Jesus Gonzalez - Academia.edu (original) (raw)
Papers by Jesus Gonzalez
Journal of Alloys and Compounds, 2010
Nanocrystalline Fe75Si15B10 powders were obtained by mechanical alloying in a high energy planeta... more Nanocrystalline Fe75Si15B10 powders were obtained by mechanical alloying in a high energy planetary ball mill. Morphological, microstructural, structural and magnetic property changes during the milling process were followed by scanning electron microscopy, X-ray diffraction and magnetic measurements. The crystallite size reduction to the nanometer scale (6–13nm) is accompanied by an increase in atomic level strain. The Fe2B boride phase is
Physical Review B, 2008
High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitte... more High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitted to hydrostatic pressure up to 10 GPa. A specific setup with a miniature diamond-anvil cell has been developed to combine high pressure and pulsed magnetic fields and to perform magnetophotoluminescence measurements. Careful analysis of low-temperature ͑4.2 and 77 K͒ photoluminescence spectra with a 56 T magnetic field applied along the c axis allows for the rectification of the assignment of observed emission lines to corresponding Zeeman-split levels. Besides, the intrinsic Zeeman-splitting factors of excited states reveal a linear pressure-induced increase. This enhancement is a signature of an increase in trigonal distortion induced by hydrostatic pressure. Moreover, spectra with magnetic field perpendicular to crystallographic c axis exhibit a Paschen-Back effect reflecting the progressive alignment of Cr 3+ ions spin along the applied field. However, no pressure modification is observed in this compound, contrarily to the Heisenberg-to-Ising spin character pressure-induced transition observed in alexandrite.
Physical Review B, 2010
We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuprosc... more We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuproscheelite. We performed powder x-ray diffraction and Raman spectroscopy experiments up to 27 GPa as well as ab initio total-energy and latticedynamics calculations. Experiments provide evidence that a structural phase transition takes place at 10 GPa from the low-pressure triclinic phase (P1) to a monoclinic
Nano Letters, 2016
This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nan... more This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nanoparticles (NPs) by means of optical measurements under pressure (up to 25 GPa), X-ray absorption and Transmission Electron Microscopy. W-NPs were chemically synthesized at ambient conditions and RS-NPs were obtained by pressure-induced transformation of W-NPs. In contrast to the abrupt phase transition in W-Zn1-xCoxO as thin film or single crystal, occurring sharply at about 9 GPa, spectroscopic signatures of tetrahedral Co2+ are observed in NPs from ambient pressure to about 17 GPa. Above this pressure, several changes in the absorption spectrum reveal a gradual and irreversible W-to-RS phase transition: i) the fundamental band-to-band edge shifts to higher photon energies; ii) the charge-transfer absorption band virtually disappears (or overlaps the fundamental edge); and iii) the intensity of the crystal-field absorption peaks of Co2+ around 2 eV decreases by an order of magnitude and shifts to 2.5 eV. After incomplete phase transition pressure cycles, the absorption edge of non-transformed W-NPs, at ambient pressure, exhibits a blue-shift of 0.22 eV. This extra shift is interpreted in terms of quantum confinement effects. The observed gradual phase transition and metastability are related to the NP size distribution: the larger the NP the lower the W-to-RS transition pressure.
Hyperfine Interactions, 1998
The Mssbauer measurements at variable temperature (from liquid helium to room temperature) on the... more The Mssbauer measurements at variable temperature (from liquid helium to room temperature) on the layered compound CuFeTe2 have been able to determine the existence of a magnetically ordered state below T N= 254 15 K. The general shape of the spectra and the magnitudes of the hyperfine fields let us to propose a Spin Density Wave (SDW) behavior for this
Il Nuovo Cimento D, 1983
... (hv-E~)~ at hv > 0.95 eV, indicating direct energy gaps at both 100 and 300 K (see fig. 1)... more ... (hv-E~)~ at hv > 0.95 eV, indicating direct energy gaps at both 100 and 300 K (see fig. 1). However, for hv < 0.95 eV ~ does not obey this relation, indicating an additional absorption mechanism. ... 1898 c. RINCdN, J. GONZALEZ, G. SANCHEZ P~REZ and c. BELLABARBA 16 '12 ...
