Tomo Katsura - Academia.edu (original) (raw)
Papers by Tomo Katsura
The method is described which utilizes slow (10-100 mHz) AC current to determine the electrical c... more The method is described which utilizes slow (10-100 mHz) AC current to determine the electrical conductivity of ferromagnesian minerals at pressures up to 23 GPa and temperatures of 300-2000 K in the 6-8 type multi-anvil highpressure apparatus. The oxidation state of the sample is controlled just below IW buffer. The range of electrical conductivity which can be measured using the present method is 10052-5MS2. An example of measurement was conducted for Mg0.93Fe0.07SiO3 ilmenite. [electrical conductivity, ferromagnesian mineral, oxidation state, high temperature, multi-anvil press]
In this decade, attainable pressure range in a Kawai-type high-pressure apparatus equipped with s... more In this decade, attainable pressure range in a Kawai-type high-pressure apparatus equipped with sintered diamond as second stage anvil is significantly increased and we generated pressure to 97.2 GPa measured by in situ X-ray observation at SPring-8. By using this technique, we measured compressibility of (Fe 0.08 Mg 0.92)SiO 3 perovskite up to more than 90 GPa. The bulk modulus and its pressure derivative are determined to be 268 GPa and 3.8, respectively. These values are slightly different from previous results. However, we obtained consistent results with previous study of bulk modulus of 257 GPa and pressure derivative of 4.3 when we fitted the data in the pressure range less than 70 GPa. The change of compressibility may indicate the spin transition in Fe-bearing perovskite around 70 GPa as suggested by previous study, for example, electrical conductivity measurement, X-ray emission method and so on. [Kawai-type multianvil apparatus, sintered diamond anvil, pressure generation, perovskite, compressibility]
Earth and Planetary Science Letters, 2014
Proceedings of the Japan Academy. Ser. B: Physical and Biological Sciences, 1991
Reaction between molten iron and silicate at high pressure and temperature was examined by employ... more Reaction between molten iron and silicate at high pressure and temperature was examined by employing a mixture of pure iron and (Mg0 9Fe01)2SiO4 olivine as the starting material. The experimental charge quenched at 24 GPa and 2550°C demonstrated that certain amount of Si02 component (at least 2 wt% of Si) dissolved into molten iron from the silicate melt. It is suggested that the dissolving would be enhanced with increasing pressure. The experimental results indicate that Si and 0 are the important alloying light-elements in the earth's core if the core segregation proceeded in the magma ocean of the proto-earth. Concurrently, Si02 contents of the mantle should be substantially reduced from its primitive content.
Physical Review B, 2013
Ferromagnetism in perovskites RTiO 3 can be induced by a steric effect. How the subtle local stru... more Ferromagnetism in perovskites RTiO 3 can be induced by a steric effect. How the subtle local structural change can induce 3D ferromagnetic coupling through Ti-O-Ti superexchange interactions remains controversial. The critical behavior study for the ferromagnetic phase has been made so far only on YTiO 3 since the magnetization measurements are plagued by the contribution from magnetic rare earth. Here we report critical exponents for most ferromagnetic members in the RTiO 3 family by measuring magnetocaloric effect and applying the corresponding scaling laws. Our results indicate that the ferromagnetic coupling in the RTiO 3 can be well-described by the 3D Heisenberg model.
Geophysical Research Letters, 2004
The elastic moduli of polycrystalline wadsleyite, β-(Mg 0.91 Fe 0.09) 2 SiO 4 , were measured up ... more The elastic moduli of polycrystalline wadsleyite, β-(Mg 0.91 Fe 0.09) 2 SiO 4 , were measured up to 470 K by means of the resonant sphere technique. The adiabatic bulk (K S) and shear (µ) moduli were found to be 165.72(6) and 105.43(2) GPa at room temperature. The average slopes (dK S /dT and dµ/dT) in the range were determined to be-0.0175(3) and-0.0159(1) GPa/K. We estimated that the P-, S-wave velocity and density jumps for the αto β-phase transformation at the 410-km depth condition were 9.5, 11.2 and 5.4 %, respectively. These results suggest that the olivine component at the depth should be 52 and 42 volume % for P-and S-waves. 1. Introduction The 410-km discontinuity in the upper mantle is thought to be caused by the transformation of olivine (α-phase) to wadsleyite (β-phase) (Ringwood, 1975). Pyroxene may transform to garnet phase [cf. Irifune and Isshiki, 1998]. But this may affect slopes of velocities and may be excluded in discussion based on the discontinuous change. Comparing the velocity
Geophysical Journal International, 1995
Thermal diffusivity of olivine with (Mg,) xsFeo , I)2Si04 composition is measured at pressures up... more Thermal diffusivity of olivine with (Mg,) xsFeo , I)2Si04 composition is measured at pressures up to 9 GPa and temperatures up to 1700 K using the Angstrom method in a cylindrical geometry. The experimental results demonstrate that lattice thermal diffusivity increases with increasing pressure at a small rate: 46 per cent increase over 10 GPa. The experimental data also suggest that radiative thermal diffusivity may decrease with increasing pressure. Thermal diffusivity in the upper mantle has almost constant values of 7-8 X
![Research paper thumbnail of Corrigendum to “The effect of water on the electrical conductivity of olivine aggregates and its implications for the electrical structure in the upper mantle” [Earth Planet. Sci. Lett. 288 (2009) 291–300]](https://attachments.academia-assets.com/80824345/thumbnails/1.jpg)
](Earth and Planetary Science Letters, 2014
Physics of the Earth and …, 2003
Geophysical research letters, 2001
Geophysical Research Letters publishes short, concise research letters that present scientific ad... more Geophysical Research Letters publishes short, concise research letters that present scientific advances that are likely to have immediate influence on the research of other investigators. GRL letters can focus on a specific discipline or apply broadly to the geophysical science community ...
