• Title, Summary, Keyword: Curie temperature

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Tunable Dielectric Properties and Curie Temperature with BST Thick Films (BST 후막의 가변 유전특성과 큐리온도에 관한 연구)

  • Kim In-Sung;Song Jae-Sung;Min Bok-Ki;Jeon So-Hyun
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.8
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    • pp.392-398
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    • 2006
  • The properties of tunable dielectric materials on RF frequency band are important high tunability and low loss for RF variable devices, variable capacitor, phased array antenna and other components application. Various composite of BST(barium strontium titanate) ratio combined with other non-electrical active oxide ceramics have been formulated for such uses. We present the tunable properties and Curie temperature on BST thick films. The grain growth of the weight ratio of $BaTiO_3$ increased. This can be explained by the substitute $Sr^{2+}$ ion for $Ba^{2+}$ ion in the $BaTiO_3$ system. The Curie temperature was shifted to lower temperature with increasing $SrTiO_3$in the $BaTiO_3-SrTiO_3$ system, because of decreasing the lattice constant. Also, the dielectric constant, tunability and K-factor of $(Ba_xSr_{1-x})TiO_3$ at over the Curie temperature decreased, at over the $60^{\circ}C$ fixation, maximum dielectric constant at Curie temperature and hence sharper phase transformation occurred at Curie temperature. The result were interpreted as a process of internal stress relaxation resulting form the increase of $90^{\circ}$ domains induced the BST. As a result, It is concluded that over the Curie temperature, frequency response and DC field effect for the tunable properties of BST thick film are suppressed by the transition broadening. For the application of tunable devices, that the curie temperature was investigated to be increased.

The study on controling curie temperature for the temperature-sensitive Magnetic materical at colling method. (냉각방법에 의한 감온자성체의 큐리온도 조정에 관한 연구)

  • Bae, Jin-Ho;Sin, Yong-Cheol;Kim, Han-Geun
    • Proceedings of the KIEE Conference
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    • pp.828-830
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    • 1988
  • This paper considered temperature-sensitive characteristics on the basis of curie tempeature and quenching method in the process of manufacturing Mn-Cu-Zn Fersite. The results are as follow. Curie tempeature drops according as the content of CuO and ZnO increases. It also decreases according as sintering temperature increases when the content of ZnO in fixed. Curie temperature drops more in quenching than in slow cooling and activation energy diminishes were too. On the basis of curie tempeature, activation energy is greater in paramagnetic region than in ferrimagnetic region. As its voltage-crrent characteristics is similar to that semiconductors, the temperature-sensitive ferrite is expeated to be appied in the area of power electronics.

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Curie Temperature and Tunable Dielectric Properties of Barium Strontium Titanate Thick Films (티탄산 바륨 스트론튬 (BaxSr1-xTiO3) 후막의 상전이온도와 가변 유전특성)

  • Jeon, So-Hyun;Kim, In-Sung;Min, Bok-Ki;Song, Jae-Sung;Yoon, Jon-Do
    • Journal of the Korean Ceramic Society
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    • v.43 no.7
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    • pp.421-426
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    • 2006
  • [ $(BaSr)TiO_3$ ] thick films were prepared by tape casting method, using $BaTiO_3\;and\;SrTiO_3$ powder slurry in order to investigate dielectric properties i.e. dielectric constant, ${\varepsilon}_r$, Curie temperature, $T_c$. Grain growth within $(BaSr)TiO_3$ thick films was observed with increasing weight ratio of $BaTiO_3$. This observation can be explained by phenomena of substitution of $Sr^{2+}$ ion for $Bi^{2+}$ ion in the $BaTiO_3$ system. Also, the Curie temperature in $(BaSr)TiO_3$ thick films was shifted to lower temperature range with increasing $ SrTiO_3$. Furthermore, Curie temperature having maximum dielectric constant was in the range of $-40^{\circ}C\;to\;30^{\circ}C$, and hence sharper phase transformation occurred at Curie temperature. There occurred decrease in tunability and k-factor of $(Ba_{0.6}Sr_{0.4})TiO_3$ calculated from the dielectric constant, ${\varepsilon}_r$ above Curie temperature. In addition, above the $60^{\circ}C$, phase fixation was observed. This means that internal stress relief occurred with increasing $90^{\circ}$ domains.

Variation of the Curie Temperature in $BaTiO_3$ Doping $Cd_5(PO_4)_3Cl$ ($BaTiO_3$에서 $Cd_5(PO_4)_3Cl$의 첨가로 인한 Curie 온도변화)

  • Kim, Gwang-Chul
    • Journal of the Semiconductor & Display Technology
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    • v.10 no.1
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    • pp.95-99
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    • 2011
  • $(1-x)BaTiO_3+(x)Cd_5(PO_4)_3Cl$ ceramics were prepared by the conventional ceramic technique, i.e., solid state reaction at high temperature. The concentration of $Cd_5(PO_4)_3C$ was varied from 0.01 to 0.15 mole fraction. In order to study the phase transitions of our ceramics, the Raman scattering spectra were measured as functions of concentration x and temperature. It was found that the soluble limit of $Cd_5(PO_4)_3Cl$ in $BaTiO_3$ was the x=0.05 composition and $BaTiO_3$ phase disappeared above x=0.10. A new phase identified as $Ba_4Ti_3P_2O_{15}$ was detected in all samples of our compositions. The Curie temperature shifts up to $130^{\circ}C$ as the concentration x increases from zero to 0.05 and shift down to $95^{\circ}C$ as further increases to 0.08. For the increase of the Curie temperature, it is suggested that it can result from the inhibition of displacement of $Ti^{4+}$ in the distorted octahedron due to well dispersed $Ba_4Ti_3P_2O_{15}$ and $Cd_5(PO_4)_3Cl$ phase.

