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Kazuyuki Hirao - One of the best experts on this subject based on the ideXlab platform.
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn K and Fe K x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite (ZnFe{sub 2}O{sub 4}) thin film prepared by a sputtering method, ZnFe{sub 2}O{sub 4} thin films annealed at elevated temperatures, and ZnFe{sub 2}O{sub 4} bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at 800 deg. C as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for Zn{sup 2+} on the tetrahedral site (A site) or that for Fe{sup 3+} on the octahedral site (B site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the A and B sites. The degree of cation disordering, x, defined as [Zn{sub 1-x}{sup 2+}Fe{sub x}{sup 3+}]{sub A}[Zn{sub x}{sup 2+}Fe{sub 2-x}{sup 3+}]{sub B}O{sub 4}, is estimated to bemore » approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn K edge. Curious magnetic properties as we previously observed for the as-deposited thin film--i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior--are discussed in connection with disordering of Zn{sup 2+} and Fe{sup 3+} ions in the spinel-type structure.« less
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn $K$ and Fe $K$ x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite $(\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})$ thin film prepared by a sputtering method, $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ thin films annealed at elevated temperatures, and $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for ${\mathrm{Zn}}^{2+}$ on the tetrahedral site ($A$ site) or that for ${\mathrm{Fe}}^{3+}$ on the octahedral site ($B$ site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the $A$ and $B$ sites. The degree of cation disordering, $x$, defined as ${[\mathrm{Zn}_{1\ensuremath{-}x}{}^{2+}\mathrm{Fe}_{x}{}^{3+}]}_{A}{[\mathrm{Zn}_{x}{}^{2+}\mathrm{Fe}_{2\ensuremath{-}x}{}^{3+}]}_{B}{\mathrm{O}}_{4}$, is estimated to be approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn $K$ edge. Curious magnetic properties as we previously observed for the as-deposited thin film---i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior---are discussed in connection with disordering of ${\mathrm{Zn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions in the spinel-type structure.
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large faraday effect in a short wavelength range for disordered Zinc Ferrite thin films
Journal of Applied Physics, 2006Co-Authors: Katsuhisa Tanaka, Seisuke Nakashima, Koji Fujita, Kazuyuki HiraoAbstract:We have prepared a Zinc Ferrite (ZnF2O4) thin film 85nm thick deposited on a silica glass substrate by using a radio frequency sputtering method. Faraday effect measurements have been carried out not only for as-deposited but also for annealed thin films. The thin film annealed at 300°C as well as the as-deposited thin film exhibit a large Faraday rotation angle at a wavelength of around 390nm. In particular, the thin film annealed at 300°C manifests the largest Faraday effect among the present thin films; the rotation angle of 1.65°∕μm is attained at a wavelength of 386nm. The thin films 1.08μm thick exhibit a large magnetization at room temperature, and the dependence of the magnetization on the external magnetic field is suggestive of a ferrimagnetic behavior.
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high magnetization and the high temperature superparamagnetic transition with intercluster interaction in disordered Zinc Ferrite thin film
Journal of Physics: Condensed Matter, 2005Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Koji Fujita, Kazuyuki HiraoAbstract:Magnetic properties have been investigated for a Zinc Ferrite thin film deposited on glass at a substrate temperature close to room temperature using a sputtering method. X-ray diffraction analysis reveals that the thin film consists of nanocrystalline ZnFe2O4 with the size of approximately 10 nm. The magnetization at 300 K as a function of the external magnetic field shows ferrimagnetic behaviour, and tends to be saturated to the high value of 32 emu g−1 when the external magnetic field is higher than 30 kOe. It is considered that the preparation of the ZnFe2O4 thin film by the sputtering method, which involves very rapid cooling of vapour to form the solid-state phase, causes the random distribution of Zn2+ and Fe3+ ions in the spinel structure. In such a situation, Fe3+ ions occupy both octahedral and tetrahedral sites, and the strong superexchange interaction among them gives rise to ferrimagnetic properties accompanied with high magnetization. The static and dynamic magnetic responses, such as the frequency dependence of the linear ac susceptibility, the temperature dependence of the nonlinear ac susceptibility, the discrepancy between the zero-field-cooled (ZFC) and field-cooled dc magnetizations, and the relaxation of the ZFC magnetization, demonstrate that the magnetism of the present thin film is attributable to the superparamagnetism with the interaction among magnetic clusters. Spin freezing occurs at a temperature higher than room temperature ( K).
