• Journal of the Optical Society of Korea
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• v.17 no.3
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• pp.279-282
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• 2013

This work presents a theoretical study on the analytical calculation of the lineshape of polarization spectroscopy (PS) for the transition line $5s^2\;^1S_0{\rightarrow}5s5p\;^1P_1$ of $^{88}Sr$. From the obtained analytical form of the PS spectrum, we were able to identify how the saturation affected the lineshape of the PS spectrum. The results obtained will be useful for polarization spectroscopy experiments using the alkaline-earth atoms such as Sr or Yb.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.247-250
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• 1991

In this paper, we have investigated the poling conditons depending upon the electric field and temperature for PZT ceramics with various stoichiometry prepared by wet direct method, and $MnO_2$ dopant. The electric field required for saturation polarization was plotted against temperature $(1,000/T^{\circ}K)$ so that the required field could be estimated at any given temperature by measuring the charge displaced during poling. From this curve it should be possible to predict the field required to produce maximum domain switching at temperature below the Curie temperature, when $MnO_2$ dopant was added to the PZT ceramics, the electric field required for saturation polarization was lowered than that of undoped PZT samples.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.613-616
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• 2002

The polarization properties of $BaTiO_3$ were investigated by using thermally stimulated depolarization current (TSDC) technique. Two peaks were observed at about 400 K (peak A) and 435 K (peak B) from TSDC spectra obtained from the temperature range of 280-500 K. Peak A shows a sharp decrease of TSDC due to extinction of spontaneous polarization above the phase transition temperature of $BaTiO_3$. The values of activation energy of peak A and peak B were calculated to be 0.70 eV and 0.87 eV respectively. From the results of TSDC measurement with a variation of polarizing electric field strength, we found that saturation of total current of TSDC was started from 3kV/cm. However, the amount of total current of TSDC was not affected by the variation of polarizing time.

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.3
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• pp.81-86
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• 2019

Overhauser dynamic nuclear polarization (O-DNP) has been an efficient method to boost the thermal nuclear polarization in liquids at room temperature. However, O-DNP for a benchtop NMR using a permanent magnet has remained unexplored yet. In this work, we report the development of an O-DNP system adopting a permanent magnet of 1.6 T. Q-band (~43 GHz) high-power amplifier produced 6 W microwave for saturation. Instead of resonator, we used an open-type antenna for the microwave irradiation. For several representative small molecules, we measured the concentration and frequency dependences of the enhancement factor. This work paves the way for the development of a benchtop DNP-NMR system overcoming its disadvantage of low quality signal when using a permanent magnet.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.891-896
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• 1998

The relaxation and elimination characteristics of polarization-photoinduced dichroism have been investigated in amorphous chalcogenide thin films deposited having normal(0。) and obique (80。) vapor incident angles. The dark relaxation kinetics of dichroism from a saturation point(D\ulcorner\ulcorner) to a certain relaxation point(D\ulcorner\ulcorner) grew to be longer on subsequent cycles of switching on and off of the inducing light, and these decays are changed from simple exponential decay to stretched exponential decay. The dichroism induced by a long time(~3.3 hrs) exposure exhibited the characteristics of longer time maintenance and smaller decreasing rate, in contrast with that by a short time (~min) exposure. In addition, the dichroism was eliminated by the exposure of non-polarized He-Ne laser.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.166-173
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• 2001

Hysteresis loops of the ferroelectric thin films such as PLZT(10/30/70), PLT(10) and PZT(30/70) was simulated using the field-dependent polarization model and compared to the measured loops. In case of PZT(30/70) thin film, as the real saturation or polarization at the applied voltage or larger than 5V appears slack and its value is quite different from the simulated one, it is deduced that the ferroelectric polarization of PZT(30/70) is generated not only by the pure dipoles but also by various electric charges. The drain current of quasi-MFISFET is expressed by using the square-law FET and field-dependent polarization models. The modeling results are analogous to the experimental values. The channel of quasi-MFISFET using PZT(30/70) forms more quickly compared to that of quasi-MFISFET using PLZT(10/30/70) or PLT(10) in the state of 'write' gate voltage of -10V. This may be because the decrease rate of the polarization in the PZT(30/70) thin film is 3~4 times more rapid than that of the polarization in the PLZT(10/30/70) or the PLT(10) thin film in the retention characteristics.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.1
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• pp.1-10
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• 2003

Device characteristics of the Metal-Ferroclecric-Semiconductor FET(MFSFET) are simulated in this study. The field-dependent polarization model and the square-law FET model are employed in our simulation. C-V$_{G}$ curves generated from our MFSFET simulation exhibit the accumulation, the depletion and the inversion regions clearly. The capacitance, the subthreshold and the drain current characteristics as a function of gate bias exhibit the memory windows are 1 and 2 V, when the coercive voltages of ferroelectric are 0.5 and 1 V respectively. I$_{D}$-V$_{D}$ curves are composed of the triode and the saturation regions. The difference of saturation drain currents of the MFSFET device at the dual threshold voltages in I$_{D}$-V$_{D}$ curve is 1.5, 2.7, 4.0, and 5.7 ㎃, when the gate biases are 0, 0.1, 0.2 and 0.3V respectively. As the drain current is demonstrated after time delay, PLZT(10/30/70) thin film shows excellent reliability as well as the decrease of saturation current is about 18 % after 10 years. Our simulation model is expected to be very useful in the estimation of the behaviour of MFSFET devices.T devices.

• Journal of Magnetics
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• v.14 no.3
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.

• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.42-45
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• 2002

Properties of lead zirconate titanate ferroelectric thin films prepared by rapid thermal annealing/direct insertion thermal annealing were investigated. The remnant polarization (Pr), saturation polarization (Ps), and coercive force (Ec) of typical samples annealed by rapid thermal annealing (RTA) are about 13.7 $\mu$ C/cm$^2$, 27.1 $\mu$C/cm$^2$, and 55.6 kV/cm, respectively. The dielectric constant of the sample is about 786, the dielectric loss tangent is about 2.4% at 1 kHz. Furthermore, ferroelectric, conduction, and piezoelectric properties of the thin films annealed by RTA process and the direct insertion thermal annealing (DITA) process were compared. The influence of temperature in the dry process on the above properties was also investigated.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.76-83
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• 1999

Fracture toughness({TEX}$J_{IC}${/TEX}) on 304 austenitic stainless steel weldments artificially degraded for long period under SCC environments were evaluated to investigate its reliability and environmental characteristics. Electro-chemical polarization tests were previously carried out to evaluate corrosion susceptiblility of weldment, and stress corrosion cracking was tested under various conditions of 3.5wt.% NaCl solution, the temperature of $25^{\circ}$C and $95^{\circ}$C, and oxygen concentration during 3000hours. From the results obtained, it was found that 304 stainless steel weldment was so susceptible under high temperature and high oxygen concentration of 3.5wt.% NaCl solution, and fracture toughness({TEX}$J_{IC}${/TEX}) was also considerably reduced by material degradation.