• Title, Summary, Keyword: Ordered perovskite

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Magnetic Property of Oxide with the Perovskite Structure, $A_2Fe(III)BO_6$ (A = Ca, Sr, Ba and B = Sb, Bi)

  • 이성옥;조태연;변송호
    • Bulletin of the Korean Chemical Society
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    • v.18 no.1
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    • pp.91-97
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    • 1997
  • In the course of magnetic study on several perovskite-type oxides, A2Fe(Ⅲ)BO6 (A = Ca, Sr, Ba and B = Sb, Bi), we have observed a strong irreversibility in their dc-magnetizations. When the structural data and the Mossbauer spectra are considered, such an irreversibility is to be associated with some competitions between the nearest-neighbors (nn) and the next-nearest-neighbors (nnn) in their magnetic sublattices. Particularly, the Mossbauer spectra indicate that Sr2FeBiO6 of cubic perovskite-structure is apparently well ordered crystalline compound. Nontheless this antiferromagnet shows a magnetic property which resembles that of a spin-glass. The strong history dependence is observed below 91 K and the irreversible magnetic behavior is also observed from the measurement of hysteresis loops at 10 K after zero-field-cooled (zfc) and field-cooled (fc) processes. Considering the nn and the nnn superexchanges of almost same order in ordered perovskite, it is proposed that there exists a competition and cancellation of antiferromagnetic and ferromagnetic superexchange between the nearest-neighbors and the next-nearest-neighbors, thus introducing a certain degree of frustration.

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Structural Ordering Effect on Photoluminescence Properties of $Eu^{3+}$ Doped Perovskite Tungstate $A_2BWO_6$ System

  • Yo, Chul-Hyun
    • Journal of Photoscience
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    • v.5 no.4
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    • pp.153-155
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    • 1998
  • The optical spectroscopic properties of the ordered perovskite structure A2BWO6 doped with Eu3+ have been studied. The experimental result about Eu3+ ordering in the system of A2BWO6 indicate the different structural conditions. Some influence of Eu3+ substitutioin on the different types of cation site have been investigated.

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Stbilization of Perovskite Phase and Enhanced DPT Characteristics of $Pb(Zn, Mg)_{1/3}Nb_{2/3}O_3-PbTiO_3$ Ceramics by the Additionof Excess Constituent Oxides ($Pb(Zn, Mg)_{1/3}Nb_{2/3}O_3-PbTiO_3$계에서 구성 산화물 첨가에 따른 Perovskite상 안정화 및 DPT성 증대 효과)

  • 이규만;장현명;유병두
    • Journal of the Korean Ceramic Society
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    • v.30 no.11
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    • pp.925-932
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    • 1993
  • The perovskite phase in PZN-PMN-PT (Pb(Zn, Mg)1/3Nb2/3O3-PbTiO3) pseudoternary ceramics was stabilized by the addition of excess constituent divalent oxides (PbO, MgO and ZnO). The excess addition of 5mol% MgO or 7.5mol% PbO fully stabilized the perovskite phase. The enhanced diffuse phase transition (DPT) and the decrease in the electrical resistivity observed in the presence of excess ZnO or MgO were interpreted in terms of the additional formation of negatively charged, short-range ordered 1:1 domains with a concomitant generation of charge carriers, holes.

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Colossal magnetoresistance of double-ordered perovskite $Sr_{2}FeMoO_{6}$ ceramics and sputter-deposited films ($Sr_{2}FeMoO_{6}$ 소결체와 스퍼터링법으로 제조된 박막의 초거대자기저항현상에 관한 연구)

  • 이원종;장원위
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.12 no.1
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    • pp.36-41
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    • 2002
  • Abstract The stoichiometric and double-ordered perovskite $Sr_2FeMoO_6$ (SFMO) polycrystalline ceramics were fabricated by sintering at above $900^{\circ}C$ in $H_2$(5%)/Ar reductive ambient. SMO polycrystals showed good ferromagnetic properties andmagnetrotesistqnce ratios of about 15 % at 8K and 3 % at room temperature. Amorphous SFMO thin films were deposited on $LaA1O_3$ and $SrTiO_3$ single crystal substrates using rf sputtering method with the SFMO polycrystalline ceramic target. Double-ordered perovskite polycrystalline SFMO thin films were fabricated by solid state crystallization by annealing the deposited amorphous films at above $680^{\circ}C$ in $H_2$(5%)/Ar reductive ambient. SFMO thin films exhibited ferromagnetic behavior. Their magnetroresistance ratios, however, were only 0.3~0.5% at 8K and disappeared with increasing the measuring temperature. This was attributed to the absence of magnetic spin tunneling between grains due to the porous structure and non-stoichiometric composition of the deposited films.

