• 한국재료학회지
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• 제3권4호
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• pp.422-423
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• 1993

이 short note에서 우리는 bulk gadolinium의 강자성에서 상자성으로의 전이온도(즉, Curie점) 측정에 대한 결과를 보고하고자 한다. 이 결과보고는 gadolinium박막에 대한 이전의 결과에 정당성을 주기 위해서 쓰여졌다. 본 실험에서 bulk gadolinium의 Curie점은 시료의 저항을 온도의 함수로 측정함으로써 결정하였다. 이는 Curie점에서 비열의 특이성이 바로 비저항의 특이성으로 연결되기 때문이다. 결과적으로 우리는 bulk gadolinium의 Curie점이 19.2${\pm}$0.$3^{\circ}C$가 되고이 값은 비열의 실험치로 결정한 다른 그룹들의 실험값들과 잘 일치하고 있음을 알 수 있었다.

• Journal of Magnetics
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• 제1권2호
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• pp.86-89
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• 1996

The dc magnetron sputter deposited (Pt/Co/Pt/Ni) multilayers which exhibited Curie temperatures in the range of 150-$300^{\circ}C$ were studied as possible alternative multilayers for magneto-optical recording to the widely studied Co/Pt, whose Curie temperatures are in the range of 200~$400^{\circ}C$. The Coercivities of these multilayers were between 450 Oe and 800 Oe. These multilayers exhibited comparable magnetic and magneto-optical properties to Co/Pt multilayers with enhancement of the Kerr rotation at lower wavelengths and negligible Kerr ellipticity over a wide range of the spectrum (4000~7000$\AA$ ).

• Journal of Korean Vacuum Science & Technology
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• 제1권1호
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• pp.13-18
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• 1997

The critical phenomena in nickel films have been studied by observing the resistivity behavior with temperatures near the Curie point. We observed the thickness dependence of the Curie point in nickel films, that is, the thinner the film is, the lower the Curie point is. This is as expected. Using the heat capacity data, we also found the amplitude ratios of bulk and film systems to be 1.222 and 1.197(average0, respectively. These values are cose to the theoretical prediction of 1.46 given by the Heisenberg, S=$\infty$ Model.

• 한국결정성장학회지
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• 제1권1호
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• pp.1-4
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• 1991

The applicability of $LiNbO_{3}$ as a substrate for fabrication of Ti-indiffused waveguide electro-optic devices is limited. Ti diffuses comparatively in congruently melting $LiNbO_{3}$; the Curie temperature of this material is too low to permit diffusion temperatures much above $1100^{\circ}C$ without the necessity of re-poling the crystal. Both of hese difficulties could be eliminated by incorporating certain dopants in $LiNbO_{3}$. Crystals of $LiNbO_{3}$ doped with Ti and Mg were grown and evaluated. The electroptic coefficients and birefringence of $LiNbO_{3}$ doped crystals were measured at ${\lambda}=.6328$ and $1.32\;$\mu{m}$. Curie temperatures were measured. The Curie temperature of both undoped and Ti-doped $LiNbO_{3}$ was $1130^{\circ}C$; that for Mg-doped $LiNbO_{3}$ was $30^{\circ}$ higher. From these data, a composition for the crystals was estimated. Thermogravimetric data confirmed this estimate and showed that the composition of Mg : $LiNbO_{3}$ was $49.3{\pm}0.2mole%\;Li_{2}O$ ; the composition of the undoped and Ti : $LiNbO_{3}$ samples was $48.6{\pm}0.2mole%$. Diffusion of Ti into both Mg-doped and Ti-doped $LiNbO_{3}$ crystals was studied as a function of $Li/NbO_{3}$ ratio and temperature.

• Applied Science and Convergence Technology
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• 제26권5호
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• pp.143-147
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• 2017

Structural studies on the addition characteristics of Nb ions to $BaTiO_3$ solid solutions were performed by XRD and SEM/EDS technique. The X-ray diffraction peaks of the (111), (200) and (002) planes of Nb-doped $BaTiO_3$ solid solutions with different mole% of Nb were analyzed. We also investigated the relationship between the dielectric and structural properties of Nb-doped $BaTiO_3$. The transition temperatures of $BaTiO_3$ solid solution doped with 0.5mole%Nb and 1.0 mole%Nb were ${\sim}116^{\circ}C$ and ${\sim}87^{\circ}C$, respectively, which were found to be shifted to very low temperature from the transition temperature of pure $BaTiO_3$ (about $125^{\circ}C$). As a result of analysis of 1/K versus T and ln[$(1/K)-(1/K_m)$ versus ($T-T_m$)] of the two compositions used in this experiment, the diffusivity slightly differs from that of pure $BaTiO_3$ at temperatures above Curie temperature. And this characteristic was analyzed by applying the modified Curie-Weiss law.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.220-223
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• 1987

In this paper, electro-optic characteristics of PLZT 7.6/70/30 composition in MPB regions, which antiferroelectric and ferroelectric phases coexist together, were studied. As sintering times are increased, Curie temperatures ore linearly decreased. And the antiferroelectric phase becomes more stronger when Curie temperatures are decreased. The crystal structure investigated by lie of X-ray analysis is proved to cubic in the thermally depoled specimen and rhombohedral in the poled specimen. Accordingly, the applicability of 7.6/70/30 specimen as image storage and display device is expected by the method for applying field induced reversible transitions between antiferroelectric(AFE) and ferroelectric(FE) phase.

