• 한국자기학회지
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• 제3권3호
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• pp.229-233
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• 1993

광자기 디스크의 제조시 기록막내부의 산소함량에 따른 기록 및 자기적 특성의 변화를 연구하였다. 기록막내의 산소함량 변화는 반응성 스퍼터링에 의해 조절하였으며 스퍼터링 전과정 동안 산소의 거동을 in-situ 잔류가스분석기로 조사하였다. 산소함량의 증가에 따라 보자력은 감 소하였으나 수직이방성 및 수직 각형비등은 변화하지 않았다. 대부분의 첨가된 산소는 스퍼터링 과정중 소모되어 Tb원자와 안정한 산화물을 형성하여 자기적 조성의 변화를 초래하였지만 임계기 록크기와 임계외부자계크기에만 약간의 변화를 가져왔을 뿐 디스크의 기록신호잡음비에는 별로 영향을 미치지 않았다. 또한 디스크의 신뢰도면에서도 크게 감소하지 않았다.

• Journal of Magnetics
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• 제7권3호
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• pp.80-93
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• 2002

The role of magnetic anisotropy of the antiferromagnetic layer on the magnetization process of exchange coupled polycrystalline ferromagnetidantiferromagnetic bilayers is discussed. In order to elucidate the magnetic torque response of Ni-Fe/Mn-Ir bilayers, the single spin ensemble model is newly introduced, taking into account the two-dimensionally random distribution of the magnetic anisotropy axes of the antiferromagnetic grains. The mechanism of the reversible inducement of the exchange anisotropy along desirable directions by field cooling procedure is successfully explained with the new model. Unidirectional anisotropy constant, J$k$, of polycrystalline Ni-Fe/Mn-Ir and Co-Fe/Mn-Ir bilayers is investigated as functions of the chemical composition of both the ferromagnetic layer and the antiferromagnetic layer. The effects of microstructure and surface modification of the antiferromagnetic layer on JK are also discussed. As a notable result, an extra large value of J$k$, which exceeds 0.5 erg/cm$^2$, is obtained for $Co_{70}Fe_{30}Mn_{75}Ir_{25}$ bilayer with the ultra-thin (50${\AA}$∼100${\AA}$) Mn-Ir layer. The exchange anisotropy of $Co_{70}Fe_{30}$ 40 ${\AA}/Mn_{75}Ir_{25}$ 100 ${\AA}$ bilayer is stable for thermal annealing up to $400{^{\circ}C}$, which is sufficiently high for the application of spin valve magnetoresistive devices.

• 한국세라믹학회지
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• 제44권6호
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• pp.308-312
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• 2007

Ferroelectric, magnetic, and magnetoelectric effects for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics have been investigated. The data show that magnetoelectric polarization coefficient, ${\alpha}_p$ is due to a linear coupling between polarization and magnetization, and that ${\alpha}_p$ is independent of dc magnetic bias and ac magnetic field. The values of ${\alpha}_p$ and magnetic induced susceptibility for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics are much larger than those of single $BiFeO_3$ crystal. We believe that the magnetoelectric effect is significantly enhanced by breaking of the cycloidal spin state of a long-period spiral spin structure due to randomly distributed charged imperfections.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.5-32
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• 2000

MRAM, High performance MRAM using MTJS demostrated, fully integrated MTJ MRAM with CMOS circuits, write time ~2.3 nsec; read time ~3 nsec, Thermally stable up to ~350 C, Switching field distibution controlled by size & shape. Magnetic Tunnel Junction Properties, Magnetoresistance: ~50% at room temperature, enhanced by thermal treatment, Negative and Positive MR by interface modification, Spin Polarization: >55% at 0.25K, Insensitive ot FM composition, Resistance $\times$ Area product, ranging from ~20 to 10$^{9}$ $\Omega$(${\mu}{\textrm}{m}$)$^{2}$, Spin valve transistor, Tunnel injected spin polarization for "hot" electrons, Decrease of MTJMR at high bias originates from anode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.212-212
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• 2010

최근 차세대 반도체 메모리 소자로 대두된 magnetic random access memory(MRAM)에 대한 연구가 활발히 진행되고 있다. 특히 MRAM의 magnetic tunnel junction(MTJ) stack을 구성하는 자성 재료의 건식 식각에 대한 연구에서는 좋은 profile을 얻고, 재층착의 문제를 해결하기 위한 노력이 계속해서 진행되고 있다. 본 연구에서는 photoresist(PR)과 Ti 하드 마스크로 패턴 된 배리어(barrier) 층인 MgO 박막의 식각 특성을 유도결합 플라즈마를 이용한 고밀도 반응성 이온 식각(inductively coupled plasma reactive ion etching-ICPRIE)을 통해서 연구하였다. PR 및 Ti 마스크를 이용한 자성 박막들은 HBr/Ar, HBr/$O_2$/Ar 식각 가스의 농도를 변화시키면서 식각되었다. HBr/Ar 가스를 이용 식각함에 있어서 좋은 식각 조건을 얻기 위한 parameter로서 pressure, bias voltage, rf power를 변화시켰다. 각 조건에서 Ti 하드마스크에 대한 터널 배리어층인 MgO 박막에 selectivity를 조사하였고 식각 profile을 관찰하였다. 식각 속도를 구하기 위해 alpha step(Tencor P-1)이 사용되었고 또한 field emission scanning electron microscopy(FESEM)를 이용하여 식각 profile을 관찰함으로써 최적의 식각 가스와 식각 조건을 찾고자 하였다.

