viorel pop | Babes-Bolyai University (original) (raw)
Papers by viorel pop
A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system h... more A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system has been performed. The ThCo4B compound crystallizes in a hexagonal structure, space group P6/mmm with a = 5.008 Å and c = 7.003 Å. The ThCo4B system orders ferromagnetically under a Curie temperature of 303 K. The influence of the local environment on the magnitude of Co
AIP Conference Proceedings, 2007
A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system h... more A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system has been performed. The ThCo4B compound crystallizes in a hexagonal structure, space group P6/mmm with a = 5.008 Å and c = 7.003 Å. The ThCo4B system orders ferromagnetically under a Curie temperature of 303 K. The influence of the local environment on the magnitude of Co
Solid State Communications, 2014
The electronic properties of RCo 5 À x M x (R ¼Er, Sm, Tm; M ¼Si, Ga, Al; x ¼ 0 and 1) compounds ... more The electronic properties of RCo 5 À x M x (R ¼Er, Sm, Tm; M ¼Si, Ga, Al; x ¼ 0 and 1) compounds were investigated by X-ray photoelectron spectroscopy (XPS). The study was focused on the Co 3s exchange splitting, the valence bands and chemical shifts of the elements from the analyzed compounds. The Co 2p 3/2 core-level chemical shifts were described by means of the Auger parameters and Wagner plot. The hybridization between the R 5d6s and M 3sp and 4sp states and Co 3d states leads to a partial filling of the Co 3d band and to a decrease of the Co magnetic moments in comparison with the value in pure Co metal, in good agreement with the magnetic measurements.
Journal of Optoelectronics and Advanced Materials
ABSTRACT
Revista de pediatrie, obstetrică şi ginecologie. Pediatria
Materials Science Forum
The GdCo,_,Ni,B alloys, for x d 3 and GdCo,_,Fe,B alloys for x 61.5 crystallize in a hexagonal st... more The GdCo,_,Ni,B alloys, for x d 3 and GdCo,_,Fe,B alloys for x 61.5 crystallize in a hexagonal structure of CeCo,B-type. The magnetic measurements performed in the temperature range 4.2-900 K show that GdCo,_,M,B compounds (M = Fe or Ni) are ferrimagnetically ordered. The mean cobalt moments increase when cobalt is substituted by iron and decrease when it is replaced by nickel. Above the Curie temperatures, the reciprocal susceptibilities for GdCo,_,Ni,B alloys show a nonlinear temperature dependence. The exchange fields acting on cobalt atoms were evaluated. The variations of the cobalt moments are proportional to those of the exchange fields.
Revista de pediatrie, obstetrică şi ginecologie. Pediatria
Polycrystalline solids with grain size less than 100 nm are called nanocrystalline materials. Nan... more Polycrystalline solids with grain size less than 100 nm are called nanocrystalline materials. Nanocrystalline structures offer a new opportunity to improve current magnetic materials. This refers to materials such as permanent magnets, soft magnetic materials, recording media and also to materials involved in spin electronics. The properties of nanocrystalline m aterials are very often superior to those of conventional polycrystalline coarse grain materials. These materials can be produced using various methods and different starting phases: vapour (inert gas condensation, sputtering, plasma processing, vapour deposition), liquid (electrodeposition, rapid solidification) or solid (mechanical alloying, severe plastic deformation, spark erosion) . A survey on mechanical alloying and rapid quenching as a method to obtain nanostructured permanent magnets and soft magnetic materials will be given. The influence of the annealing on the structure