• Journal of Magnetics
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• 제10권4호
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• pp.157-162
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• 2005

We report the magnetic-field dependence of the irreversible magnetization of binary superconductor $MgB_2$. For the temperature region of $T\;<\;0.9T_c$, the contribution of the bulk pinning to the magnetization overwhelms that of the surface pinning. This was evident from the fact that the magnetization curves, M(H), were well described by the critical-state model without considering the reversible magnetization and the surface pinning effect. It was also found that the M(H) curves at various temperatures scaled when the field and the magnetization were normalized by the characteristic caling factors H$\ast$(T) and M$\ast$(T), respectively. This feature suggests that the pinning mechanism determining the hysteresis in M(H) is unique below $T\;=\;T_c$.

• 한국자기학회지
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• 제23권5호
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• pp.154-158
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• 2013

자성-금속-자성 삼층구조로 반강자성 결합 특성을 갖는 박막 재료의 자화 곡선은 두 자성박막 각각의 자화량($M_1$, $M_2$) 변화 특성을 반영한다. 본 연구에서는 반강자성 결합 특성을 갖는 CoB/Ru/CoB 박막 재료의 두 자성 박막의 총자화량($M_{tot}=M_1+M_2$)과 상부 단일 박막의 자화량($M_1$)의 이론적 값을 Stoner-Wohlfarth 모델로 계산하였다. VSM으로 측정한 총자화량은 자기장의 반전에 따라 가역 특성을 보였으며, CoB/Ru/CoB 재료의 플롭자기장($H_F$)은 약 50 Oe였다. 한편 MOKE로 측정한 상부 단일 박막의 자화량($M_1$)은 $-H_F$ < H < $H_F$에서 비가역 자화 반전 특성을 보였다. 이러한 자화 거동 특성은 두 자성 박막에 서로 상호 작용하는 반강자성 결합에 의하여 두 자성 박막 각각의 자화 각도 변화에 기인함을 Stoner-Wohlfarth 모델 계산을 통하여 확인하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2005년도 하계학술연구발표회 논문개요집
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• pp.34-35
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• 2005

• Journal of Magnetics
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• 제17권3호
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• pp.168-171
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• 2012

Irreversible magnetization between the zero-field-cooled (ZFC) and field-cooled (FC) states in $Y_{1-x}Sr_xMnO_3$ (x=0 and 0.2) was investigated. $YMnO_3$ and $Y_{0.8}Sr_{0.2}MnO_3$ have a hexagonal structure and the lattice parameter a decreases from 7.4408 ${\AA}$ to 7.4327 ${\AA}$ while c increases from 12.2244 ${\AA}$ to 12.2287 ${\AA}$ for $YMnO_3$ and $Y_{0.8}Sr_{0.2}MnO_3$, respectively. An anomaly is observed at around 74 K in ZFC and FC magnetization measurements for $YMnO_3$, whereas in $Y_{0.8}Sr_{0.2}MnO_3$ the ${\sigma}_{ZFC}$ and ${\sigma}_{FC}$ are split at low temperature, indicating glass-like behavior.

• Journal of Magnetics
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• 제4권1호
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• pp.13-16
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• 1999

Magnetic viscosities of a commercialized metal evaporated tape were measured as a function of sweeping rate in VSM at room temperature. Within several seconds in the viscosity measurement, curves are downward concave and more concave with increasing sweeping rate when magnetization were plotted as a logarithmic function of time. However, magnetization varied as a logarithmic function of time after several seconds. Magetic viscosity coefficient gradually increased with increasing sweeping rate and then kept a constant value at a rate faster than 61.5 Oe/s. It was supposed that magnetic viscosity occurs during field sweeping, which was in good agreement with Sharrock's model qualitatively. Activation volume decreased with increasing sweeping rate, which was due to the fact that magnetic viscosity coefficients increased with sweeping rate while irreversible susceptibilities were not affected by sweeping rate.