Advances in Materials Physics and Chemistry, 2013
The electronic structure, band gap, density of states of the (8,8), (14,0) and (12,3) single-wall... more The electronic structure, band gap, density of states of the (8,8), (14,0) and (12,3) single-walled carbon nanotubes by the SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) method in the framework density-functional theory (DFT) with the generalized gradients approximation (GGA) were studied. Also, we studied the vibrational properties of the (8,8) and (14,0) nanotubes. Only the calculated relaxed geometry for (12,3) nanotube show significant deviations from the ideal rolled graphene sheet configuration. The electronic transition energies of van Hove singularities were studied and compared with previous results. The calculated band structures, density of states and dispersion curves for all tubes were in good agreement with theoretical and experimental results.
physica status solidi (b), 1983
Solar Cells, 1986
The dependence of the bandgap in CuInSe2 on temperature is explained by a model which takes into ... more The dependence of the bandgap in CuInSe2 on temperature is explained by a model which takes into account the contribution of all the vibrational modes in the electron-phonon interaction.
Physical Chemistry Chemical Physics, 2013
A novel organic ionic plastic crystal (OIPC) based on a quaternary ammonium cation and a tetrachl... more A novel organic ionic plastic crystal (OIPC) based on a quaternary ammonium cation and a tetrachloroferrate anion has been synthesized with the intention of combining the properties of the ionic plastic crystal and the magnetism originating from the iron incorporated in the anion. The thermal analysis of the obtained OIPC showed a solid-solid phase transition below room temperature and a high melting point above 220 °C, indicating their plastic crystalline behaviour over a wide temperature range, as well as thermal stability up to approximately 200 °C. The magnetization measurements show the presence of three-dimensional antiferromagnetic ordering below 4 K. The results from electrochemical characterization display a solid-state ionic conduction sufficiently high and stable (between 10(-2.7) and 10(-3.6) S cm(-1) from 20 to 180 °C) for electrochemical applications.
physica status solidi (b), 2004
Polycrystalline samples of (CuInSe2)1-x(CoSe)x alloys were prepared by the normal melt and anneal... more Polycrystalline samples of (CuInSe2)1-x(CoSe)x alloys were prepared by the normal melt and anneal technique in the composition range 0 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; x 2/3. The obtained ingots were characterized by scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. A sample with x = 2/3 (prepared a posteriori) was also studied by the Raman shift technique. The results showed a complex
physica status solidi (b), 1983
... However, for hv 6 0.98 eV, OL does not obey this relation, indicating the presence of an ad-d... more ... However, for hv 6 0.98 eV, OL does not obey this relation, indicating the presence of an ad-ditional absorption mechanism different from the impurity absorption mechanism observed at 10 K in CuInSe2, which has been reported elsewhere ... lo/ C. FUNCbN, J. GONZALEZ, andG. ...
physica status solidi (b), 2013
Physica B: Condensed Matter, 2001
Measurements of magnetization (M) at helium temperatures and with pulsed magnetic fields up to 32... more Measurements of magnetization (M) at helium temperatures and with pulsed magnetic fields up to 32T, have been made on polycrystalline samples of the three compounds Ag2FeGeSe4, Ag2FeSiSe4 and Cu2MnGeSe4. All three compounds have orthorhombic symmetry, with the wurtz–stannite structure, and have semiconductor properties. The resulting curves of M versus B have been used to give information on the magnetic spin–flop
Nano Letters, 2008
OATAO is an open access repository that collects the work of Toulouse researchers and makes it fr... more OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.