• 한국자기학회지
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• 제1권2호
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• pp.31-36
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• 1991

스퍼터링에 의해 형성된 비정질 Co/sub 87/Zr/sub 4/Nb/sub 9/ 박막을 TEM과 EDS로 분석하여 박막의 구조적 그리고 저성적 불균일성을 관찰하였다. 특히 기판 bias를 가한 상태에서 제조된 박막을 회전 자장 열처리했을 때는 Co-rich 지역과 (Zrnb) oxied-rich 지역의 조대한 조직으로 분리되었으며, 이러한 박 막의 자기적 특성은 'ultra-soft'한 성질을 나타내었다. Ulta-soft함 박막은 H/sub c/=0.18 Oe, H/sub k/ = 0.55 Oe, M/sub r//M/sub s/=0.75의 자기적 특성과 overdamping된 고주파특성, 그리고 외부자계에 대한 자화율 변화곡선이 가역적이고 연속적이라는 특이한 현상을 보인다. 조성적으로 불균일한 박막의 ultra-soft 한 특성은 Co-rich 입자들이 exchange coupling energy와 magnetostatic coupling energy를 최소화 하기 위해 만드는 vortex형의 자화분포로써 설명되었다. 즉 vortex 는 여러개의 co-rich 입자들로 형성 되어있는 것으로 추정되며, 수평, 수직방향으로의 반자장 계수(demagnetizing factor)가 각각 flux closure 와 flux reversal에 의해 무시되기 때문에 vortex로 부터 CoZrNb 박막의 ultra-soft 특성을 설명할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.546-549
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• 2003

The principle of the superconducting vortex flow transistor (SVFT) is based on control of the Abrikosov vortex flowing along a channel. The induced voltage is controlled by a bias current and a control current, instead of external magnetic field. The device is composed of parallel weak links with a nearby current control line. We explained the process to get an I-V characteristic equation and described the method to induce the external and internal magnetic field by the Biot-Savarts law in this paper. The equation can be used to predict the I-V curves for fabricated device. From the equation we demonstrated that the current-voltage characteristics were changed with input parameters. I-V characteristics were simulated to analyze a SVFT with multi-channel by a Matlab program.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.260-263
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• 2002

There is great interest in developing magnetoresistance(MR) sensor, using ferromagnetic, electrically non-magnetic conducting and antiferromagnetic films, especially for the use in weak magnetic fields. Here, we report single and Wheatstone-bridge type of MR sensors made in Si(001)/NiO($300{\AA}$)/NiFe bilayers. Angular dependence of MR profiles was measured in Si(001)/NiO($300{\AA}$)/NiFe($450{\AA})$ films as a function of an angle between current and applied field direction, also, linearity was determined. AMR characteristics of single MR sensors was well explained with single domain model. Good linearity in $45^{\circ}$ Wheatstone-bridge type of MR sensors consisting of 4 single MR sensors made in Si(001)/NiO($300{\AA}$)/NiFe($450{\AA})$ was shown in the range of about ${\leq}{\pm}5$ Oe.

• 한국초전도ㆍ저온공학회논문지
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• 제18권3호
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• pp.10-20
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• 2016

The Cable-In-Conduit-Conductor (CICC) for the ITER tokamak Central Solenoid (CS) has undergone design change since the first prototype conductor sample was tested in 2010. After tests showed that the performance of initial conductor samples degraded rapidly without stabilization, an alternate design with shorter sub-cable twist pitches was tested and discovered to satisfy performance requirements, namely that the minimum current sharing temperature ($T_{cs}$) remained above a given limit under DC bias. With consistent successful performance of ITER CS conductor CICC samples using the alternate design, an attempt is made here to revisit the internal electromagnetic properties of the CICC cable design to identify any correlation with conductor performance. Results of this study suggest that there may be a simple link between the $Nb_3Sn$ CICC internal self-field and its $T_{cs}$ performance. The study also suggests that an optimization process should exist that can further improve the performance of $Nb_3Sn$ based CICC.

• 한국소음진동공학회논문집
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• 제20권12호
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• pp.1200-1209
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• 2010

The main subject of this paper is to develop analytic method with which output power or sensitivity variations of a magnetostrictive ultrasonic transducer can be estimated with no aid of experiments. After the bias magnetic field deployed over the patch is calculated using finite element analysis for magnetostatics, the representative value is extracted by averaging these field values. The operating point on the characteristic curve for magnetostriction is identified by this value and then the output performance is calculated from it. It is verified that the results from this simple model match well with those of its experimental version and some limits of this modeling technique are also considered.