E. Burzo | Babes-Bolyai University (original) (raw)
Papers by E. Burzo
Journal of Alloys and Compounds
The Sr2FeMo1-xMxO6 double perovskites with M = W and Ta and x <= 0.3, were obtained by sinteri... more The Sr2FeMo1-xMxO6 double perovskites with M = W and Ta and x <= 0.3, were obtained by sintering at 1300 degrees C. during 4 and 8 h, respectively. The perovskites crystallize in a tetragonal structure having 14/mmm space group. The grains are more homogeneous when sintering time is increased. The samples sintered longer time show higher values of saturation magnetizations, resistivities and magnetoresistivities than the samples sintered during 4 h. The intergrain tunnelling magnetoresistance as well as the intragrain contributions, respectively were analysed as function of temperature and external field. The changes in the physical properties, when the sintering time is increased, have been correlated with the number of antisite defects as well as the nature of grain boundaries. (C) 2010 Elsevier B.V. All rights reserved.
physica status solidi (c), 2004
ABSTRACT The GdxY1–xCo3NiB compounds form solid solutions in all the composition range having hex... more ABSTRACT The GdxY1–xCo3NiB compounds form solid solutions in all the composition range having hexagonal CeCo4B-type structure. The saturation magnetizations, at 4.2 K, decrease from 4.56 μB/f.u. (x = 1) up to a composition x = 0.275, when the resultant moment is nil and then increase up to 1.7 μB/fu for YCo3NiB.This behaviour is in agreement with a ferrimagnetic type ordering. The magnetic moments at various sites are analysed in correlation with their local environments. A magnetic moment is induced on Ni atoms. The mean effective cobalt and nickel moments seem to be little dependent on composition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic measurements and XPS studies were performed on LaNi5-xAlx, TbNi5-xAlx, DyNi5-xAlx, LaNi5... more Magnetic measurements and XPS studies were performed on LaNi5-xAlx, TbNi5-xAlx, DyNi5-xAlx, LaNi5-xCux and NdNi5-xCux systems. In addition, band structure calculations were also performed. The nickel moments in RNi5 (R=Nd, Tb, Dy) compounds are of ≅ 0.17 µ B and ≅ 0.25 µ B at 2c and 3g sites, respectively. The nickel moments, in low temperature range, decrease when increasing Al or Cu content and are practically nil for x > 1. The 4f-5d-3d exchange interactions were analyzed and the contributions of local 4f-5d and short range 5d-3d exchange interactions to 5d band polarization are estimated. An effective field of the order of (30-40) T is necessary to induce a nickel moment, at 1.7 K. Above the Curie temperatures, the effective nickel moments were determined. The LaNi5-xCux and LaNi5-xAlx systems, show, at T ≤ 10 K, a T2 dependence of the magnetic susceptibilities, while above a characteristic temperature T*, a Curie-Weiss contribution was evidenced. The magnetic behaviour of ni...
Journal of Magnetism and Magnetic Materials, 2010
The magnetic and electrical properties of polycrystalline Pr 1Àx A x CoO 3 cobaltites with A ¼ Ca... more The magnetic and electrical properties of polycrystalline Pr 1Àx A x CoO 3 cobaltites with A ¼ Ca, Sr and 0rxr0.5 were studied in the temperature range 4 KrTr1000 K and field up to 7 T. The X-ray analyses show the presence of only one phase having monoclinic or orthorhombic symmetry. The magnetic measurements indicate that the Ca-doped samples have at low temperatures, similar properties to the frustrated magnetic materials. PrCoO 3 is a paramagnetic insulator in the range from 4 to 1000 K. The Srdoped cobaltites exhibit two phase transitions: a paramagnetic-ferromagnetic (or magnetic phase separated state) phase transition at about 240 K and a second one at about 100 K. The magnetic measurements suggest the presence of magnetic clusters and a change in the nature of magnetic coupling between Co ions at low temperatures. A semiconducting type behavior and high negative magnetoresistance was found for the Ca-doped samples, while the Sr-doped ones were metallic and with negligible magnetoresistance. The results are analyzed in the frame of a phase separation scenario in the presence of the spin-state transitions of Co ions.