• 전자공학회논문지A
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• 제29A권4호
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• pp.22-27
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• 1992

The cyclic voltammogram characteristics at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics/(($10^{-3}$M KCI + p-Si powders) and /(($10^{-4}$M CsNO$_3$ + n-GaAs powders) suspension interfaces have been studied using the microelectrophoresis and the cyclic voltammetric method. The negatively charged ions are specifically absorbed on the virgin and the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics surfaces. The zeta potentials of the p-Si and n-GaAs colloidal semiconductors are + 41mV and -44.8mV, respectively. The magnetization effects act as potential barriers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The positivelely charged p-Si and the negatively charged n-GaAs colloidal semiconductors act as potential barriers at the virgin SrO${\cdot}6Fe_{2}O_{3}$ interfaces. On the other hand, the charged p-Si and n-GaAs colloidal semiconductors act as potential barrier scavengers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The magnetization effects and the charged colloidal semiconductor effects are irreversible and interdependent.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.121-124
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• 2000

The time dependence of irreversible magnetization of grain aligned infinite layer superconductor Sr$_{0.9}$La$_{0.1}$CuO$_2$ was measured in temperature range of 2 K < T < 30 K for H= 0.5 T, 1.0 T and 1.5 T parallel to c-axis. From this, we calculated normalized flux creep rate S(T) ${\equiv}$ dlnM/dlnt and found that the temperature independent region in S(T) is significantly wide in comparision with other cuprate superconductors. Using the method of Maley et al., we also deduce the current density dependence of pinning potential and glassy exponent ${\mu}$.

• 한국소음진동공학회논문집
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• 제20권9호
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• pp.841-848
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• 2010

Previous experimental results show that the magnetostrictive transducer has the peculiar characteristic with relation to their reversible magnetization and its practical usage will be hindered by this phenomena. In this paper, the idea of anhysteretization is adopted in order to solve this problem. The experimental results reveal that the anhysteretization can get rid of the extraordinary phenomena which are occurred by the change of biasing magnetic field. The effects of two important parameters, which are the amplitude and the decaying time of this process, on the anhysteretization are investigated experimentally. Finally the best operating condition is proposed in order to maximize the sensitivity under the anhysteretization.

• 한국초전도ㆍ저온공학회논문지
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• 제24권3호
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• pp.41-46
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• 2022

The superconducting properties of high temperature superconducting (HTS) GdBCO coated conductor (CC) tape (Ag/GdBCO/Buffer-layers/Stainless Steel) were investigated, specifically a series of samples prepared by vacuum heat treatment (200℃ to 600℃), using a Quantum Design PPMS-14. The critical current density J_c value was obtained by applying the modified Bean model to the irreversible magnetization ∆M_irr(H) data which was estimated from the magnetization M(H) loop. The reduction rates of lnJ_c and T_c values according to the increase of the vacuum annealing temperature T_an were d(lnJ_c)/dT_an = - 0.016 A/(cm²∙℃) and dT_c/dT_an = - 0.24, respectively. We examined the effect of recovery temperature T_re (475℃ to 700℃) and recovery duration time t (0.5 h to 24 h) on the restoration of previously completely lost superconductivity in samples that subsequently received heat treatment in an O₂ gas flow space. All samples were fully restored to superconductivity by heat treatment in an O₂ gas flow space. The recovery temperatures T_re (475℃ to 700℃) and recovery duration times t (0.5 h to 24 h) were both independent of the superconductivity recovery characteristics.

• 대한화학회지
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• 제37권10호
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• pp.895-902
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• 1993

란탄나이드 3가($Pr^{3+}$ 와 $Dy^{3+}$)와 유기 리간드를 (phen', terpy') 착물들의 거동을 UV/vis 분광분석, 자기화 그리고 전기화학적 방법에 의해 조사하였다. 착물들의 결정장 갈라짐 에너지 크기와 짝지움에너지 그리고 스핀상태는 착물들의 스펙트라로부터 얻었다. 이들 착물들에 대한 전지화학적 거동은 비수용매속에서 순환 전압전류법에 의해 관찰하였다. 이들 환원피크는 전자 전이에 의한 비가역적인 2단계의 환원 과정이었다.