Journal of Electronic Materials, 1993
The T(z) diagram of the system Cd1−zMnzGa2Se4 was obtained from x-ray diffraction and differentia... more The T(z) diagram of the system Cd1−zMnzGa2Se4 was obtained from x-ray diffraction and differential thermal analysis measurements. It was found that at lower temperatures, a single phase solid solution occurs across the whole compositional range and values of lattice parameters were determined as a function of z. At higher temperatures, an order-disorder transition occurs, in the range 0 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; z
Journal of Alloys and Compounds, 2010
Nanocrystalline Fe75Si15B10 powders were obtained by mechanical alloying in a high energy planeta... more Nanocrystalline Fe75Si15B10 powders were obtained by mechanical alloying in a high energy planetary ball mill. Morphological, microstructural, structural and magnetic property changes during the milling process were followed by scanning electron microscopy, X-ray diffraction and magnetic measurements. The crystallite size reduction to the nanometer scale (6–13nm) is accompanied by an increase in atomic level strain. The Fe2B boride phase is
Physical Review B, 2008
High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitte... more High-field Zeeman and Paschen-Back effects have been observed in single crystals of ruby submitted to hydrostatic pressure up to 10 GPa. A specific setup with a miniature diamond-anvil cell has been developed to combine high pressure and pulsed magnetic fields and to perform magnetophotoluminescence measurements. Careful analysis of low-temperature ͑4.2 and 77 K͒ photoluminescence spectra with a 56 T magnetic field applied along the c axis allows for the rectification of the assignment of observed emission lines to corresponding Zeeman-split levels. Besides, the intrinsic Zeeman-splitting factors of excited states reveal a linear pressure-induced increase. This enhancement is a signature of an increase in trigonal distortion induced by hydrostatic pressure. Moreover, spectra with magnetic field perpendicular to crystallographic c axis exhibit a Paschen-Back effect reflecting the progressive alignment of Cr 3+ ions spin along the applied field. However, no pressure modification is observed in this compound, contrarily to the Heisenberg-to-Ising spin character pressure-induced transition observed in alexandrite.
Physical Review B, 2010
We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuprosc... more We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuproscheelite. We performed powder x-ray diffraction and Raman spectroscopy experiments up to 27 GPa as well as ab initio total-energy and latticedynamics calculations. Experiments provide evidence that a structural phase transition takes place at 10 GPa from the low-pressure triclinic phase (P1) to a monoclinic
Nano Letters, 2016
This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nan... more This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nanoparticles (NPs) by means of optical measurements under pressure (up to 25 GPa), X-ray absorption and Transmission Electron Microscopy. W-NPs were chemically synthesized at ambient conditions and RS-NPs were obtained by pressure-induced transformation of W-NPs. In contrast to the abrupt phase transition in W-Zn1-xCoxO as thin film or single crystal, occurring sharply at about 9 GPa, spectroscopic signatures of tetrahedral Co2+ are observed in NPs from ambient pressure to about 17 GPa. Above this pressure, several changes in the absorption spectrum reveal a gradual and irreversible W-to-RS phase transition: i) the fundamental band-to-band edge shifts to higher photon energies; ii) the charge-transfer absorption band virtually disappears (or overlaps the fundamental edge); and iii) the intensity of the crystal-field absorption peaks of Co2+ around 2 eV decreases by an order of magnitude and shifts to 2.5 eV. After incomplete phase transition pressure cycles, the absorption edge of non-transformed W-NPs, at ambient pressure, exhibits a blue-shift of 0.22 eV. This extra shift is interpreted in terms of quantum confinement effects. The observed gradual phase transition and metastability are related to the NP size distribution: the larger the NP the lower the W-to-RS transition pressure.
Hyperfine Interactions, 1998
The Mssbauer measurements at variable temperature (from liquid helium to room temperature) on the... more The Mssbauer measurements at variable temperature (from liquid helium to room temperature) on the layered compound CuFeTe2 have been able to determine the existence of a magnetically ordered state below T N= 254 15 K. The general shape of the spectra and the magnitudes of the hyperfine fields let us to propose a Spin Density Wave (SDW) behavior for this
Il Nuovo Cimento D, 1983
... (hv-E~)~ at hv > 0.95 eV, indicating direct energy gaps at both 100 and 300 K (see fig. 1)... more ... (hv-E~)~ at hv > 0.95 eV, indicating direct energy gaps at both 100 and 300 K (see fig. 1). However, for hv < 0.95 eV ~ does not obey this relation, indicating an additional absorption mechanism. ... 1898 c. RINCdN, J. GONZALEZ, G. SANCHEZ P~REZ and c. BELLABARBA 16 '12 ...