Journal of Applied Physics, 2002
The DyNi5−xAlx compounds crystallize in CaCu5-type structure for an aluminum content x⩽1.5 and in... more The DyNi5−xAlx compounds crystallize in CaCu5-type structure for an aluminum content x⩽1.5 and in HoNi2.6Ga2.4 type for x⩾2. The saturation moments per formula unit extrapolated at 0 K, in composition range x<2 are ∼9.2 μB in agreement with x-ray photoelectron spectroscopy studies which show negligible crystal field effects. For x⩾2 a mictomagnetic type contribution to magnetic ordering develops which becomes dominant only for the DyNi2Al3 compound. Band structure calculations on DyNi5−xAlx show that the Dy 5d band is polarized parallel to the 4f moment. For DyNi5 the nickel moments at 2c and 3g sites are antiparallel oriented to that of Dy. The nickel contributions to magnetization decrease when increasing aluminum content and are near nil for x⩾2. Above the Curie points the reciprocal susceptibilities follow linear dependencies. The effective nickel moments decrease from 2.11 μB/atom (x=0) to 0.87 μB/atom (x=2.5). The magnetic behavior of nickel is analyzed in models which take...
Journal of Alloys and Compounds, 2011
... c Emmanuel University, Oradea, Romania. Received 18 June 2010; revised 12 August 2010; accept... more ... c Emmanuel University, Oradea, Romania. Received 18 June 2010; revised 12 August 2010; accepted 25 August 2010. Available online 3 September 2010. Abstract. The Sr 2 FeMo 1−x M x O 6 double perovskites with M = W and Ta and x ≤ 0.3, were obtained by sintering at ...
International Journal of Modern Physics B, 2003
The Y ( M x Al 1 - x)3 compounds with M = Fe or Co crystallize in BaPb3-type structure for compos... more The Y ( M x Al 1 - x)3 compounds with M = Fe or Co crystallize in BaPb3-type structure for compositions x ≤ 0.4 while for x ≥ 0.6 the crystal structure is of PuNi3-type. Two phases were evidenced in the intermediate composition range. Magnetic measurements were performed on Y ( M x Al 1 - x)3 compounds in the temperature range 5–800 K and external field up to 10 T. The compounds with x ≥ 0.8 for M = Fe and Co are ferromagnetically ordered. For x < 0.8 a short range order and freezing effects of magnetic clusters originating from replacement of Fe by Al are evidenced. The mean magnetic moments of iron clusters as well as their number are estimated. For the samples with cobalt for x = 0.4 no magnetic order, down to 4.2 K was evidenced. For all compositions, the thermal variations of magnetic susceptibilities obey Curie–Weiss type dependencies.
Journal de Physique, 1983
2014 Nous présentons les résultats de mesures magnétiques et par effet Mössbauer effectuées sur d... more 2014 Nous présentons les résultats de mesures magnétiques et par effet Mössbauer effectuées sur des verres 20 Fe2O380[3 B2O3(1-x)PbOxAuOv] avec AuOv = K2O ou CaO. La modification de la fraction r des ions Fe2+ est proportionnelle à la différence entre la valence des ions A et celle du plomb ainsi qu'au contenu en AuOv. La variation avec la composition des valeurs de r est analysée en corrélation avec la composition des verres.