• Bulletin of the Korean Chemical Society
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• 제30권6호
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• pp.1267-1273
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• 2009

The correlation between the sintering temperature and dielectric properties in the $Nb^{5+}\;and\;Ta^{5+}$ doped BaTi$O_3$ solid solutions have been investigated. The samples were sintered at temperatures ranging from 1250 to 1350 ${^{\circ}C}$ for 4 h in air. SEM, XRD and SEM/EDS techniques were used to examine the structure of the samples with particular focus on the incorporation of $Nb^{5+}\;and\;Ta^{5+}$ ions into the BaTi$O_3$ crystal lattice. The X-ray diffraction peaks of (111), (200) and (002) planes of BaTi$O_3$ solid solution doped with different fractions of $Nb^{5+}\;and\;Ta^{5+}$ were investigated. The dielectric properties were analyzed and the relationship between the properties and structure of doped BaTi$O_3$ was established. The fine-grain and high density of the doped BaTi$O_3$ ceramics resulted in excellent dielectric properties. The dielectric properties of this solid solutions were improved by adding a small amount of dopants. The transition temperature of the 1.0 mole% $Ta^{5+}$ doped BaTi$O_3$ solid solution was $\sim$110 ${^{\circ}C}$ with a dielectric constant of 3000 at room temperature. At temperatures above the Curie temperatures, the dielectric constant followed the Curie-Weiss law.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권1호
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• pp.1-5
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• 2001

P(VDF/TrFE) copolymer thin films with 70/30 and 80/20 mol% VDF (polyvinylidene fluoride) and TrFE (trifluoroethylene) rates were prepared by using a vapor deposition method, During thin films were prepared, the substrate temperatures were maintained at 30 $^{\circ}C$ and 120 $^{\circ}C$, and the heating source temperature was fixed at 350 $^{\circ}C$. Contary to PVDF homopolymer, P(VDF/TrFE) copolymers showed the Curie point(Tc) below the melting point. The Curie point (Tc) and the melting point of the P(VDF/TrFE) copolymers were changed as a function of substrate temperature and the VDF mol%. The Curie point and the melting point of P(VDF/TreFE) thin films decreased and increased with increasing substrate temperature, respectively. Also with increasing VDF mol%, the melting point decreased slightly, however the Curie point increased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.8-12
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• 1994

Solid solutions $Sr_2$($Ta_{1-x}$$Nb_{x}$)$_2$$O_{7}$ (x = 0.0 - 1.0) composed of strontium-tantalate (low Curie temperature) and strontium-niobate (high Curie temperature) were prepared by the conventional mixed oxide method and the molten salt synthesis method (flux method). Phase relation, sintering temperature, grain-orientation and dielectric properties were investigated for sintered ceramic samples with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. Single phase $Sr_2$$Nb_2$$O_{7}$ powder was synthesized by using flux method at lower temperatures, and sintering temperature was also reduced by using flux method derived powder than using mixed-oxide derived powder. Sintering characteristics and dielectric properties of specimens prepared by flux method were better than those derived through the conventional method.

• 한국재료학회지
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• 제26권1호
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• pp.35-41
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• 2016

The electrical transport properties of $La_{0.5}Sr_{0.5}CrO_3$ below room temperatures were investigated by dielectric, dc resistivity, magnetic properties and thermoelectric power. Below $T_c$, $La_{0.5}Sr_{0.5}CrO_3$ contains a dielectric relaxation process in the tangent loss and electric modulus. The $La_{0.5}Sr_{0.5}CrO_3$ involves the transition from high temperature thermal activated conduction process to low temperature one. The transition temperature corresponds well to the Curie point. The relaxation mechanism has been discussed in the frame of electric modulus spectra. The scaling behavior of the modulus suggests that the relaxation mechanism describes the same mechanism at various temperatures. The low temperature conduction and relaxation takes place in the ferromagnetic phase. The ferromagnetic state in $La_{0.5}Sr_{0.5}CrO_3$ indicates that the electron - magnon interaction occurs, and drives the carriers towards localization in tandem with the electron - lattice interaction even at temperature above the Curie temperature.