Nature, 2003
The tungsten isotope composition of meteorites indicates that core formation in planetesimals occ... more The tungsten isotope composition of meteorites indicates that core formation in planetesimals occurred within a few million years of Solar System formation. But core formation requires a mechanism for segregating metal, and the 'wetting' properties of molten iron alloy in an olivine-rich matrix is thought to preclude segregation by permeable flow unless the silicate itself is partially molten. Excess liquid metal over a percolation threshold, however, can potentially create permeability in a solid matrix, thereby permitting segregation. Here we report the percolation threshold for molten iron-sulphur compounds of approximately 5 vol.% in solid olivine, based on electrical conductivity measurements made in situ at high pressure and temperature. We conclude that heating within planetesimals by decay of short-lived radionuclides can increase temperature sufficiently above the iron-sulphur melting point (approximately 1,000 degrees C) to trigger segregation of iron alloy by permeable flow within the short timeframe indicated by tungsten isotopes. We infer that planetesimals with radii greater than about 30 km and larger planetary embryos are expected to have formed cores very early, and these objects would have contained much of the mass in the terrestrial region of the protoplanetary nebula. The Earth and other terrestrial planets are likely therefore to have formed by accretion of previously differentiated planetesimals, and Earth's core may accordingly be viewed as a blended composite of pre-formed cores.
Science, 1998
convertng to brightness temperatures 27. Bands were formed by summng the observed radiance over a... more convertng to brightness temperatures 27. Bands were formed by summng the observed radiance over a set of TES spectral points. The dust band used 30 points over 889 to 1196 cm-l, the pair of dust continuum bands consisted of elght points at 772 to 846 cm-' and elght points at 1238 to 131 2 cm-' The surface bands were "red"; elght ponts at 360 to 434 cm-I and biue, eight points at 1300 to 1376 cm-'. The atmospheric temperature was estimated by summing two bands on each slde of the 15 p. m CO, band correspondng to a weghtn g functon peaked near 3 mbars 28.
Geophysical research …, 2009
Geophysical research …, 2003
... Atsushi Kubo. Institute for Study of the Earth's Interior, Okayama University, M... more ... Atsushi Kubo. Institute for Study of the Earth's Interior, Okayama University, Misasa, Japan. Eiji Ito. Institute for Study of the Earth's Interior, Okayama University, Misasa, Japan. Tomoo Katsura. Institute for Study of the Earth's Interior, Okayama University, Misasa, Japan. ...
Geophysical Journal …, 2004
Nature, 2008
The Earth's mantle transition zone could potentially store a large amount of water, as the m... more The Earth's mantle transition zone could potentially store a large amount of water, as the minerals wadsleyite and ringwoodite incorporate a significant amount of water in their crystal structure 1, 2 . The water content in the transition zone can be estimated from the electrical ...
Geophysical Research Letters, 1989
The temperature distribution across the transition zone has been determined on the high‐pressure ... more The temperature distribution across the transition zone has been determined on the high‐pressure phase equilibria in the system Mg 2 SiO 4 ‐Fe 2 SiO 4 recently determined by Katsura and Ito [1988] and Ito and Takahashi [1988]. The temperature at the base of the transition zone ...
Applied Magnetic Resonance, 2000
A new unidentified electron center in y-ray-irradiated synthetic stishovite, a high-pressure poly... more A new unidentified electron center in y-ray-irradiated synthetic stishovite, a high-pressure polymorph of SiO,, was detected by X-band electron spin resonance. It has an anisotropic g-factor of orthorhombic symmetry, g, = 1.9764, g 2 = 1.9527 and g3 = 1.9370. The signal intensity was saturated at a microwave power of 2 mW. Annealing experiments show that the center was annealed out around 280 K and unstable at room temperature. The center may be ascribed to a titanium electron center on the basis of a relatively large g-shift and a comparison with the paramagnetic centers in quartz.