Solid State Communications, 1979
Electrical resistivity and thermoelectric power measurements on V205-MoO3 solid solutions with 1 ... more Electrical resistivity and thermoelectric power measurements on V205-MoO3 solid solutions with 1 ,2,5 and 10 mol.% MoO3 are reported. The experimental data are in agreement with the prediction of the model involving non-adiabatic small polarons.
physica status solidi (b), 1984
physica status solidi (a), 1997
Magnetic and ESR investigations on xEu2O3(1 - x) [3B2O3 . PbO] glasses in the temperature range 7... more Magnetic and ESR investigations on xEu2O3(1 - x) [3B2O3 . PbO] glasses in the temperature range 77 to 300 K are reported. The experimental data show a modified Curie-Weiss behavior. The paramagnetic Curie temperatures are negative indicating an antiferromagnetic order at lower temperatures. The Curie constants indicate the presence of europium ions in two valence states (2+ and 3+), in
Journal of Magnetism and Magnetic Materials, 2007
ABSTRACT We have studied the oxidation states of Fe and Mo and the presence of grain boundaries i... more ABSTRACT We have studied the oxidation states of Fe and Mo and the presence of grain boundaries in the magneto resistive (MR) compounds Sr2FeMoO6 by means of x-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy and electrical resistivity measurements. XPS of the Mo 3d and Fe 3s core levels is indicating a mixed valence state involving around 30% Fe 3+ -Mo 5+ and 70% Fe 2+ -Mo 6+ states. Mössbauer studies confirm the presence of a valence fluctuation state and an essential amount of grain boundaries in the present Sr2FeMoO6 crystals. Resistivities and magnetoresistance studies evidenced strong grain boundary effects.
International Journal of Modern Physics B, 2005
We present a detailed study of the polycrystalline perovskite manganites La 0.67 Ca 0.33 Al x Mn ... more We present a detailed study of the polycrystalline perovskite manganites La 0.67 Ca 0.33 Al x Mn 1-x O 3(x=0,0.1,0.15,0.5) at low temperatures and high magnetic fields, including electrical resistance, magnetization, ac susceptibility. The static magnetic susceptibility was also measured up to 1000 K. All the samples show colossal magnetoresistance behavior and the Curie temperatures decrease with Al doping. The data suggest the presence of correlated magnetic clusters near the ferromagnetic transition. This appears to be a consequence of the structural and magnetic disorder created by the random distribution of Al atoms.
Molecular Crystals and Liquid Crystals, 2004
Revue roumaine de physique, 1988
Emil Burzo, S Adam, G Adam Revue Roumaine de Physique 33:44, 457-61, 1988. ... in Nd sub 2 Fe sub... more Emil Burzo, S Adam, G Adam Revue Roumaine de Physique 33:44, 457-61, 1988. ... in Nd sub 2 Fe sub 1 sub 4 sub - sub x M sub x B (M=Co, Ni, Si, Mn, and Ru) and (Nd sub 1 sub - sub x R sub x ) sub 2 Fe sub 1 sub 4 B (R=Tb and Dy). ...
Landolt-Börnstein - Group III Condensed Matter, 2009
ABSTRACT
Journal of Optoelectronics and Advanced Materials
The time evolution of the physical properties of hard and soft magnetic materials is shortly revi... more The time evolution of the physical properties of hard and soft magnetic materials is shortly reviewed. Then, we analyse the magnetic properties of Nd5Fe67Cr8Nb2B18 nanocomposites, Nd-Fe-Co-Al-B hard magnetic phases and magnets as well as of Nd2Fe14-xMxC0.8B0.2 (M=Ni, Cu and Al) alloys. Some data on soft magnetic materials are also given. Finally, the magnetocaloric properties of ternary Gd-Co-B compounds are reported. Hard and soft magnetic materials, Magnetocaloric effect a) based on lecture given at MATEHN International Conference
Landolt-Börnstein - Group III Condensed Matter, 2005
This document is part of Subvolume I3 'Cyclosilicates' of Volume 27 'Magnetic prop... more This document is part of Subvolume I3 'Cyclosilicates' of Volume 27 'Magnetic properties of non-metallic inorganic compounds based on transition elements' of Landolt-Börnstein - Group III Condensed Matter. It contains the data on axinite-, ioaquinite-groups and related silicates (Figures).
