• 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$\AA$ ).

• 한국세라믹학회지
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• 제43권7호
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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.

• 한국자기학회지
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• 제3권1호
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• pp.18-22
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• 1993

$Cu_{x}Zn_{1-x}Fe_{2}O_{4}(0{\leq}x{\leq}1)$의 이온분포 및 자기적 성질을 X-선 회절법과 $M\"{o}ssbauer$ 분광법으로 연구하였다. 결정구조는 $0{\leq}x{\leq}0.9$의 영역에서 입방 스피넬이다. $ZnFe_{2}O_{4}$의 이온분포는 ${(Zn_{1-x}Fe_{x})}_{A}{[Zn_{x}Fe_{2-x}]}_{B}O_{4}$:x=0.1 이다. Curie 온도 이하의 $M\"{o}ssbauer$ spectrum에서 $Fe^{3+}$ 이온의 분포상태를 $0{\leq}x{\leq}1$의 전 영역에서 얻었다. Cu의 농도 x가 증가함에 따라서 사면체자리에 들어가는 $Fe^{3+}$ 이온의 수가 증가하고 Cu-Zn 훼라이트의 Curie 온도가 높아진다.

• 한국자기학회지
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• 제10권4호
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• pp.149-153
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• 2000

변하는 자기장을 단결정 및 다결정 망간 산화물 La$_{0.7}$Ca$_{0.3}$MnO$_3$에 인가하였을 때 자기 엔트로피가 크게 변하는(거대 자기 엔트로피 변화)현상이 관측되었다. 이 거대 자기 엔트로피 변화는 Curie온도에서 유사 1차상전이에 의한 자화값의 급격한 변화에 의한 것으로 추측된다. 이 거대 자기 엔트로피 변화와 망간 산화물 Curie 온도의 100 K＜T＜400 K 내의 조절 용이성은 상온을 포함한 넓은 온도에서 망간 산화물을 이용한 자기 냉각 기관의 개발 가능성을 제시하고 있다. 있다.

• 한국자기학회지
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• 제16권5호
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• pp.261-263
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• 2006

Rutile 구조를 가진 반강자성체 $MnF_2$내에서 Eu의 자기적 성질을 알아내기 위해 단결정 $MnF_2$(1.5% $EuF_3$)의 자기 감수율을 $4{\sim}300K$사이의 온도 구간에서 측정했다. 측정된 자기 감수율의 분석을 통해서 $EuF_3$의 첨가로 추가되는 자기 감수율 역시 $MnF_2$와 마찬가지로 상자성 큐리 온도가 -값을 가지는 반강자성 Curie-Weiss 법칙을 만족하는 것을 확인했다. 또한 Eu의 경우 +3가를 띄고 있는 것을 확인하여 기존의 일치되지 않는 연구들의 문제점을 해결했다.

• 한국결정성장학회지
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• 제3권2호
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• pp.99-106
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• 1993

열분석(DTA : Differential Thermal Analysis) 방법에 의한 퀴리온도$(T_c)$ 측정방법으로부터 48.50에서 49 $Li_2O$ mole %까지의 퀴리온도$(T_c)$와 $Li_2O$ mole %(C)의 관계식 $(T_c = -17.869C^2+1840.2C-46623)$을 구하였다.$LiTaO_3$ 단결정의 congruent 조성을 결정하기 위하여 48.60 부터 48.70 mole %까지의 영역에서 쵸크랄스키법으로 $LiTaO_3$ 단결정을 육성하고 Top과 Tail 결정에서의 퀴리온도 차이,${\Delta}{T_c} (T_{c(Top)}-T{_c(Tail)})$ 그리고 결정성장 초기와 말기의 융액과 결정의 조성비로부터 분배계수(k)를 구하였다. 이 결과로부터 결정된 congruent 조성은 48.65 mole %였으며 그때의 $(T_c)$ 값은 $610{\pm}1^{\circ}C$였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.58-60
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• 1988

The dielectric properties of glass ceramics with BaTiO$_3$ crystallites are described. In this study measurements were made over the frequency range 1kHz-10MHz and temperature range $25^{\circ}C$-15$0^{\circ}C$. There are several minor constituents in the glass which needed to obtain the desired properties. The fluorine ion substitutes for oxygen in glass-crystallized BaTiO$_3$. And additions of Mg ion is used to shift the Curie temperature. We show the addition of Mg ion lowers the Curie point to about 323。K.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.684-688
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• 2001

The structural, piezoelectric and dynamic range characteristics of modified PbTi $O_3$ceramics were investigated as a function of Mn $O_2$addition. With the increase of Mn $O_2$addition, Curie temperature was decreased. As the increase of Mn $O_2$addition, mechanical quality factor ( $Q_{mt3}$) in the third over tone thickness mode was increased. Dynamic range in the third over tone thickness mode was also increased with the increase of Mn $O_2$addition. The composition ceramics added to 0.075wt% Mn $O_2$showed the best properties for SMD type resonator using third over tone thickness vibration in terms of high Curie temperature more than 31$0^{\circ}C$ and dynamic range of 49.38dB.B.

• 한국세라믹학회지
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• 제28권9호
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• pp.689-695
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• 1991

Dielectric properties of Ba1-$\chi$Sr$\chi$Ti1-yCayO3-y ceramics, where Sr and Ca were doped to Ba-site and Ti-site within the range of 0 x 0.24 and 0 y 0.05, respectively, were investigated. The substitution of Ca for Ti, which maintained the high resistivity of these formulations after sintering in a reducing atmosphere, was confirmed. Ca addition decreased the tetragonality c/a, increased the unit cell volume, and lowered Curie temperature, which were attributed to the occupancy of Ca2+ ions on Ti-sites. The lowering of Curie temperature by Ca addition was affected by the substitution of Sr for Ba-site; within 2 mol% of Ca, Curie temperature was lowered at a rate of 2$0^{\circ}C$ and 16$^{\circ}C$ per mol% of Ca at x=0 and x=0.08, respectively. Whereas the resistivity of the formulations without Ca was reduced to 107 {{{{ OMEGA }}cm, when sintered at low oxygen partial pressure of 10-9 MPa, the resistivity value higher than 1011 {{{{ OMEGA }}cm was maintained for the formulations containing Ca more than 0.5 mol%. Dielectric loss factor, tan$\delta$, was about 1% for most formulations.

• 한국세라믹학회지
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• 제35권2호
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• pp.123-128
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• 1998

Multilayer ceramic capacitors(MLCC) were prepared by laminating the layer of composition with dif-ferent Curie temperature to improve temperature coefficient in the Pb(Mg1/3Nb2/3)O3-PbTiO3 binary system. Green sheet was formed by tape casting using Pb(Mg1/3Nb2/3)O3-PbTiO3 and PbTiO3 synthesized with solid state reaction of PBO. Nb2O5 MgO and TiO2. Green sheet with electrode of 70Ag-30Pd was laminated under 300 kg/cm2 at 70$^{\circ}C$ and sintered at 1100$^{\circ}C$ for 2hr. Curie temperatues for MLCC with 10 layers of pure PMN and 0.9PMN-0.1PT were lowered to -22$^{\circ}C$ and 36$^{\circ}C$ respectively. MLCC with 7 layers of PMN and 3 layers of 0.9PMN-0.1PT showed nearly zero temperature coefficient of capacitance in the range of -20∼30$^{\circ}C$ and sum of dissipation factor of each layer.