The method is described which utilizes slow (10-100 mHz) AC current to determine the electrical c... more The method is described which utilizes slow (10-100 mHz) AC current to determine the electrical conductivity of ferromagnesian minerals at pressures up to 23 GPa and temperatures of 300-2000 K in the 6-8 type multi-anvil highpressure apparatus. The oxidation state of the sample is controlled just below IW buffer. The range of electrical conductivity which can be measured using the present method is 10052-5MS2. An example of measurement was conducted for Mg0.93Fe0.07SiO3 ilmenite. [electrical conductivity, ferromagnesian mineral, oxidation state, high temperature, multi-anvil press]
In this decade, attainable pressure range in a Kawai-type high-pressure apparatus equipped with s... more In this decade, attainable pressure range in a Kawai-type high-pressure apparatus equipped with sintered diamond as second stage anvil is significantly increased and we generated pressure to 97.2 GPa measured by in situ X-ray observation at SPring-8. By using this technique, we measured compressibility of (Fe 0.08 Mg 0.92)SiO 3 perovskite up to more than 90 GPa. The bulk modulus and its pressure derivative are determined to be 268 GPa and 3.8, respectively. These values are slightly different from previous results. However, we obtained consistent results with previous study of bulk modulus of 257 GPa and pressure derivative of 4.3 when we fitted the data in the pressure range less than 70 GPa. The change of compressibility may indicate the spin transition in Fe-bearing perovskite around 70 GPa as suggested by previous study, for example, electrical conductivity measurement, X-ray emission method and so on. [Kawai-type multianvil apparatus, sintered diamond anvil, pressure generation, perovskite, compressibility]
Earth and Planetary Science Letters, 2014
Proceedings of the Japan Academy. Ser. B: Physical and Biological Sciences, 1991
Reaction between molten iron and silicate at high pressure and temperature was examined by employ... more Reaction between molten iron and silicate at high pressure and temperature was examined by employing a mixture of pure iron and (Mg0 9Fe01)2SiO4 olivine as the starting material. The experimental charge quenched at 24 GPa and 2550°C demonstrated that certain amount of Si02 component (at least 2 wt% of Si) dissolved into molten iron from the silicate melt. It is suggested that the dissolving would be enhanced with increasing pressure. The experimental results indicate that Si and 0 are the important alloying light-elements in the earth's core if the core segregation proceeded in the magma ocean of the proto-earth. Concurrently, Si02 contents of the mantle should be substantially reduced from its primitive content.
Physical Review B, 2013
Ferromagnetism in perovskites RTiO 3 can be induced by a steric effect. How the subtle local stru... more Ferromagnetism in perovskites RTiO 3 can be induced by a steric effect. How the subtle local structural change can induce 3D ferromagnetic coupling through Ti-O-Ti superexchange interactions remains controversial. The critical behavior study for the ferromagnetic phase has been made so far only on YTiO 3 since the magnetization measurements are plagued by the contribution from magnetic rare earth. Here we report critical exponents for most ferromagnetic members in the RTiO 3 family by measuring magnetocaloric effect and applying the corresponding scaling laws. Our results indicate that the ferromagnetic coupling in the RTiO 3 can be well-described by the 3D Heisenberg model.
Geophysical Research Letters, 2004
The elastic moduli of polycrystalline wadsleyite, β-(Mg 0.91 Fe 0.09) 2 SiO 4 , were measured up ... more The elastic moduli of polycrystalline wadsleyite, β-(Mg 0.91 Fe 0.09) 2 SiO 4 , were measured up to 470 K by means of the resonant sphere technique. The adiabatic bulk (K S) and shear (µ) moduli were found to be 165.72(6) and 105.43(2) GPa at room temperature. The average slopes (dK S /dT and dµ/dT) in the range were determined to be-0.0175(3) and-0.0159(1) GPa/K. We estimated that the P-, S-wave velocity and density jumps for the αto β-phase transformation at the 410-km depth condition were 9.5, 11.2 and 5.4 %, respectively. These results suggest that the olivine component at the depth should be 52 and 42 volume % for P-and S-waves. 1. Introduction The 410-km discontinuity in the upper mantle is thought to be caused by the transformation of olivine (α-phase) to wadsleyite (β-phase) (Ringwood, 1975). Pyroxene may transform to garnet phase [cf. Irifune and Isshiki, 1998]. But this may affect slopes of velocities and may be excluded in discussion based on the discontinuous change. Comparing the velocity
Geophysical Journal International, 1995
Thermal diffusivity of olivine with (Mg,) xsFeo , I)2Si04 composition is measured at pressures up... more Thermal diffusivity of olivine with (Mg,) xsFeo , I)2Si04 composition is measured at pressures up to 9 GPa and temperatures up to 1700 K using the Angstrom method in a cylindrical geometry. The experimental results demonstrate that lattice thermal diffusivity increases with increasing pressure at a small rate: 46 per cent increase over 10 GPa. The experimental data also suggest that radiative thermal diffusivity may decrease with increasing pressure. Thermal diffusivity in the upper mantle has almost constant values of 7-8 X
Earth and Planetary Science Letters, 2014
Physics of the Earth and …, 2003
Geophysical research letters, 2001
Geophysical Research Letters publishes short, concise research letters that present scientific ad... more Geophysical Research Letters publishes short, concise research letters that present scientific advances that are likely to have immediate influence on the research of other investigators. GRL letters can focus on a specific discipline or apply broadly to the geophysical science community ...