Journal of Alloys and Compounds
The Sr2FeMo1-xMxO6 double perovskites with M = W and Ta and x <= 0.3, were obtained by sinteri... more The Sr2FeMo1-xMxO6 double perovskites with M = W and Ta and x <= 0.3, were obtained by sintering at 1300 degrees C. during 4 and 8 h, respectively. The perovskites crystallize in a tetragonal structure having 14/mmm space group. The grains are more homogeneous when sintering time is increased. The samples sintered longer time show higher values of saturation magnetizations, resistivities and magnetoresistivities than the samples sintered during 4 h. The intergrain tunnelling magnetoresistance as well as the intragrain contributions, respectively were analysed as function of temperature and external field. The changes in the physical properties, when the sintering time is increased, have been correlated with the number of antisite defects as well as the nature of grain boundaries. (C) 2010 Elsevier B.V. All rights reserved.
physica status solidi (c), 2004
ABSTRACT The GdxY1–xCo3NiB compounds form solid solutions in all the composition range having hex... more ABSTRACT The GdxY1–xCo3NiB compounds form solid solutions in all the composition range having hexagonal CeCo4B-type structure. The saturation magnetizations, at 4.2 K, decrease from 4.56 μB/f.u. (x = 1) up to a composition x = 0.275, when the resultant moment is nil and then increase up to 1.7 μB/fu for YCo3NiB.This behaviour is in agreement with a ferrimagnetic type ordering. The magnetic moments at various sites are analysed in correlation with their local environments. A magnetic moment is induced on Ni atoms. The mean effective cobalt and nickel moments seem to be little dependent on composition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic measurements and XPS studies were performed on LaNi5-xAlx, TbNi5-xAlx, DyNi5-xAlx, LaNi5... more Magnetic measurements and XPS studies were performed on LaNi5-xAlx, TbNi5-xAlx, DyNi5-xAlx, LaNi5-xCux and NdNi5-xCux systems. In addition, band structure calculations were also performed. The nickel moments in RNi5 (R=Nd, Tb, Dy) compounds are of ≅ 0.17 µ B and ≅ 0.25 µ B at 2c and 3g sites, respectively. The nickel moments, in low temperature range, decrease when increasing Al or Cu content and are practically nil for x > 1. The 4f-5d-3d exchange interactions were analyzed and the contributions of local 4f-5d and short range 5d-3d exchange interactions to 5d band polarization are estimated. An effective field of the order of (30-40) T is necessary to induce a nickel moment, at 1.7 K. Above the Curie temperatures, the effective nickel moments were determined. The LaNi5-xCux and LaNi5-xAlx systems, show, at T ≤ 10 K, a T2 dependence of the magnetic susceptibilities, while above a characteristic temperature T*, a Curie-Weiss contribution was evidenced. The magnetic behaviour of ni...
Journal of Magnetism and Magnetic Materials, 2010
The magnetic and electrical properties of polycrystalline Pr 1Àx A x CoO 3 cobaltites with A ¼ Ca... more The magnetic and electrical properties of polycrystalline Pr 1Àx A x CoO 3 cobaltites with A ¼ Ca, Sr and 0rxr0.5 were studied in the temperature range 4 KrTr1000 K and field up to 7 T. The X-ray analyses show the presence of only one phase having monoclinic or orthorhombic symmetry. The magnetic measurements indicate that the Ca-doped samples have at low temperatures, similar properties to the frustrated magnetic materials. PrCoO 3 is a paramagnetic insulator in the range from 4 to 1000 K. The Srdoped cobaltites exhibit two phase transitions: a paramagnetic-ferromagnetic (or magnetic phase separated state) phase transition at about 240 K and a second one at about 100 K. The magnetic measurements suggest the presence of magnetic clusters and a change in the nature of magnetic coupling between Co ions at low temperatures. A semiconducting type behavior and high negative magnetoresistance was found for the Ca-doped samples, while the Sr-doped ones were metallic and with negligible magnetoresistance. The results are analyzed in the frame of a phase separation scenario in the presence of the spin-state transitions of Co ions.