Advances in Materials Physics and Chemistry, 2013
The electronic structure, band gap, density of states of the (8,8), (14,0) and (12,3) single-wall... more The electronic structure, band gap, density of states of the (8,8), (14,0) and (12,3) single-walled carbon nanotubes by the SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) method in the framework density-functional theory (DFT) with the generalized gradients approximation (GGA) were studied. Also, we studied the vibrational properties of the (8,8) and (14,0) nanotubes. Only the calculated relaxed geometry for (12,3) nanotube show significant deviations from the ideal rolled graphene sheet configuration. The electronic transition energies of van Hove singularities were studied and compared with previous results. The calculated band structures, density of states and dispersion curves for all tubes were in good agreement with theoretical and experimental results.
physica status solidi (b), 1983
Solar Cells, 1986
The dependence of the bandgap in CuInSe2 on temperature is explained by a model which takes into ... more The dependence of the bandgap in CuInSe2 on temperature is explained by a model which takes into account the contribution of all the vibrational modes in the electron-phonon interaction.
Physical Chemistry Chemical Physics, 2013
A novel organic ionic plastic crystal (OIPC) based on a quaternary ammonium cation and a tetrachl... more A novel organic ionic plastic crystal (OIPC) based on a quaternary ammonium cation and a tetrachloroferrate anion has been synthesized with the intention of combining the properties of the ionic plastic crystal and the magnetism originating from the iron incorporated in the anion. The thermal analysis of the obtained OIPC showed a solid-solid phase transition below room temperature and a high melting point above 220 °C, indicating their plastic crystalline behaviour over a wide temperature range, as well as thermal stability up to approximately 200 °C. The magnetization measurements show the presence of three-dimensional antiferromagnetic ordering below 4 K. The results from electrochemical characterization display a solid-state ionic conduction sufficiently high and stable (between 10(-2.7) and 10(-3.6) S cm(-1) from 20 to 180 °C) for electrochemical applications.
physica status solidi (b), 2004
Polycrystalline samples of (CuInSe2)1-x(CoSe)x alloys were prepared by the normal melt and anneal... more Polycrystalline samples of (CuInSe2)1-x(CoSe)x alloys were prepared by the normal melt and anneal technique in the composition range 0 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; x 2/3. The obtained ingots were characterized by scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. A sample with x = 2/3 (prepared a posteriori) was also studied by the Raman shift technique. The results showed a complex
physica status solidi (b), 1983
... However, for hv 6 0.98 eV, OL does not obey this relation, indicating the presence of an ad-d... more ... However, for hv 6 0.98 eV, OL does not obey this relation, indicating the presence of an ad-ditional absorption mechanism different from the impurity absorption mechanism observed at 10 K in CuInSe2, which has been reported elsewhere ... lo/ C. FUNCbN, J. GONZALEZ, andG. ...
physica status solidi (b), 2013
Physica B: Condensed Matter, 2001
Measurements of magnetization (M) at helium temperatures and with pulsed magnetic fields up to 32... more Measurements of magnetization (M) at helium temperatures and with pulsed magnetic fields up to 32T, have been made on polycrystalline samples of the three compounds Ag2FeGeSe4, Ag2FeSiSe4 and Cu2MnGeSe4. All three compounds have orthorhombic symmetry, with the wurtz–stannite structure, and have semiconductor properties. The resulting curves of M versus B have been used to give information on the magnetic spin–flop
Nano Letters, 2008
OATAO is an open access repository that collects the work of Toulouse researchers and makes it fr... more OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.
Journal of Electronic Materials, 1993
The T(z) diagram of the system Cd1−zMnzGa2Se4 was obtained from x-ray diffraction and differentia... more The T(z) diagram of the system Cd1−zMnzGa2Se4 was obtained from x-ray diffraction and differential thermal analysis measurements. It was found that at lower temperatures, a single phase solid solution occurs across the whole compositional range and values of lattice parameters were determined as a function of z. At higher temperatures, an order-disorder transition occurs, in the range 0 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; z