Juan Bartolome | University of Zaragoza (original) (raw)
Papers by Juan Bartolome
Dalton Transactions
The thermal expansion affects the electronic state of Co3+ ions triggering the spin-state crossov... more The thermal expansion affects the electronic state of Co3+ ions triggering the spin-state crossover and following the charge-ordering transition without changing the symmetry.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Iron phthalocyanines (FePc) adsorbed onto a Ag(110) substrate self-assemble into different monola... more Iron phthalocyanines (FePc) adsorbed onto a Ag(110) substrate self-assemble into different monolayer phases going from rectangular to different oblique phases, with increasing molecular density. We...
Journal of Magnetism and Magnetic Materials, 2007
ABSTRACT Co-doped indium–tin oxide (ITO) films were produced by magnetron sputtering on fused qua... more ABSTRACT Co-doped indium–tin oxide (ITO) films were produced by magnetron sputtering on fused quartz substrates under various conditions. We find that post-growth processing of films affects crucially their electronic and magnetic properties. Films with 30 at% of Co show hysteretic magnetization and anomalous Hall effect up to room temperature. Values of up to per Co atom are obtained for the saturation magnetic moment in these films. A mixed magnetic state with Co-rich ITO or Co-metal nanoclusters within a homogeneous ITO:Co matrix might give rise to such behavior.
Journal of Magnetism and Magnetic Materials, 1996
The frequency and temperature dependence of the ac susceptibility between 1.8 and 350 K in a frO ... more The frequency and temperature dependence of the ac susceptibility between 1.8 and 350 K in a frO 2 DCC magnetic tape has been measured. The in-phase (X') component of the susceptibility has a logarithmic frequency dependence which can be associated with the presence of magnetic particles which block below room temperature. The out-of-phase component (X") and dx'/d(ln(to) decrease below 3 K indicating that the magnetic moment of these particles rotates by thermal activation.
Journal of Magnetism and Magnetic Materials, 1995
Experimental results for the temperature dependence of susceptibility and specific heat of microc... more Experimental results for the temperature dependence of susceptibility and specific heat of microcrystalline Gd(hfac)3NITEt are presented. The data are compared with transfer matrix calculations, in a one-dimensional classical planar model with competing nearest- and next-nearest-neighbour exchange interactions, leading to helical spin arrangement with chiral degeneracy. A peak at T = 2 T in the T-dependence of the specific heat is
IEEE Transactions on Magnetics, 1994
The anomaly detected in the magnetic AC susceptibility of many intermetallic compounds between 10... more The anomaly detected in the magnetic AC susceptibility of many intermetallic compounds between 100 and 300 K, and in particular in Nd 2Fe14B at 220 K, has been induced in a controlled manner by thermal annealing. The anomaly has been interpreted in terms of thermal activated processes of defects imposing their dynamical behavior on the domain walls coupled to them, thus solving the controversy on its origin
IEEE Transactions on Magnetics, 2008
We present a study of the magnetic properties and the 57Fe Mossbauer spectra of the Hf1-x R xFe6G... more We present a study of the magnetic properties and the 57Fe Mossbauer spectra of the Hf1-x R xFe6Ge6, R = Gd and Dy, series. The macroscopic magnetic measurements are consistent with the magnetic independence of the R and Fe sublattices. However, the 57Fe Mossbauer study reveals a more complex magnetic behavior. Specifically, below T t ap 100 K a spin reorientation takes place in HfFe6 Ge6 . The analysis of the corresponding Mossbauer spectra shows that below T t a fraction of the iron moments is canted from the c-axis. The substitution of Hf by Gd or Dy reduces the fraction of canted iron moments. The hyperfine magnetic fields are found to decrease upon the R = Gd or Dy substitution. This effect can be qualitatively explained as a result of the decrease in the hybridization between the d valence states of the R element with the 3d iron states.
Journal of Magnetism and Magnetic Materials, 1992
... ed. LV. Mitchell (Elsevier Applied Science, Barking, 1989) p. 240. [10] C. Rillo, F. Lera, A.... more ... ed. LV. Mitchell (Elsevier Applied Science, Barking, 1989) p. 240. [10] C. Rillo, F. Lera, A. Badia, LA Angurel, J. Bartolom , F. Palacio, R. Navarro and AJ. van Duyneveldt, in: Magnetic Susceptibility of Superconductors and Other Spin Systems, eds. ...