Journal of Applied Physics, 2002
The DyNi5−xAlx compounds crystallize in CaCu5-type structure for an aluminum content x⩽1.5 and in... more The DyNi5−xAlx compounds crystallize in CaCu5-type structure for an aluminum content x⩽1.5 and in HoNi2.6Ga2.4 type for x⩾2. The saturation moments per formula unit extrapolated at 0 K, in composition range x<2 are ∼9.2 μB in agreement with x-ray photoelectron spectroscopy studies which show negligible crystal field effects. For x⩾2 a mictomagnetic type contribution to magnetic ordering develops which becomes dominant only for the DyNi2Al3 compound. Band structure calculations on DyNi5−xAlx show that the Dy 5d band is polarized parallel to the 4f moment. For DyNi5 the nickel moments at 2c and 3g sites are antiparallel oriented to that of Dy. The nickel contributions to magnetization decrease when increasing aluminum content and are near nil for x⩾2. Above the Curie points the reciprocal susceptibilities follow linear dependencies. The effective nickel moments decrease from 2.11 μB/atom (x=0) to 0.87 μB/atom (x=2.5). The magnetic behavior of nickel is analyzed in models which take...
Journal of Alloys and Compounds, 2011
... c Emmanuel University, Oradea, Romania. Received 18 June 2010; revised 12 August 2010; accept... more ... c Emmanuel University, Oradea, Romania. Received 18 June 2010; revised 12 August 2010; accepted 25 August 2010. Available online 3 September 2010. Abstract. The Sr 2 FeMo 1−x M x O 6 double perovskites with M = W and Ta and x ≤ 0.3, were obtained by sintering at ...
International Journal of Modern Physics B, 2003
The Y ( M x Al 1 - x)3 compounds with M = Fe or Co crystallize in BaPb3-type structure for compos... more The Y ( M x Al 1 - x)3 compounds with M = Fe or Co crystallize in BaPb3-type structure for compositions x ≤ 0.4 while for x ≥ 0.6 the crystal structure is of PuNi3-type. Two phases were evidenced in the intermediate composition range. Magnetic measurements were performed on Y ( M x Al 1 - x)3 compounds in the temperature range 5–800 K and external field up to 10 T. The compounds with x ≥ 0.8 for M = Fe and Co are ferromagnetically ordered. For x < 0.8 a short range order and freezing effects of magnetic clusters originating from replacement of Fe by Al are evidenced. The mean magnetic moments of iron clusters as well as their number are estimated. For the samples with cobalt for x = 0.4 no magnetic order, down to 4.2 K was evidenced. For all compositions, the thermal variations of magnetic susceptibilities obey Curie–Weiss type dependencies.
Journal de Physique, 1983
2014 Nous présentons les résultats de mesures magnétiques et par effet Mössbauer effectuées sur d... more 2014 Nous présentons les résultats de mesures magnétiques et par effet Mössbauer effectuées sur des verres 20 Fe2O380[3 B2O3(1-x)PbOxAuOv] avec AuOv = K2O ou CaO. La modification de la fraction r des ions Fe2+ est proportionnelle à la différence entre la valence des ions A et celle du plomb ainsi qu'au contenu en AuOv. La variation avec la composition des valeurs de r est analysée en corrélation avec la composition des verres.
