• Title, Summary, Keyword: inverse spinel

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Structural, Magnetic, and Optical Studies on Normal to Inverse Spinel Phase Transition in FexCo3-xO4 Thin Films

  • Kim, Kwang-Joo;Kim, Hee-Kyung;Park, Young-Ran;Ahn, Geun-Young;Kim, Chul-Sung;Park, Jae-Yun
    • Journal of the Korean Magnetics Society
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    • v.15 no.2
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    • pp.96-99
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    • 2005
  • Phase transition from normal- to inverse-spinel structure has been observed for $Fe_xCo_{3-x}O_4$ thin films as the Fe composition (x) increases from 0 to 2. The samples were fabricated as thin films by sol-gel method on Si(100) substrates. X-ray diffraction measurements revealed a coexistence of two phases, normal and inverse spinel, for $0.76{\le}x{\le}0.93$. The normal-spinel phase is dominant for $x{\le}0.55$ while the inverse-spinel phase for $x{\ge}l.22$. The cubic lattice constant of the inverse-spinel phase is larger than that of the normal-spinel phase. For both phases the lattice constant increases with increasing x. X-ray photoelectron spectroscopy measurements revealed that both $Fe^{2+}$ and $Fe^{3+}$ ions exist with similar strength in the x=0.93 sample. Conversion electron $M\ddot{o}ssbauer$ spectra measured on the same sample showed that $Fe^{2+}$ ions prefer the octahedral $Co^{3+}$ sites, indicating the formation of the inverse-spinel phase. Analysis on the measured optical absorption spectra for the samples by spectroscopic ellipsometry indicates the dominance of the normal spinel phase for low x in which $Fe^{3+}$ ions tend to substitute the octahedral sites.

Mossbauer Study for the Cation Distribution of Co-ferrite (CoxFe1-xO4) Thin Films (Co-ferrite 박막에서 양이온 거동에 관한 Mössbauer 분광 연구)

  • Park, Jae-Yun;Park, Young-Ran;Kim, Hee-Kyung;Kim, Kwang-Joo
    • Journal of the Korean Magnetics Society
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    • v.16 no.1
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    • pp.1-5
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    • 2006
  • The crystallographic properties and cation distribution of oxyspinels ferrite $Co_xFe_{1-x}O_4$ thin films have been explored by X-ray diffraction, vibrating sample magnetometer (VSM), and conversion electron $M\"{o}ssbauer$ spectroscopy (CEMS). Thin films are prepared by sol-gel method. Normal spinel structure is transformed to inverse spinel structure with increasing Co concentration CEMS results indicate that most of $Fe^{3+}$ ions are substituted to $Co^{3+}$ions. Accordingly $Co^{2+}$ ions on octahedral site migrate to tetrahedral site. Magnetic moment is decreased with increasing Co concentration, which means high spin $Fe^{3+}$ ions are replaced by low spin $Co^{3+}$.

The Study of Magnetic Structure of Ni1-xMgxFe2O4 Ferrite System by Mössbauer Spectroscopy (Mössbauer 분광법에 의한 Ni1-xMgxFe2O4 Ferrite의 자기구조 연구)

  • Yoon, In-Seop;Baek, Seung-Do
    • Journal of the Korean Magnetics Society
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    • v.19 no.3
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    • pp.106-112
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    • 2009
  • $Ni_{1-x}Mg_xFe_2O_4$ ferrite system was studied by using X-ray diffraction and $M{\ddot{o}}ssbauer$ spectroscopy. The samples were prepared by ceramic sintering method with Mg content x. The X-ray diffraction patterns of samples show phase of cubic spinel structure. There are no remarkable changes of lattice constants in $Ni_{1-x}Mg_xFe_2O_4$ ferrite system. The $M{\ddot{o}}ssbauer$ spectra were consisted of two sets of six lines, respectively, corresponding to $Fe^{3+}$ at tetrahedral and octahedral sites. The magnetic hyperfine field of samples was decreased as increasing Mg contents x in both sites and it was shown Yafet-Kittel magnetic structure. $NiFe_2O_4$ was shown complete inverse spinel, but $NiFe_2O_4$ was shown partial inverse spinel which absorption area ratio (oct/tet) was 1.449 in $M{\ddot{o}}ssbauer$ spectrum.