Seisuke Nakashima - One of the best experts on this subject based on the ideXlab platform.
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn K and Fe K x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite (ZnFe{sub 2}O{sub 4}) thin film prepared by a sputtering method, ZnFe{sub 2}O{sub 4} thin films annealed at elevated temperatures, and ZnFe{sub 2}O{sub 4} bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at 800 deg. C as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for Zn{sup 2+} on the tetrahedral site (A site) or that for Fe{sup 3+} on the octahedral site (B site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the A and B sites. The degree of cation disordering, x, defined as [Zn{sub 1-x}{sup 2+}Fe{sub x}{sup 3+}]{sub A}[Zn{sub x}{sup 2+}Fe{sub 2-x}{sup 3+}]{sub B}O{sub 4}, is estimated to bemore » approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn K edge. Curious magnetic properties as we previously observed for the as-deposited thin film--i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior--are discussed in connection with disordering of Zn{sup 2+} and Fe{sup 3+} ions in the spinel-type structure.« less
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn $K$ and Fe $K$ x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite $(\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})$ thin film prepared by a sputtering method, $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ thin films annealed at elevated temperatures, and $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for ${\mathrm{Zn}}^{2+}$ on the tetrahedral site ($A$ site) or that for ${\mathrm{Fe}}^{3+}$ on the octahedral site ($B$ site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the $A$ and $B$ sites. The degree of cation disordering, $x$, defined as ${[\mathrm{Zn}_{1\ensuremath{-}x}{}^{2+}\mathrm{Fe}_{x}{}^{3+}]}_{A}{[\mathrm{Zn}_{x}{}^{2+}\mathrm{Fe}_{2\ensuremath{-}x}{}^{3+}]}_{B}{\mathrm{O}}_{4}$, is estimated to be approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn $K$ edge. Curious magnetic properties as we previously observed for the as-deposited thin film---i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior---are discussed in connection with disordering of ${\mathrm{Zn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions in the spinel-type structure.
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large faraday effect in a short wavelength range for disordered Zinc Ferrite thin films
Journal of Applied Physics, 2006Co-Authors: Katsuhisa Tanaka, Seisuke Nakashima, Koji Fujita, Kazuyuki HiraoAbstract:We have prepared a Zinc Ferrite (ZnF2O4) thin film 85nm thick deposited on a silica glass substrate by using a radio frequency sputtering method. Faraday effect measurements have been carried out not only for as-deposited but also for annealed thin films. The thin film annealed at 300°C as well as the as-deposited thin film exhibit a large Faraday rotation angle at a wavelength of around 390nm. In particular, the thin film annealed at 300°C manifests the largest Faraday effect among the present thin films; the rotation angle of 1.65°∕μm is attained at a wavelength of 386nm. The thin films 1.08μm thick exhibit a large magnetization at room temperature, and the dependence of the magnetization on the external magnetic field is suggestive of a ferrimagnetic behavior.
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high magnetization and the high temperature superparamagnetic transition with intercluster interaction in disordered Zinc Ferrite thin film
Journal of Physics: Condensed Matter, 2005Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Koji Fujita, Kazuyuki HiraoAbstract:Magnetic properties have been investigated for a Zinc Ferrite thin film deposited on glass at a substrate temperature close to room temperature using a sputtering method. X-ray diffraction analysis reveals that the thin film consists of nanocrystalline ZnFe2O4 with the size of approximately 10 nm. The magnetization at 300 K as a function of the external magnetic field shows ferrimagnetic behaviour, and tends to be saturated to the high value of 32 emu g−1 when the external magnetic field is higher than 30 kOe. It is considered that the preparation of the ZnFe2O4 thin film by the sputtering method, which involves very rapid cooling of vapour to form the solid-state phase, causes the random distribution of Zn2+ and Fe3+ ions in the spinel structure. In such a situation, Fe3+ ions occupy both octahedral and tetrahedral sites, and the strong superexchange interaction among them gives rise to ferrimagnetic properties accompanied with high magnetization. The static and dynamic magnetic responses, such as the frequency dependence of the linear ac susceptibility, the temperature dependence of the nonlinear ac susceptibility, the discrepancy between the zero-field-cooled (ZFC) and field-cooled dc magnetizations, and the relaxation of the ZFC magnetization, demonstrate that the magnetism of the present thin film is attributable to the superparamagnetism with the interaction among magnetic clusters. Spin freezing occurs at a temperature higher than room temperature ( K).
