• Journal of Magnetics
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• 제6권2호
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• pp.70-72
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• 2001

We have investigated the activation magnetic moment, which characterizes the basic magnetic moment acting as a single magnetic particle during magnetization reversal. The activation magnetic moment was measured from each local area on continuous ferromagnetic thin films, by analyzing the magnetic field dependence of magnetization reversal of the corresponding local area, based on a thermally activated relaxation process. It was found that the activation magnetic moment was nonuniform on a submicrometer scale; the fluctuation increased with increasing the number of layers in Co/Pd multilayers. The distribution could be well described by exp($\delta m^{3/2}$), where $\delta$m is the deviation of the activation magnetic moment from the mean value.

• 전자공학회논문지A
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• 제28A권10호
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• pp.840-846
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• 1991

In case of the rapid thermal process by halogen lamps, an optical pyrometer is generally used to measure the temperature. It is, however, necessary to measure the temperature by the thermocouple when the process temperature is lower than 700$^{\circ}C$ and the correction of the temperature is required. Contact by the PdAg paste is commonly used out but in this case it is impossible to see the effect of surface states of the substrate, which is critical in the rapid thermal process. In this study, real temperature ramping speed of silicon substrates coveredwith various thin films such as SiO$_2$2, Si$_{3}N_{4}$, dopants, and conductive layers (Ti or Co) was investigated by a mechanical contact of the thermocouple. And the results were compared with the case in which the contact was made by the PdAg paste. Effect of process ambient was also studied. It was found that depending on the surface state, overshoot more than 100$^{\circ}C$ could occur. It was also found that in case of the substrate covered with conductive layers, mechanical contact might render the correct temperature.

• 한국자기학회지
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• 제25권1호
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• pp.1-3
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• 2015

본 연구에서는 스핀-궤도 돌림힘의 광학적 측정 방법을 개발하였다. 사인파 전류에 의해 발생하는 스핀-궤도 돌림힘은 해당 주파수와 두 배 주파수로 진동하는 자화의 운동을 유발하는데, 이로 인해 변화하는 자화의 수직 성분을 극광자기 효과를 이용해 측정하였다. 스핀-궤도 돌림힘이 추가된 란다우-리프쉬츠-길버트 방정식의 평형 조건으로부터, 스핀-궤도 돌림힘에 의한 유효 자기장을 정량적으로 분석하였다. 이러한 측정법을 Pd/Co/Pt 박막 시료에 적용하여, 스핀-궤도 돌림힘 효율의 종 방향과 횡 방향의 성분 값을 각각 나누어 측정하는데 성공하였다. 본 연구에서 제시한 측정 및 분석 방법은 기존의 전기적 측정에 비해 오류가 적기 때문에, 스핀-궤도 돌림힘을 측정하는 더 개선된 방법으로 사용할 수 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2001년도 제21회 학술발표회 초록집
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• pp.92-92
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• 2001

• 한국전기전자재료학회논문지
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• 제29권10호
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• pp.601-607
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• 2016

Piezoelectric thick films of soft $Pb(Zr,Ti)O_3$ (PZT) based commercial material (S55) were fabricated using a conventional tape casting method. Ag-Pd electrodes were printed on the piezoelectric film at room temperature and all 5 layered films with a dimension of $12mm{\times}16mm$ were successfully laminated for a multi-layered piezoelectric ceramic actuator. The laminated specimens were co-fired at $1,100^{\circ}C$ for 1 h. A flat layered and dense microstructure was obtained for the $112{\mu}m$ thick piezoelectric actuator after sintering process. Thereafter, a prototype piezoelectric speaker was fabricated using the multi-layered piezoelectric ceramic actuator which can operate as a bimorph. Its SPL (sound pressure level) characteristic was also evaluated for speaker application. Frequency response revealed that the output SPL with a root mean square voltage of 10 V increased gradually to the highest peak of 87.5 dB for 1.5 kHz and exhibited a relatively stable behavior over the measured frequency range (${\leq}20kHz$) at a distance of 10 cm, implying that the fabricated piezoelectric speaker is potential for speaker applications.

