal annealing process at temperature of $800^{\circ}C$ in $N_2$ gas ambient. The electrical properties of the tunneling device were characterized by current-voltage (I-V) measurements under the perpendicular magnetic fields at various temperatures. The nonlinear I-V curves appeared at 20 K, and then it was explained as a conductance blockade by the electron hopping model and tunneling effect through the quantum dots. It was measured also that the negative magneto-resistance ratio increased about 26.2% as increasing external magnetic field up to 9,000 G without regard for an applied electric voltage.

MR Characteristics of $Al_2O_3$ Based Magnetic tunneling Junction ($Al_2O_3$를 절연층으로 이용한 스핀 의존성 터널링 접합에서의 자기저항 특성)

  • 정창욱;조용진;정원철;조권구;주승기
    • Journal of the Korean Magnetics Society
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    • v.10 no.3
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    • pp.118-122
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    • 2000
  • MR characteristics of $Al_2$ $O_3$ based magnetic tunneling juction with various $Al_2$ $O_3$ thicknesses were investigated. Spin-dependent tunneling junctions, in which the tunneling barrier $Al_2$ $O_3$ is formed by depositing a 1-3 nm thick Al layer, followed by thermal oxidation at room temperature in an $O_2$atmosphere, were fabricated on 4$^{\circ}$tilt(111)Si substrate in 3-gun magnetron sputtering system. The top and bottom ferromagnetic electrodes were Ni$_{80}$Fe$_{20}$ and Co. A maximum Tunneling MR ratio of 14% was obtained in the junction of which insulating barrier thickness was 2 nm. By increasing the tunneling voltage across the junction, maximum MR ratio reduced and finally showed no MR characteristics.s.

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Time-lapse inversion of resistivity tomography monitoring data around a tunnel (터널 주변 전기비저항 토모그래피 모니터링 자료의 시간경과 역산)

  • Cho, In-Ky;Jeong, Jae-Hyeung;Bae, Gyu-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.4
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    • pp.361-371
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    • 2009
  • Resistivity tomography is very effective geophysical method to find out the resistivity distribution and its change in time around a tunnel. Thus, the resistivity tomogram can provide helpful information which is necessary for the effective maintenance of the tunnel. However, an air filled tunnel severely distorts tomography data, especially when the current or potential electrode is placed near the tunnel. Moreover, the distortion can often lead to misinterpretation of tomography monitoring data. To solve these problem, we developed a resistivity modeling and time-lapse inversion program which include a tunnel. In this study, using the developed program we assured that the inversion including a tunnel gives much more accurate image around a tunnel, compared with the conventional tomogram where the tunnel is not included. We also confirmed that the time-lapse inversion of resistivity monitoring data defines well resistivity changed areas around a tunnel in time.

Effect of Co/Pd Multilayer on the Magnetoresistance of Perpendicularly Magnetized Magnetic Tunnel Junction (Co/Pd 다층막구조가 수직자기터널접합의 자기저항에 미치는 영향)

  • Kim, Seong-Dong;Lim, Dong-Won;Lee, Seong-Rae
    • Journal of the Korean Magnetics Society
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    • v.16 no.6
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    • pp.271-275
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    • 2006
  • We investigated the magnetoresistance of perpendicularly magnetized magnetic tunnel junction composed of Co/Pd multilayers. The magnetoresistance was maximized with Co electrodes of about 5 nm thickness, which evidenced the important role of the interface in tunneling process. Both the change in perpendicular magnetic anisotropy and improvement of junction resistance were observed with changing Co sublayers, while the spin scattering became dominant with increasing Pd sublayers.

Tunneling Magnetoresistance of a Ramp-edge Type Junction With Si3N4 Barrier (Si3N4장벽층을 이용한 경사형 모서리 접합의 터널링 자기저항 특성)

  • Kim, Young-Ii;Hwang, Do-Guwn;Lee, Sang-Suk
    • Journal of the Korean Magnetics Society
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    • v.12 no.6
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    • pp.201-205
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    • 2002
  • The tunneling magnetoresistance (TMR) of a ramp-edge type junction has been studied. The samples with a structure of NiO(60)/Co(10)/NiO(60)/Si$_3$N$_4$(2-6)/NiFe(10) (nm) were prepared by the sputtering and etched by the electron cyclotron (ECR) argon ion milling. Nonlinear I-V characteristics was obtained from a ramp-type tunneling junctions having the dominant difference between zero and +90 Oe perpendicular to the junction edge line. The voltage dependence of TMR was stable up to a bias volt of $\pm$10 V with a TMR ratio of about -10%, which may be very peculiar magnetic tunneling properties with asymmetric tunneling process between wedge Co pinned layer and NiFe free layer.