Katsuhisa Tanaka - One of the best experts on this subject based on the ideXlab platform.
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn K and Fe K x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite (ZnFe{sub 2}O{sub 4}) thin film prepared by a sputtering method, ZnFe{sub 2}O{sub 4} thin films annealed at elevated temperatures, and ZnFe{sub 2}O{sub 4} bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at 800 deg. C as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for Zn{sup 2+} on the tetrahedral site (A site) or that for Fe{sup 3+} on the octahedral site (B site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the A and B sites. The degree of cation disordering, x, defined as [Zn{sub 1-x}{sup 2+}Fe{sub x}{sup 3+}]{sub A}[Zn{sub x}{sup 2+}Fe{sub 2-x}{sup 3+}]{sub B}O{sub 4}, is estimated to bemore » approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn K edge. Curious magnetic properties as we previously observed for the as-deposited thin film--i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior--are discussed in connection with disordering of Zn{sup 2+} and Fe{sup 3+} ions in the spinel-type structure.« less
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn $K$ and Fe $K$ x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite $(\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})$ thin film prepared by a sputtering method, $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ thin films annealed at elevated temperatures, and $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for ${\mathrm{Zn}}^{2+}$ on the tetrahedral site ($A$ site) or that for ${\mathrm{Fe}}^{3+}$ on the octahedral site ($B$ site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the $A$ and $B$ sites. The degree of cation disordering, $x$, defined as ${[\mathrm{Zn}_{1\ensuremath{-}x}{}^{2+}\mathrm{Fe}_{x}{}^{3+}]}_{A}{[\mathrm{Zn}_{x}{}^{2+}\mathrm{Fe}_{2\ensuremath{-}x}{}^{3+}]}_{B}{\mathrm{O}}_{4}$, is estimated to be approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn $K$ edge. Curious magnetic properties as we previously observed for the as-deposited thin film---i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior---are discussed in connection with disordering of ${\mathrm{Zn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions in the spinel-type structure.
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large faraday effect in a short wavelength range for disordered Zinc Ferrite thin films
Journal of Applied Physics, 2006Co-Authors: Katsuhisa Tanaka, Seisuke Nakashima, Koji Fujita, Kazuyuki HiraoAbstract:We have prepared a Zinc Ferrite (ZnF2O4) thin film 85nm thick deposited on a silica glass substrate by using a radio frequency sputtering method. Faraday effect measurements have been carried out not only for as-deposited but also for annealed thin films. The thin film annealed at 300°C as well as the as-deposited thin film exhibit a large Faraday rotation angle at a wavelength of around 390nm. In particular, the thin film annealed at 300°C manifests the largest Faraday effect among the present thin films; the rotation angle of 1.65°∕μm is attained at a wavelength of 386nm. The thin films 1.08μm thick exhibit a large magnetization at room temperature, and the dependence of the magnetization on the external magnetic field is suggestive of a ferrimagnetic behavior.