Crystal structure of $Ba(Mg_{1/3}Nb_{2/3})O_3$ - $La(Mg_{2/3}Nb_{1/3})O_3$ Complex perovskite compound ($Ba(Mg_{1/3}Nb_{2/3})O_3$ - $La(Mg_{2/3}Nb_{1/3})O_3$ 복합 페로브스카이트 화합물의 결정구조)

  • Paik, Jong-Hoo;Lee, Mi-Jae;Choi, Byung-Hyun;Lee, Jong-Won;Jee, Mi-Jung;Lim, Eun-Kyeong;Nahm, Sahn;Lee, Hwack-Joo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.283-287
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    • 2003
  • Crystal structure of $(Ba_{1-x}La_x)[Mg_{(1+x)/3}Nb_{(2-x)/3}]O_3$ (BLMN) ceramics with $0{\leq}x{\leq}1$ was investigated using synchrotron X-ray powder diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). When La content, x, is above 0.1, the 1:2 ordered hexagonal structure found in $Ba(Mg_{1/3}Nb_{2/3})O_3$ (BMN) was transformed into 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x=0.7. However, when x exceeded 0.7, BLMN was transformed 1:1 ordered structure which has cation displacement and in-phase and anti-phase tilt of octahedra.

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A Study on the Ordering of Na Ions in $Na_xWO_3(0.5{\leq}x{\leq}1.0)$

  • Na, Jong-Chul;Sahn Nahm;Kim, Myong-Ho;Lee, Hyack-Joo;Byun, Jae-Dong
    • The Korean Journal of Ceramics
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    • v.2 no.3
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    • pp.157-161
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    • 1996
  • Cry structures of $Na_xWO_3$ (0.5$\leq$x$\leq$1.0) were investigated. Transmission electron microscopy (TEM) studies indicate that there is an ordering of sodium ions when x=0.75. The direction of ordering is [110] and the wavelength of ordering is twice of the interplanar distance of (110) plane. It has been confirmed that a superlattice containing eight $Na_{0.75}WO_3$ is the unit cell of ordered structure. In this unit cell, Na sites at (000) and ($\frac{2}{1}\frac{2}{1}\frac{2}{1}$) are vacant. The ordered phase was preserved after the annealing at $600^{\circ}C$ in the air. In reduced $Na_xWO_3$ with x=0.5 and 1.0, extra phases were found with the partially ordered perovskite phase. After annealing at $600^{\circ}C$, theses phases transformed to the phases found in calcined specimens.

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Ordering Structures of B-Site Cations in Pb(${Mg_{1/3}}{Nb_{2/3}}$)$O_3$-Based Solid Solutions (Pb(${Mg_{1/3}}{Nb_{2/3}}$)$O_3$계 고용체의 B자리 양이온 질서배열구조)

  • 차석배;김병국;제해준
    • Journal of the Korean Ceramic Society
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    • v.37 no.5
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    • pp.491-496
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    • 2000
  • Single phae Pb(Mg1/3Nb2/3)O3-based solid solutions, the Mg2+ of which are replaced by 20mol% of Ni2+, Zn2+, Cd2+, and the Pb2+ of which are replaced by 0∼20 mol% of La3+, were synthesized and their ordering structures of B-site cations were investigated by XRD and TEM. The B'-site cations (Mg2+, Ni2+, Zn2+, Cd2+) are disordered while these B'-site cations and the B"-site cations (Nb5+) are nonstoichiometrically 1:1 ordered within the ordered nano-domains dispersed in the Nb5+-rich disordered matrix. The charge imbalance between the B'-rich ordered nano-domains and the B"-rich disordered matrix are compensated by the doping of electron donor such as La3+, which enhances the degree of nonstoichiometric 1:1 ordering. For a given La3+ content, the degree of nonstoichiometric 1:1 ordering increases as the average ionic size difference between the B'-and B"-site cations increases, Ni2+

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Observation of Piezomagnetism in a Heisenberg Paramagnet

  • Lee, Kyu Won;Lee, Chang Hoon;Lee, Cheol Eui
    • Journal of Magnetics
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    • v.7 no.1
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    • pp.1-3
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    • 2002
  • Piezomagnetic behaviors have been observed far above the Neel temperature in the perovskite-type layer structure compound $(C_{18}H_{37}NH_3)_2MnCl_4$undergoing structural phase transitions. Our observations were well explained by the magnetic and the structural orders coupled together via a magnetostructural coupling attributable to the Dzyaloshinsky-Moriya interaction.