and microstructure will be also discussed. A short description concerning the synthesis of monodisperse ironplatinum nanoparticles by chemical methods will be also presented. This study does not refer to magnetic nanostructures such as dots and arrays, nanowires, multilayers or nanojonctions. Ecole Franco-Roumaine : Magnétisme des systèmes nanoscopiques et structures hybrides -Brasov, 2003 Nanostructured magnetic metastable alloys Viorel Pop VI.1 -2 nanostructured materials: crystallites diameter, D, and volume fraction of nanocrystalline phases, V cr . In hard magnetic nanocrystalline materials full or almost full crystallization is required. The critical dimension for the soft phase, below which the soft phase is rigidly coupled to the hard phase, is found to be roughly twice the width of domain wall in the hard phase, d h [20]:
physica status solidi (a)
ABSTRACT
Les poudres nanocristallines Ni79Fe16Mo5 (Supermalloy) et Ni77Fe14Cu5Mo4 ont été obtenues par bro... more Les poudres nanocristallines Ni79Fe16Mo5 (Supermalloy) et Ni77Fe14Cu5Mo4 ont été obtenues par broyage mécanique de haute énergie sous atmosphère d'argon et par combinaison de broyage mécanique et recuit. Les temps de broyage testés ont été compris entre 1 et 28 heures. Pour l'élimination des tensions internes résiduelles, des traitements thermiques ont été effectués à 350 °C. La taille des cristallites a été estimée à 11 ± 2 nm pour le Supermalloy après 16 h de broyage et à 18 ± 2 nm pour NiFeCuMo après 24 h de broyage suivi par 4 h de recuit à 350 °C. L'évolution de la formation des nouvelles phases par mécanosynthèse a été étudiée par diffraction des rayons X et mesures magnétiques. L'homogénéité chimique et la morphologie des particules de poudre ont été mises en évidence par microanalyse des rayons X (EDX) et par microscopie électronique à balayage (MEB).
Revista de chirurgie, oncologie, radiologie, o. r. l., oftalmologie, stomatologie. Oftalmologie
The crystal structure and magnetic properties in the paramagnetic range of RCo 4 Si (R = Gd, Tb, ... more The crystal structure and magnetic properties in the paramagnetic range of RCo 4 Si (R = Gd, Tb, Dy, Ho, Er) intermetallic compounds have been investigated. The compounds crystallise in a hexagonal crystal structure of CaCu 5 type, space group P6/mmm. The Curie temperatures range from 336 K (R = Er) to 431 K (R = Gd). The effective cobalt moments were computed assuming an effective rare earth moment as in R 3+ free ions.
Solid State Communications
ABSTRACT
Journal of Applied Physics
ABSTRACT
IEEE Transactions on Magnetics
ABSTRACT
IEEE Transactions on Magnetics
Journal of Magnetism and Magnetic Materials
Magnetic measurements were performed on YBa2(Cu I xMx)307 ,s system with M = Cr, Ni, Zn and A1 in... more Magnetic measurements were performed on YBa2(Cu I xMx)307 ,s system with M = Cr, Ni, Zn and A1 in the temperature range 4-400 K and fields up to 70 kOe. The hysteresis loops as well as the magnetic behaviour above the superconducting transition temperatures are discussed in correlation with superconducting properties.
IEEE Transactions on Magnetics
lbstract-The results of magnetic measurements performed on YRaz ( CUI -x%nx)J 0 7 -3 supercoridii... more lbstract-The results of magnetic measurements performed on YRaz ( CUI -x%nx)J 0 7 -3 supercoridiicting materials with x i (1.1, in the temperature range 5-300 K and flelds up tu 70 kOe are reported. The rate of induction of Cui' ions, as compared to the number of Zn ones, is Irl for XI UJJFi. For higher zinr cnritent the number of Cui+ ions i~ fimaller than that of Zn'+ ions. The rec.iprooe1 of rribical t.nrnperature T;' and of critiral current denwitius, j;' , are linearly deponctent on (;U'+ content.