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high magnetization and the high temperature superparamagnetic transition with intercluster interaction in disordered Zinc Ferrite thin film
Journal of Physics: Condensed Matter, 2005Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Koji Fujita, Kazuyuki HiraoAbstract:Magnetic properties have been investigated for a Zinc Ferrite thin film deposited on glass at a substrate temperature close to room temperature using a sputtering method. X-ray diffraction analysis reveals that the thin film consists of nanocrystalline ZnFe2O4 with the size of approximately 10 nm. The magnetization at 300 K as a function of the external magnetic field shows ferrimagnetic behaviour, and tends to be saturated to the high value of 32 emu g−1 when the external magnetic field is higher than 30 kOe. It is considered that the preparation of the ZnFe2O4 thin film by the sputtering method, which involves very rapid cooling of vapour to form the solid-state phase, causes the random distribution of Zn2+ and Fe3+ ions in the spinel structure. In such a situation, Fe3+ ions occupy both octahedral and tetrahedral sites, and the strong superexchange interaction among them gives rise to ferrimagnetic properties accompanied with high magnetization. The static and dynamic magnetic responses, such as the frequency dependence of the linear ac susceptibility, the temperature dependence of the nonlinear ac susceptibility, the discrepancy between the zero-field-cooled (ZFC) and field-cooled dc magnetizations, and the relaxation of the ZFC magnetization, demonstrate that the magnetism of the present thin film is attributable to the superparamagnetism with the interaction among magnetic clusters. Spin freezing occurs at a temperature higher than room temperature ( K).
Isao Tanaka - One of the best experts on this subject based on the ideXlab platform.
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn K and Fe K x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite (ZnFe{sub 2}O{sub 4}) thin film prepared by a sputtering method, ZnFe{sub 2}O{sub 4} thin films annealed at elevated temperatures, and ZnFe{sub 2}O{sub 4} bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at 800 deg. C as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for Zn{sup 2+} on the tetrahedral site (A site) or that for Fe{sup 3+} on the octahedral site (B site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the A and B sites. The degree of cation disordering, x, defined as [Zn{sub 1-x}{sup 2+}Fe{sub x}{sup 3+}]{sub A}[Zn{sub x}{sup 2+}Fe{sub 2-x}{sup 3+}]{sub B}O{sub 4}, is estimated to bemore » approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn K edge. Curious magnetic properties as we previously observed for the as-deposited thin film--i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior--are discussed in connection with disordering of Zn{sup 2+} and Fe{sup 3+} ions in the spinel-type structure.« less
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn $K$ and Fe $K$ x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite $(\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})$ thin film prepared by a sputtering method, $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ thin films annealed at elevated temperatures, and $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for ${\mathrm{Zn}}^{2+}$ on the tetrahedral site ($A$ site) or that for ${\mathrm{Fe}}^{3+}$ on the octahedral site ($B$ site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the $A$ and $B$ sites. The degree of cation disordering, $x$, defined as ${[\mathrm{Zn}_{1\ensuremath{-}x}{}^{2+}\mathrm{Fe}_{x}{}^{3+}]}_{A}{[\mathrm{Zn}_{x}{}^{2+}\mathrm{Fe}_{2\ensuremath{-}x}{}^{3+}]}_{B}{\mathrm{O}}_{4}$, is estimated to be approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn $K$ edge. Curious magnetic properties as we previously observed for the as-deposited thin film---i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior---are discussed in connection with disordering of ${\mathrm{Zn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions in the spinel-type structure.
Koji Fujita - One of the best experts on this subject based on the ideXlab platform.
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn K and Fe K x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite (ZnFe{sub 2}O{sub 4}) thin film prepared by a sputtering method, ZnFe{sub 2}O{sub 4} thin films annealed at elevated temperatures, and ZnFe{sub 2}O{sub 4} bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at 800 deg. C as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for Zn{sup 2+} on the tetrahedral site (A site) or that for Fe{sup 3+} on the octahedral site (B site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the A and B sites. The degree of cation disordering, x, defined as [Zn{sub 1-x}{sup 2+}Fe{sub x}{sup 3+}]{sub A}[Zn{sub x}{sup 2+}Fe{sub 2-x}{sup 3+}]{sub B}O{sub 4}, is estimated to bemore » approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn K edge. Curious magnetic properties as we previously observed for the as-deposited thin film--i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior--are discussed in connection with disordering of Zn{sup 2+} and Fe{sup 3+} ions in the spinel-type structure.« less
