• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.9
• /
• pp.693-699
• /
• 1998

In this work $Cd_4GeS_6:Co^{2+}$(0.5mole%) single crystals were grown by the chemical transporting reactiov(CTR) method using high purity(6N) elements. The grown single crystals crystallized in a monoclinic structure(space group Cc). The direct optical energy gap of this single crystals was found to be 2.445eV at 300K and the temperature dependence of optical energy gap was fitted well to Varshni equation. But at temperatures lower than 70K an anomalous temperature dependence of the optical energy gap was obtained. This anomalous temperature dependence accored well with the anomalous temperature dependence of the unit cell volume. Also, the entropy, enthalpy and heat capacity were deduced from the temperature dependence of optical energy gaps.

• Journal of Magnetics
• /
• v.18 no.3
• /
• pp.225-229
• /
• 2013

We report a measurement for the anomalous Nernst effects induced by a temperature gradient in [CoSiB/Pt] multilayer films with perpendicular magnetic anisotropy. The Nernst voltage shows a characteristic hysteresis which reflects the magnetization of the film as in the case of the anomalous Hall effects. With a local heating geometry, we also measure the dependence of the anomalous Nernst voltage on the distance d from the heating element. It is roughly proportional to $1/d^{1.3}$, which can be conjectured from the expected temperature gradient along the sample from the heat equation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.05a
• /
• pp.167-171
• /
• 2001

High temperature deformation behavior of Fe-28Al-5Cr alloy has been investigated known to show anomalous temperature dependence of yield strength. Specifically, the effect of Cr addition has been examined. A series of tensile and load relaxation tests have been carried out to obtain the flow behavior of Fe-28Al-5Cr alloy at the elevated temperatures. The flow curves have then been analyzed using the inelastic deformation theory recently proposed. Firstly, high temperature flow stress of iron aluminides can be resolved into internal stress and frictional stress. Secondly, the temperature corresponding to peak strength gets higher level at faster strain rate, which presumably due to the increased contribution of internal stress in observed flow stress. And thirdly, the alloying of Cr seems to cause solid-solution strengthening of frictional stress level and the elevation of 2nd order transition temperature. In this analogy, Fe-28Al-5Cr exhibits better strength especially at relatively higher temperature and lower strain rate than Fe-28Al.

• Proceedings of the IEEK Conference
• /
• 2000.06b
• /
• pp.76-79
• /
• 2000

The 3$\mu\textrm{m}$-thick PVDF (Polyvinyiidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR specrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks ate detected at 509.45 and 1273.6〔cm〕 in the FT-IR spectrum, we are confirmed that the ${\beta}$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200Hz to 7000Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy (ΔH) obtained from temperature dependence of dielectric loss is 21.64 ㎉/㏖. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.

• Journal of Information Display
• /
• v.13 no.1
• /
• pp.31-36
• /
• 2012

Ferroelectric liquid crystal parameters, spontaneous polarization, and transition temperature were studied as a function of cell thickness. These parameters were found to increase with increasing cell thickness, but an exception was observed for the transition temperature in the case of a thin cell. A simple Landau model is presented to interpret the theoretical and experimental observations. The anomalous behavior is attributed to the electroclinic effect and is explained using the Landau model.

• Journal of the Korean Magnetics Society
• /
• v.5 no.6
• /
• pp.952-955
• /
• 1995

It is well kown that the side-jump effect, originated from the spin-orbit scatterring of the transport electrons at the site of spin-orbit scatterers, is the reason for the anomalus Hall resistivity which is proportional to the magnetization. Our recent magnetization study implied that abundant ferromagnetic Fe clusters made of for Fe ions dominate the temperature and field dependence of magnetization at high field and low temperature regime for a paramagnetic $Fe_{0.33}Zr_{0.67}$ alloy. We measured the Hall resistivity of this alloy and observed that the Hall resistivity followed the M-H cure at low temperature, and the Hall coefficients at moderate temperatures were proportional to the magnetic susceptibility. We explain the behavior of Hall resistivity with the change of field and temperature in terms of side-jump effect.

• Journal of the Korean Vacuum Society
• /
• v.18 no.6
• /
• pp.426-434
• /
• 2009

A global simulation of $SiH_4/H_2$ discharge is conducted in a planar-type inductively coupled plasma (ICP) discharge. We numerically solve a set of spatially averaged fluid equations for electrons, positive ions, negative ions, neutrals, and radicals. Absorbed power by electrons is determined by an analytic electron heating theory including the anomalous skin effect. Also, we investigate functional dependence of various discharge quantities such as the densities of various species and the temperature of electron on external controllable parameters such as ratio between $SiH_4$ and $H_2$, power and pressure.

• Journal of the Korean Magnetics Society
• /
• v.19 no.4
• /
• pp.121-125
• /
• 2009

Amorphous $Ge_1$_$_xMn_x$ semiconductor thin films grown by low temperature vapor deposition were annealed at various temperatures from 400 to $700^{\circ}C$ for 3 minutes in high vaccum chamber. The electrical and magnetotransport properties of as-grown and annealed samples have been studied. X-ray diffraction patterns analysis revealed that the samples still maintain amorphous state after annealling at $500^{\circ}C$ for 3 minutes and they were crystallized when annealing temperature increase to $600^{\circ}C$. Temperature dependence of resistivity measurement implied that as-grown and annealed $Ge_1$_$_xMn_x$ films have semiconductor characteristics, the increase of resistivity with annealling temperature was obseved. The $700^{\circ}C$-annealed sample exhibited negative magnetoresistance (MR) at low temperatures and the MR ratio was ${\sim}$8.5% at 10 K. The asymmetry was present in all MR curves. The anomalous Hall Effect was also observed at 250 K.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.5
• /
• pp.9-15
• /
• 2000

The 3 ${\mu}{\textrm}{m}$-thick PVDF (polyvinylidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR spectrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks are detected at 509.45 ［$cm^{-1}$ /］ and 1273.6 ［$cm^{-1}$ /］in the FT-IR spectrum, we are confirmed that the $\beta$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200 Hz to 7000 Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy ( $\Delta$H) obtained from temperature dependence of dielectric loss is 21.64 ㎉/mole. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.

• Journal of the Korean Magnetics Society
• /
• v.3 no.1
• /
• pp.7-12
• /
• 1993

The effects of Mn, Cr or Co addItion on the magnetic properties of Fe-Ni Invar alloys were investigated. The composition range of the three additives is up to 5wt%. In the temperature range of room temperature-$250^{\circ}C$, the variation of specific magnetization with the addition of Mn, Cr or Co in the Fe-Ni alloys except for 5wt% Co shows the phenomenon characteristics of the Invar effect, viz., the specific magnetization decreases very abrubtly with the temperature and the dependence of temperature on the specific magnetization is in the mixed form of $T^{3/2}$ and $T^{2}$. In the room temperature, the amount of increase in the specific magnetization, Curie temperature and coercivity is in order of Co > Cr > Mn. In the case of 5wt% Co an anomalous phenomena were observed due to the occurrance of ferromagnetic $\alpha$ phase which reduces the invar effect.