Journal of Magnetism and Magnetic Materials, 2015
Magnetic properties of heterometallic warwickites MgFeBO 4, Mg 0.5 Co 0.5 FeBO 4, and CoFeBO 4 ar... more Magnetic properties of heterometallic warwickites MgFeBO 4, Mg 0.5 Co 0.5 FeBO 4, and CoFeBO 4 are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below T SG ¼10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above T SG show quantum entanglement behavior χ(Τ)∝T À α(Τ) up to T E E 130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above T E the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie-Weiss paramagnetism. The different intra-and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite structure, together with the competing interactions, induce frustration. The spin-glass character is explained in terms of the substitutional disorder of the Mg, Fe and Co atoms at the two available crystallographic sites, and the frustration induced by the competing interactions. The Co substitution induces uniaxial anisotropy, increases the absolute magnetization and increases the spin-glass freezing temperature. The entanglement behavior is supported in the intermediate phase irrespective of the introduction of anisotropy by the Co substitution. & 2015 Elsevier B.V. All rights reserved. warwickites with only one magnetic ion, MgTiBO 4 [9-11], MgCrBO 4 [12], MgFeBO 4 [12,13], NiScBO 4 [12], MnScBO 4 [12], MgVBO 4 [12,14]. At sufficiently high temperature, heterometallic warwickites with just one magnetic metal are paramagnetic and obey the Curie-Weiss law with antiferromagnetic exchange interaction between nearest neighbors. As temperature is lowered, short range interaction within the ribbons gives rise to quasi one-dimensional interactions since k B T becomes of the order of the intraribbon exchange energy. In this temperature range these materials Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials
Magnetic properties of heterometallic warwickites MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 are prese... more Magnetic properties of heterometallic warwickites MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below TSG=10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above TSG show quantum entanglement behavior χ(Τ)∝T−α(Τ) up to TE≈130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above TE the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie–Weiss paramagnetism. The different intra- and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite...
IEEE Transactions on Magnetics, 1994
Heat capacity of the perovskite NdGaO3 has been measured in the range of 0.15 K<T&... more Heat capacity of the perovskite NdGaO3 has been measured in the range of 0.15 K<T<3 K showing an anomaly that is interpreted as ordering of the Nd3+ ions at Tc=0.97±0.01 K. This is, to our knowledge, the best example of a 3D XY magnetic ordering in a rare earth system, free from any other contribution, and the first such example
The compounds Gd2(ox)[Cu(pba)]3[Cu(H2O)5] · 20H2O (1) and Gd2[Cu(opba)]3 · 6DMSO · 4H2O (2) are s... more The compounds Gd2(ox)[Cu(pba)]3[Cu(H2O)5] · 20H2O (1) and Gd2[Cu(opba)]3 · 6DMSO · 4H2O (2) are spin ladder-based molecular ferromagnets. Low-temperature specific heat measurements show that both compounds undergo three-dimensional magnetic ordering with Tc = 1.05 K for (1) and Tc = 1.78 K for (2). These materials represent the unique examples of long-range ordering, reported so far, for gadolinium and copper-based
The Journal of Chemical Thermodynamics
Nature communications, Mar 29, 2018
Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal i... more Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal in the design of new molecules with evermore realizable applications in spin-based devices. For single-ion lanthanide systems, with strong spin-orbit coupling, the potential applications are linked to the energetic structure of the crystal field levels and quantum tunneling within the ground state. Structural engineering of the timescale of these tunneling events via appropriate design of crystal fields represents a fundamental challenge for the synthetic chemist, since tunnel splittings are expected to be suppressed by crystal field environments with sufficiently high-order symmetry. Here, we report the long missing study of the effect of a non-linear (C) to pseudo-linear (D) change in crystal field symmetry in an otherwise chemically unaltered dysprosium complex. From a purely experimental study of crystal field levels and electronic spin dynamics at milliKelvin temperatures, we demonst...
Dalton Trans., 2017
A large single-ion transverse anisotropy at Mn(iii) sites induces slow magnetic relaxation at zer... more A large single-ion transverse anisotropy at Mn(iii) sites induces slow magnetic relaxation at zero magnetic field of the ferromagnetic Mn dimers in a singular Mn2Ca2 complex.