• 한국자기학회지
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• 제2권3호
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• pp.263-267
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• 1992

토크마그네토미터를 이용하여 일축이방성이 있는 자성체의 자화와 인가자장의 방향에 따른 보자력을 정확하게 측정하는 새로운 방법을 개발하였다. 자화와 보자력을 측정하기 위해 시편을 자화용이축 방향으로 포화시킨 후, 자화용이축과 이루는 자장의 각도$({\phi})$ 가 $1/2{\pi}$와 ${\pi}+{\delta}$에서 자장(H)를 증가시켜 가며 자장의 변화에 따른 토크$({\tau})$ 곡선들을 얻었다. 자화는 ${\phi}$가 $1/2{\pi}$인 토크곡선에서 ${\tau}/H$를 측정하여 얻을 수 있었고 보자력은 ${\phi}$가 ${\pi}+{\delta}$인 토크곡선에서 ${\tau}$ = 0 이 되는 자장의 세기로부터 구할 수 있었다. 기존의 VSM에 의한 측정과 비교한 결과 2 % 이내에서 일치함을 보였으며, 토크마그네토미터의 고감도로 인해 VSM에 의한 방법보다 정밀한 자화 측정이 가능하였다.

• 한국군사과학기술학회지
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• 제7권2호
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• pp.81-87
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• 2004

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets. 1) The Pt or Pd $(1,\;2,\;3\;wt.\%)$ as catalyst is impregnated in the base material of $SnO_2$ by impregnation method.2) $Al_2O_3\;(0,\;4,\;12,\;20\;wt.\%),\;In_2O_3\;(1,\;2,\;3\;wt.\%),\;WO_3\;(1,\;2,\;3\;wt.\%),\;TiO_2\;(3,\;5,\;10\;wt.\%)$ or $SiO_2\;(3,\;5,\;10\;wt.\%)$ is added to $SnO_2$ by physical ball milling process. 3) ZnO $(1,\;2,\;3,\;4,\;5\;wt.\%)$ or $ZrO_2\;(1,\;3,\;5\;wt.\%)$ is added to $SnO_2$ by co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by the SEM, XRD and BET respectively. Response characteristics are examined for simulant gases with temperature in the range 200 to $400^{\circ}C$, with different gas concentrations. These sensors have high sensitivities more than $50\%$ at 500ppb concentration for test gases and also have shown good repetition tests. Four sensing materials are selected with good sensitivity and stability and are fabricated as a sensor array A sensor array Identities among the four simulant gases through the principal component analysis (PCA). High sensitivity is acquired by using the semiconductor thick film gas sensors and four CWA gases are classified by using a sensor array through PCA.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.581-588
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• 2016

Piezoelectric thick films of a soft $Pb(Zr,Ti)O_3$ (PZT) based commercial material were produced by a conventional tape casting method. Thereafter, the interdigitated (IDT) Ag-Pd electrode pattern was printed on the $25{\mu}m$ thick piezoelectric film at room temperature. Co-firing of the 10-layer laminated piezoelectric thick films was conducted at $1,100^{\circ}C$ and $1,150^{\circ}C$ for 1 h, respectively. Piezoelectric cantilever energy harvesters were successfully fabricated using the IDT electrode pattern embedded piezoelectric laminates for 3-3 operation mode. Their energy harvesting characteristics were investigated with an excitation of 120 Hz and 1 g under various resistive loads (ranging from $10k{\Omega}$ to $200k{\Omega}$). A parabolic increase of voltage and a linear decrease of current were shown with an increase of resistive load for all the energy harvesters. In particular, a high output power of 3.64 mW at $100k{\Omega}$ was obtained from the energy harvester (sintered at $1,150^{\circ}C$).