Solid State Communications, 1979
Electrical resistivity and thermoelectric power measurements on V205-MoO3 solid solutions with 1 ... more Electrical resistivity and thermoelectric power measurements on V205-MoO3 solid solutions with 1 ,2,5 and 10 mol.% MoO3 are reported. The experimental data are in agreement with the prediction of the model involving non-adiabatic small polarons.
physica status solidi (b), 1984
physica status solidi (a), 1997
Magnetic and ESR investigations on xEu2O3(1 - x) [3B2O3 . PbO] glasses in the temperature range 7... more Magnetic and ESR investigations on xEu2O3(1 - x) [3B2O3 . PbO] glasses in the temperature range 77 to 300 K are reported. The experimental data show a modified Curie-Weiss behavior. The paramagnetic Curie temperatures are negative indicating an antiferromagnetic order at lower temperatures. The Curie constants indicate the presence of europium ions in two valence states (2+ and 3+), in
Journal of Magnetism and Magnetic Materials, 2007
ABSTRACT We have studied the oxidation states of Fe and Mo and the presence of grain boundaries i... more ABSTRACT We have studied the oxidation states of Fe and Mo and the presence of grain boundaries in the magneto resistive (MR) compounds Sr2FeMoO6 by means of x-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy and electrical resistivity measurements. XPS of the Mo 3d and Fe 3s core levels is indicating a mixed valence state involving around 30% Fe 3+ -Mo 5+ and 70% Fe 2+ -Mo 6+ states. Mössbauer studies confirm the presence of a valence fluctuation state and an essential amount of grain boundaries in the present Sr2FeMoO6 crystals. Resistivities and magnetoresistance studies evidenced strong grain boundary effects.
International Journal of Modern Physics B, 2005
We present a detailed study of the polycrystalline perovskite manganites La 0.67 Ca 0.33 Al x Mn ... more We present a detailed study of the polycrystalline perovskite manganites La 0.67 Ca 0.33 Al x Mn 1-x O 3(x=0,0.1,0.15,0.5) at low temperatures and high magnetic fields, including electrical resistance, magnetization, ac susceptibility. The static magnetic susceptibility was also measured up to 1000 K. All the samples show colossal magnetoresistance behavior and the Curie temperatures decrease with Al doping. The data suggest the presence of correlated magnetic clusters near the ferromagnetic transition. This appears to be a consequence of the structural and magnetic disorder created by the random distribution of Al atoms.
Molecular Crystals and Liquid Crystals, 2004
Revue roumaine de physique, 1988
Emil Burzo, S Adam, G Adam Revue Roumaine de Physique 33:44, 457-61, 1988. ... in Nd sub 2 Fe sub... more Emil Burzo, S Adam, G Adam Revue Roumaine de Physique 33:44, 457-61, 1988. ... in Nd sub 2 Fe sub 1 sub 4 sub - sub x M sub x B (M=Co, Ni, Si, Mn, and Ru) and (Nd sub 1 sub - sub x R sub x ) sub 2 Fe sub 1 sub 4 B (R=Tb and Dy). ...
Landolt-Börnstein - Group III Condensed Matter, 2009
ABSTRACT
Journal of Optoelectronics and Advanced Materials
The time evolution of the physical properties of hard and soft magnetic materials is shortly revi... more The time evolution of the physical properties of hard and soft magnetic materials is shortly reviewed. Then, we analyse the magnetic properties of Nd5Fe67Cr8Nb2B18 nanocomposites, Nd-Fe-Co-Al-B hard magnetic phases and magnets as well as of Nd2Fe14-xMxC0.8B0.2 (M=Ni, Cu and Al) alloys. Some data on soft magnetic materials are also given. Finally, the magnetocaloric properties of ternary Gd-Co-B compounds are reported. Hard and soft magnetic materials, Magnetocaloric effect a) based on lecture given at MATEHN International Conference
Landolt-Börnstein - Group III Condensed Matter, 2005
This document is part of Subvolume I3 'Cyclosilicates' of Volume 27 'Magnetic prop... more This document is part of Subvolume I3 'Cyclosilicates' of Volume 27 'Magnetic properties of non-metallic inorganic compounds based on transition elements' of Landolt-Börnstein - Group III Condensed Matter. It contains the data on axinite-, ioaquinite-groups and related silicates (Figures).