J Magn Magn Mater, 1995
ABSTRACT
Dalton Transactions
The thermal expansion affects the electronic state of Co3+ ions triggering the spin-state crossov... more The thermal expansion affects the electronic state of Co3+ ions triggering the spin-state crossover and following the charge-ordering transition without changing the symmetry.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Iron phthalocyanines (FePc) adsorbed onto a Ag(110) substrate self-assemble into different monola... more Iron phthalocyanines (FePc) adsorbed onto a Ag(110) substrate self-assemble into different monolayer phases going from rectangular to different oblique phases, with increasing molecular density. We...
Journal of Magnetism and Magnetic Materials, 2007
ABSTRACT Co-doped indium–tin oxide (ITO) films were produced by magnetron sputtering on fused qua... more ABSTRACT Co-doped indium–tin oxide (ITO) films were produced by magnetron sputtering on fused quartz substrates under various conditions. We find that post-growth processing of films affects crucially their electronic and magnetic properties. Films with 30 at% of Co show hysteretic magnetization and anomalous Hall effect up to room temperature. Values of up to per Co atom are obtained for the saturation magnetic moment in these films. A mixed magnetic state with Co-rich ITO or Co-metal nanoclusters within a homogeneous ITO:Co matrix might give rise to such behavior.
Journal of Magnetism and Magnetic Materials, 1996
The frequency and temperature dependence of the ac susceptibility between 1.8 and 350 K in a frO ... more The frequency and temperature dependence of the ac susceptibility between 1.8 and 350 K in a frO 2 DCC magnetic tape has been measured. The in-phase (X') component of the susceptibility has a logarithmic frequency dependence which can be associated with the presence of magnetic particles which block below room temperature. The out-of-phase component (X") and dx'/d(ln(to) decrease below 3 K indicating that the magnetic moment of these particles rotates by thermal activation.
Journal of Magnetism and Magnetic Materials, 1995
Experimental results for the temperature dependence of susceptibility and specific heat of microc... more Experimental results for the temperature dependence of susceptibility and specific heat of microcrystalline Gd(hfac)3NITEt are presented. The data are compared with transfer matrix calculations, in a one-dimensional classical planar model with competing nearest- and next-nearest-neighbour exchange interactions, leading to helical spin arrangement with chiral degeneracy. A peak at T = 2 T in the T-dependence of the specific heat is
IEEE Transactions on Magnetics, 1994
The anomaly detected in the magnetic AC susceptibility of many intermetallic compounds between 10... more The anomaly detected in the magnetic AC susceptibility of many intermetallic compounds between 100 and 300 K, and in particular in Nd 2Fe14B at 220 K, has been induced in a controlled manner by thermal annealing. The anomaly has been interpreted in terms of thermal activated processes of defects imposing their dynamical behavior on the domain walls coupled to them, thus solving the controversy on its origin
IEEE Transactions on Magnetics, 2008
We present a study of the magnetic properties and the 57Fe Mossbauer spectra of the Hf1-x R xFe6G... more We present a study of the magnetic properties and the 57Fe Mossbauer spectra of the Hf1-x R xFe6Ge6, R = Gd and Dy, series. The macroscopic magnetic measurements are consistent with the magnetic independence of the R and Fe sublattices. However, the 57Fe Mossbauer study reveals a more complex magnetic behavior. Specifically, below T t ap 100 K a spin reorientation takes place in HfFe6 Ge6 . The analysis of the corresponding Mossbauer spectra shows that below T t a fraction of the iron moments is canted from the c-axis. The substitution of Hf by Gd or Dy reduces the fraction of canted iron moments. The hyperfine magnetic fields are found to decrease upon the R = Gd or Dy substitution. This effect can be qualitatively explained as a result of the decrease in the hybridization between the d valence states of the R element with the 3d iron states.
Journal of Magnetism and Magnetic Materials, 1992
... ed. LV. Mitchell (Elsevier Applied Science, Barking, 1989) p. 240. [10] C. Rillo, F. Lera, A.... more ... ed. LV. Mitchell (Elsevier Applied Science, Barking, 1989) p. 240. [10] C. Rillo, F. Lera, A. Badia, LA Angurel, J. Bartolom , F. Palacio, R. Navarro and AJ. van Duyneveldt, in: Magnetic Susceptibility of Superconductors and Other Spin Systems, eds. ...