Nature, 2003
The tungsten isotope composition of meteorites indicates that core formation in planetesimals occ... more The tungsten isotope composition of meteorites indicates that core formation in planetesimals occurred within a few million years of Solar System formation. But core formation requires a mechanism for segregating metal, and the 'wetting' properties of molten iron alloy in an olivine-rich matrix is thought to preclude segregation by permeable flow unless the silicate itself is partially molten. Excess liquid metal over a percolation threshold, however, can potentially create permeability in a solid matrix, thereby permitting segregation. Here we report the percolation threshold for molten iron-sulphur compounds of approximately 5 vol.% in solid olivine, based on electrical conductivity measurements made in situ at high pressure and temperature. We conclude that heating within planetesimals by decay of short-lived radionuclides can increase temperature sufficiently above the iron-sulphur melting point (approximately 1,000 degrees C) to trigger segregation of iron alloy by permeable flow within the short timeframe indicated by tungsten isotopes. We infer that planetesimals with radii greater than about 30 km and larger planetary embryos are expected to have formed cores very early, and these objects would have contained much of the mass in the terrestrial region of the protoplanetary nebula. The Earth and other terrestrial planets are likely therefore to have formed by accretion of previously differentiated planetesimals, and Earth's core may accordingly be viewed as a blended composite of pre-formed cores.
Science, 1998
convertng to brightness temperatures 27. Bands were formed by summng the observed radiance over a... more convertng to brightness temperatures 27. Bands were formed by summng the observed radiance over a set of TES spectral points. The dust band used 30 points over 889 to 1196 cm-l, the pair of dust continuum bands consisted of elght points at 772 to 846 cm-' and elght points at 1238 to 131 2 cm-' The surface bands were "red"; elght ponts at 360 to 434 cm-I and biue, eight points at 1300 to 1376 cm-'. The atmospheric temperature was estimated by summing two bands on each slde of the 15 p. m CO, band correspondng to a weghtn g functon peaked near 3 mbars 28.
Geophysical research …, 2009
Geophysical research …, 2003
... Atsushi Kubo. Institute for Study of the Earth's Interior, Okayama University, M... more ... Atsushi Kubo. Institute for Study of the Earth's Interior, Okayama University, Misasa, Japan. Eiji Ito. Institute for Study of the Earth's Interior, Okayama University, Misasa, Japan. Tomoo Katsura. Institute for Study of the Earth's Interior, Okayama University, Misasa, Japan. ...
Geophysical Journal …, 2004
Nature, 2008
The Earth's mantle transition zone could potentially store a large amount of water, as the m... more The Earth's mantle transition zone could potentially store a large amount of water, as the minerals wadsleyite and ringwoodite incorporate a significant amount of water in their crystal structure 1, 2 . The water content in the transition zone can be estimated from the electrical ...
Geophysical Research Letters, 1989
The temperature distribution across the transition zone has been determined on the high‐pressure ... more The temperature distribution across the transition zone has been determined on the high‐pressure phase equilibria in the system Mg 2 SiO 4 ‐Fe 2 SiO 4 recently determined by Katsura and Ito [1988] and Ito and Takahashi [1988]. The temperature at the base of the transition zone ...
Applied Magnetic Resonance, 2000
A new unidentified electron center in y-ray-irradiated synthetic stishovite, a high-pressure poly... more A new unidentified electron center in y-ray-irradiated synthetic stishovite, a high-pressure polymorph of SiO,, was detected by X-band electron spin resonance. It has an anisotropic g-factor of orthorhombic symmetry, g, = 1.9764, g 2 = 1.9527 and g3 = 1.9370. The signal intensity was saturated at a microwave power of 2 mW. Annealing experiments show that the center was annealed out around 280 K and unstable at room temperature. The center may be ascribed to a titanium electron center on the basis of a relatively large g-shift and a comparison with the paramagnetic centers in quartz.