Cathodoluminescence of $Mg_2$$SnO_4$:Mn,:Mn Green Phosphor under Low-Voltage Electron Excitation ($Mg_2$$SnO_4$:Mn 녹색 형광체의 저전압 음극선 발광 특성)

  • Kim, Gyeong-Nam;Jeong, Ha-Gyun;Park, Hui-Dong;Kim, Do-Jin
    • Korean Journal of Materials Research
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    • v.11 no.9
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    • pp.759-762
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    • 2001
  • Mg$_2$SnO$_4$having an inverse spinel structure was selected as a new host material of $Mn^{2+}$ activator. The luminescence of the $Mg_2$SnO$_4$:Mn phosphor prepared by the solid-state reaction were investigated under ultraviolet and low-voltage electron excitation. The Mn-doped magnesium tin oxide exhibited strong green emission with the spectrum centered at 500nm wavelength. It was explained that the green emission in $Mg_2$SnO$_4$:Mn phosphor is due to energy transfer from $^4T_1to ^6A_1\;of\; Mn^{2+}$ ion at tetrahedral site in the spinel structure. The optimum concentration of $Mn^{2+}$/ion exhibiting maximum emission intensity by the low-voltage electron excitation was 0.6mol%. ?

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Effects of Cr Doping on Magnetic Properties of Inverse Spinel CoFe2O4 Thin Films

  • Kim, Kwang-Joo;Kim, Hee-Kyung;Park, Young-Ran;Park, Jae-Yun
    • Journal of Magnetics
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    • v.11 no.1
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    • pp.51-54
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    • 2006
  • Variation of magnetic properties through Cr substitution for Co in inverse-spinel $CoFe_2O_4$ has been investigated by vibrating-sample magnetometry (VSM) and conversion electron $M\ddot{o}ssbauer$ spectroscopy (CEMS). $Cr_{x}Co_{1-x}Fe_2O_4$ samples were prepared as thin films by a sol-gel method. The lattice constant of the $Cr_{x}Co_{1-x}Fe_2O_4$ samples was found to remain unchanged, explainable in terms of a reduction of tetrahedral $Fe^{3+}$ ion to $Fe^{2+}$ due to substitution of $Cr^{3+}$ ion into octahedral $Co^{2+}$ site. The existence of the tetrahedral $Fe^{2+}$ ions in $Cr_{x}Co_{1-x}Fe_2O_4$ was confirmed by CEMS analysis. Room-temperature magnetic hysteresis curves for the $Cr_{x}Co_{1-x}Fe_2O_4$ films measured by VSM revealed that the saturation magnetization $M_s$ increases by Cr doping. The $M_s$ is maximized when x = 0.1 and decreases for higher x but is still bigger than that of $CoFe_2O_4$. The increase of $M_s$ can be explained partly by the reduction of the tetrahedral $Fe^{3+}$ ion to $Fe^{2+}$.

Electrical and Magnetic Properties of Magnetite Powder during a Verwey Transition (Verwey 전이와 마그네타이트의 전기적 및 자기적 특성)

  • Yoon, Sunghyun
    • New Physics: Sae Mulli
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    • v.68 no.12
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    • pp.1302-1307
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    • 2018
  • The crystallographic, electrical and magnetic behaviors of magnetite powder in the vicinity of its Verwey transition were investigated in this study. Magnetite was prepared by synthesizing a nanoparticle precursor and then annealing it at $800^{\circ}C$ for 1 h under a dynamic vacuum. Crystallographic and morphology analyses were done by using scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical and the magnetic properties were examined by using $M{\ddot{o}}ssbauer$ spectroscopy, vibrating sample magnetometer (VSM) and resistivity measurement. Both the magnetic moment and the resistivity showed discontinuous changes at the Verwey transition temperature ($T_V$). The temperature dependence of magnetic anisotropy constant showed a monotonic decrease with increasing temperature, with slight dip near $T_V$. $M{\ddot{o}}ssbauer$ spectra showed the superposition of two sextets, one from the tetrahedral (A) and the other from the octahedral (B) sites. The results revealed that identical charge states existed in the B site at temperatures both above and below $T_V$. A coordination crossover resulted in a transition from an inverse to a normal spinel at or close to $T_V$.

Titanium Incorporation in (Znl-xNix)2TiO4 Spinel Ceramics (티타늄 합침에 의한 (Znl-xNix)2TiO4 스피넬 세라믹스)

  • 강귀원;김효태;황준철;이종원;백운규
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.97-97
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    • 2003
  • Composition in the (Znl-xNix)2TiO4+ yTiO2 system (x=0-0.5, y=0-0.35) were synthesized via the solid-state reaction route. The incorporation of titanium, in the form of TiO2, in (Znl-xNix)2TiO4 spinel ceramics were investigated by analyzing the crystal structure and measuring the dielectric properties. The result of the crystal structure analysis suggested that TiO2 level of 0.01 y 0.33 could be incorporated into the (Znl-xNix)2TiO4 spinel. The change of incorporated TiO2 level is related with Co-content as a inverse proportion and the variation of lattice parameter and dielectric properties were supported the result.

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