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first principles xanes simulations of spinel Zinc Ferrite with a disordered cation distribution
Physical Review B, 2007Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Tomoyuki Yamamoto, Koji Fujita, Kazuyuki Hirao, Isao TanakaAbstract:Theoretical calculations of Zn $K$ and Fe $K$ x-ray absorption near-edge structures (XANES) using a first-principles method have been performed to evaluate the degree of cation disordering in spinel Zinc Ferrite $(\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})$ thin film prepared by a sputtering method, $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ thin films annealed at elevated temperatures, and $\mathrm{Zn}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bulk specimen prepared by a solid-state reaction. Using the full-potential linearized augmented plane-wave + local orbitals method, a theoretical spectrum is generated for the tetrahedral and octahedral environments for each of the two cations. The experimental XANES spectrum of the thin film annealed at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ as well as that of bulk specimen is successfully reproduced by using either the theoretical spectrum for ${\mathrm{Zn}}^{2+}$ on the tetrahedral site ($A$ site) or that for ${\mathrm{Fe}}^{3+}$ on the octahedral site ($B$ site), which is indicative of the normal spinel structure. For the as-deposited film, on the other hand, excellent agreement between theoretical and experimental spectra is obtained by considering the presence of either ion in both the $A$ and $B$ sites. The degree of cation disordering, $x$, defined as ${[\mathrm{Zn}_{1\ensuremath{-}x}{}^{2+}\mathrm{Fe}_{x}{}^{3+}]}_{A}{[\mathrm{Zn}_{x}{}^{2+}\mathrm{Fe}_{2\ensuremath{-}x}{}^{3+}]}_{B}{\mathrm{O}}_{4}$, is estimated to be approximately 0.6 in the as-deposited film, which is consistent with the analysis of the extended x-ray absorption fine structure on the Zn $K$ edge. Curious magnetic properties as we previously observed for the as-deposited thin film---i.e., ferrimagnetic behaviors accompanied by large magnetization at room temperature and cluster spin-glass-like behavior---are discussed in connection with disordering of ${\mathrm{Zn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions in the spinel-type structure.
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large faraday effect in a short wavelength range for disordered Zinc Ferrite thin films
Journal of Applied Physics, 2006Co-Authors: Katsuhisa Tanaka, Seisuke Nakashima, Koji Fujita, Kazuyuki HiraoAbstract:We have prepared a Zinc Ferrite (ZnF2O4) thin film 85nm thick deposited on a silica glass substrate by using a radio frequency sputtering method. Faraday effect measurements have been carried out not only for as-deposited but also for annealed thin films. The thin film annealed at 300°C as well as the as-deposited thin film exhibit a large Faraday rotation angle at a wavelength of around 390nm. In particular, the thin film annealed at 300°C manifests the largest Faraday effect among the present thin films; the rotation angle of 1.65°∕μm is attained at a wavelength of 386nm. The thin films 1.08μm thick exhibit a large magnetization at room temperature, and the dependence of the magnetization on the external magnetic field is suggestive of a ferrimagnetic behavior.
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high magnetization and the high temperature superparamagnetic transition with intercluster interaction in disordered Zinc Ferrite thin film
Journal of Physics: Condensed Matter, 2005Co-Authors: Seisuke Nakashima, Katsuhisa Tanaka, Koji Fujita, Kazuyuki HiraoAbstract:Magnetic properties have been investigated for a Zinc Ferrite thin film deposited on glass at a substrate temperature close to room temperature using a sputtering method. X-ray diffraction analysis reveals that the thin film consists of nanocrystalline ZnFe2O4 with the size of approximately 10 nm. The magnetization at 300 K as a function of the external magnetic field shows ferrimagnetic behaviour, and tends to be saturated to the high value of 32 emu g−1 when the external magnetic field is higher than 30 kOe. It is considered that the preparation of the ZnFe2O4 thin film by the sputtering method, which involves very rapid cooling of vapour to form the solid-state phase, causes the random distribution of Zn2+ and Fe3+ ions in the spinel structure. In such a situation, Fe3+ ions occupy both octahedral and tetrahedral sites, and the strong superexchange interaction among them gives rise to ferrimagnetic properties accompanied with high magnetization. The static and dynamic magnetic responses, such as the frequency dependence of the linear ac susceptibility, the temperature dependence of the nonlinear ac susceptibility, the discrepancy between the zero-field-cooled (ZFC) and field-cooled dc magnetizations, and the relaxation of the ZFC magnetization, demonstrate that the magnetism of the present thin film is attributable to the superparamagnetism with the interaction among magnetic clusters. Spin freezing occurs at a temperature higher than room temperature ( K).