Curie Temperature Shift in Gadolinium Films due to Finite-Size Effects (유한 효과에 의한 Gadolinium 박막의 Curie온도 이동)

  • Rhee, Il-Su;Chu, Gyo-Jin;Lee, Eui-Wan;Lee, Sang-Yun;Lee, Chong-Yong;Kim, Yaung-Soo;Kim, Dong-Lak;Ri, H.C.
    • Korean Journal of Materials Research
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    • v.4 no.6
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    • pp.710-714
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    • 1994
  • We determine the Curie temperature of thin gadolinium films by the measurement of magnetization as a function of temperature. From these data, we observe the Curie temperature shift in films from the bulk value, and also see the systematic behavior of this shift with thicknesses of films, that is, the larger the shift is, the thinner the film is. In this paper, we analyze and explain these results in light of finite-size scaling theory.

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Electrical Transport and Magnetic Properties in ${(LaMn) }_{1-λ }O }_{3 }$ (${(LaMn) }_{1-λ }O }_{3 }$의 전기전도 및 자기적 특성)

  • 정우환
    • Journal of the Korean Ceramic Society
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    • v.35 no.8
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    • pp.885-889
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    • 1998
  • The temperature dependence of dc conductivity and magnetic properties of cation deficient {{{{ { {(LaMn) }_{1-λ }O }_{3 } }} systems has been investigated,. Above 160K the magnetic susceptibility of all samples followed the Curie-Weiss law. The Curie temperature decreased as the cation deficiency increased. This is due to a strong Jahn-Teller effect originated from electrons of {{{{ { Mn}^{3+ } }} In the case of samples annealed in air and oxygen at-mosphere the charge carriers responsible for conduction in the ferromagnetic regime below the Curie tem-perature are believed to have both magnetic and lattice characteristics. However the conduction carriers in the paramagnetic regime above the Curie temperature are though to be formed by hopping process of small polarons which were generated by assistance of the Jahn-Teller effect.

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Magnetic Properties of FeCoSiB Amorphous Films Annealed in Magnetic field (자계중 열처리된 FeCoSiB 아몰퍼스박막의 자기적 특성)

  • 신광호;김영학;사공건
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.12S
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    • pp.1305-1309
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    • 2003
  • To utilize FeCoSiB amorphous films for magnetoelastic sensors, the temperature dependency of magnetization (M-T curve) and the magnetization properties of the amorphous films were investigated in this study. As the amount of cobalt In the films increased, the Curie temperature decreased but the crystallization temperature increased. In addition to this, the crystallization temperature was lower than the Curie temperature in the film containing 20 at% cobalt. The optimized annealing condition was set up by analyzing the H-T curve. And then, the amorphous film that has excellent magnetic properties and uni-axal anisotropy could be prepared for construction of the magnetoelastic sensor devices. The coercive force of the film was below 0.5 Oe and the anisotripic field was about 5 Oe.

The Determination of Curie Point of Bulk Gadolinium (Bulk Gadolinium의 Curie점 결정)

  • Lee, Il-Su;Lee, Ui-Wan;Lee, Sang-Yun
    • Korean Journal of Materials Research
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    • v.3 no.4
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    • pp.422-423
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    • 1993
  • In this short note, we report the result of measurement for the ferro- to paramagnetic phase transition temperature, that is Curie point of bulk gadolinium. This note is written to give the solid validity for the previous measurement of Curie point shift of gadolinium film (1. Rhee, E. Lee and S. Lee, Kor. J. of Mat. Research,3, 3, 1993). The Curie point of bulk gadolinium is determined by measuring the resistance of sample as function of temperatures. At Curie point, we can observe the resistivity anomaly which arises due to the heat capacity difference between below and above Curie point. Finally, the curie point of bulk gadolinium is found to be 19.2${\pm}$0.$3^{\circ}C$.

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Magnetic Susceptibility of the Single Crystal MnF2(1.5% EuF3) (단결정 MnF2(1.5% EuF3)의 자기 감수율)

  • Lee, Jun-Young;Nahm, Kyun;Kim, Chul-Koo
    • Journal of the Korean Magnetics Society
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    • v.16 no.5
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    • pp.261-263
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    • 2006
  • In order to investigate the magnetic properties of Eu ions in the single crystal $MnF_2$, the temperature dependent magnetic susceptibilities of the antiferromagnetic $MnF_2$ and the single crystal $MnF_2$(1.5% $EuF_3$) with the rutile structures were measured in the temperature range from 4K to 300K. The detailed analysis of the measured susceptibilities showed that the magnetic susceptibility by the doping of the small amount $EuF_3$ in the antiferromagnetic single crystal $MnF_2$ follows the antiferromagnetic Curie-Weiss law with the negative paramagnetic Curie temperature similarly as in $MnF_2$. It was also found that Eu ion has +3 valence. This solves the long standing discrepancy on this problem.