Journal of Magnetism and Magnetic Materials, 2015
Magnetic properties of heterometallic warwickites MgFeBO 4, Mg 0.5 Co 0.5 FeBO 4, and CoFeBO 4 ar... more Magnetic properties of heterometallic warwickites MgFeBO 4, Mg 0.5 Co 0.5 FeBO 4, and CoFeBO 4 are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below T SG ¼10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above T SG show quantum entanglement behavior χ(Τ)∝T À α(Τ) up to T E E 130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above T E the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie-Weiss paramagnetism. The different intra-and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite structure, together with the competing interactions, induce frustration. The spin-glass character is explained in terms of the substitutional disorder of the Mg, Fe and Co atoms at the two available crystallographic sites, and the frustration induced by the competing interactions. The Co substitution induces uniaxial anisotropy, increases the absolute magnetization and increases the spin-glass freezing temperature. The entanglement behavior is supported in the intermediate phase irrespective of the introduction of anisotropy by the Co substitution. & 2015 Elsevier B.V. All rights reserved. warwickites with only one magnetic ion, MgTiBO 4 [9-11], MgCrBO 4 [12], MgFeBO 4 [12,13], NiScBO 4 [12], MnScBO 4 [12], MgVBO 4 [12,14]. At sufficiently high temperature, heterometallic warwickites with just one magnetic metal are paramagnetic and obey the Curie-Weiss law with antiferromagnetic exchange interaction between nearest neighbors. As temperature is lowered, short range interaction within the ribbons gives rise to quasi one-dimensional interactions since k B T becomes of the order of the intraribbon exchange energy. In this temperature range these materials Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials
Magnetic properties of heterometallic warwickites MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 are prese... more Magnetic properties of heterometallic warwickites MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below TSG=10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above TSG show quantum entanglement behavior χ(Τ)∝T−α(Τ) up to TE≈130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above TE the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie–Weiss paramagnetism. The different intra- and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite...
IEEE Transactions on Magnetics, 1994
Heat capacity of the perovskite NdGaO3 has been measured in the range of 0.15 K<T&... more Heat capacity of the perovskite NdGaO3 has been measured in the range of 0.15 K<T<3 K showing an anomaly that is interpreted as ordering of the Nd3+ ions at Tc=0.97±0.01 K. This is, to our knowledge, the best example of a 3D XY magnetic ordering in a rare earth system, free from any other contribution, and the first such example
The compounds Gd2(ox)[Cu(pba)]3[Cu(H2O)5] · 20H2O (1) and Gd2[Cu(opba)]3 · 6DMSO · 4H2O (2) are s... more The compounds Gd2(ox)[Cu(pba)]3[Cu(H2O)5] · 20H2O (1) and Gd2[Cu(opba)]3 · 6DMSO · 4H2O (2) are spin ladder-based molecular ferromagnets. Low-temperature specific heat measurements show that both compounds undergo three-dimensional magnetic ordering with Tc = 1.05 K for (1) and Tc = 1.78 K for (2). These materials represent the unique examples of long-range ordering, reported so far, for gadolinium and copper-based
The Journal of Chemical Thermodynamics
Nature communications, Mar 29, 2018
Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal i... more Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal in the design of new molecules with evermore realizable applications in spin-based devices. For single-ion lanthanide systems, with strong spin-orbit coupling, the potential applications are linked to the energetic structure of the crystal field levels and quantum tunneling within the ground state. Structural engineering of the timescale of these tunneling events via appropriate design of crystal fields represents a fundamental challenge for the synthetic chemist, since tunnel splittings are expected to be suppressed by crystal field environments with sufficiently high-order symmetry. Here, we report the long missing study of the effect of a non-linear (C) to pseudo-linear (D) change in crystal field symmetry in an otherwise chemically unaltered dysprosium complex. From a purely experimental study of crystal field levels and electronic spin dynamics at milliKelvin temperatures, we demonst...
Dalton Trans., 2017
A large single-ion transverse anisotropy at Mn(iii) sites induces slow magnetic relaxation at zer... more A large single-ion transverse anisotropy at Mn(iii) sites induces slow magnetic relaxation at zero magnetic field of the ferromagnetic Mn dimers in a singular Mn2Ca2 complex.
J Magn Magn Mater, 1995
ABSTRACT