IEEE Transactions on Magnetics
Magnetic properties of (GdxYl.x)n+lCo3n+sBzn compounds with n = 1, 2, 3 and n ->were studied in t... more Magnetic properties of (GdxYl.x)n+lCo3n+sBzn compounds with n = 1, 2, 3 and n ->were studied in the temperature range 4-800 K and external field up to 7 T. The compounds with x20.2 are ferrimagnetically ordered. The cobalt and gadolinium magnetizations at 4 K, compensate at x=0.43 (n=l), x=0.31 (n=2) and x=0.26 (n=3). Within a given series, the mean cobalt moments determined at 4K are strongly dependent on the composition, while the effective cobalt moments deduced from the Curie constants in the paramagnetic phase are only a little composition dependent. The magnetic behaviour of cobalt in the studied system is analyzed.
A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system h... more A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system has been performed. The ThCo4B compound crystallizes in a hexagonal structure, space group P6/mmm with a = 5.008 Å and c = 7.003 Å. The ThCo4B system orders ferromagnetically under a Curie temperature of 303 K. The influence of the local environment on the magnitude of Co
AIP Conference Proceedings, 2007
A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system h... more A detailed theoretical investigation of the electronic and magnetic properties of ThCo4B system has been performed. The ThCo4B compound crystallizes in a hexagonal structure, space group P6/mmm with a = 5.008 Å and c = 7.003 Å. The ThCo4B system orders ferromagnetically under a Curie temperature of 303 K. The influence of the local environment on the magnitude of Co
Solid State Communications, 2014
The electronic properties of RCo 5 À x M x (R ¼Er, Sm, Tm; M ¼Si, Ga, Al; x ¼ 0 and 1) compounds ... more The electronic properties of RCo 5 À x M x (R ¼Er, Sm, Tm; M ¼Si, Ga, Al; x ¼ 0 and 1) compounds were investigated by X-ray photoelectron spectroscopy (XPS). The study was focused on the Co 3s exchange splitting, the valence bands and chemical shifts of the elements from the analyzed compounds. The Co 2p 3/2 core-level chemical shifts were described by means of the Auger parameters and Wagner plot. The hybridization between the R 5d6s and M 3sp and 4sp states and Co 3d states leads to a partial filling of the Co 3d band and to a decrease of the Co magnetic moments in comparison with the value in pure Co metal, in good agreement with the magnetic measurements.
Journal of Optoelectronics and Advanced Materials
ABSTRACT
Revista de pediatrie, obstetrică şi ginecologie. Pediatria
Materials Science Forum
The GdCo,_,Ni,B alloys, for x d 3 and GdCo,_,Fe,B alloys for x 61.5 crystallize in a hexagonal st... more The GdCo,_,Ni,B alloys, for x d 3 and GdCo,_,Fe,B alloys for x 61.5 crystallize in a hexagonal structure of CeCo,B-type. The magnetic measurements performed in the temperature range 4.2-900 K show that GdCo,_,M,B compounds (M = Fe or Ni) are ferrimagnetically ordered. The mean cobalt moments increase when cobalt is substituted by iron and decrease when it is replaced by nickel. Above the Curie temperatures, the reciprocal susceptibilities for GdCo,_,Ni,B alloys show a nonlinear temperature dependence. The exchange fields acting on cobalt atoms were evaluated. The variations of the cobalt moments are proportional to those of the exchange fields.
Revista de pediatrie, obstetrică şi ginecologie. Pediatria
Polycrystalline solids with grain size less than 100 nm are called nanocrystalline materials. Nan... more Polycrystalline solids with grain size less than 100 nm are called nanocrystalline materials. Nanocrystalline structures offer a new opportunity to improve current magnetic materials. This refers to materials such as permanent magnets, soft magnetic materials, recording media and also to materials involved in spin electronics. The properties of nanocrystalline m aterials are very often superior to those of conventional polycrystalline coarse grain materials. These materials can be produced using various methods and different starting phases: vapour (inert gas condensation, sputtering, plasma processing, vapour deposition), liquid (electrodeposition, rapid solidification) or solid (mechanical alloying, severe plastic deformation, spark erosion) . A survey on mechanical alloying and rapid quenching as a method to obtain nanostructured permanent magnets and soft magnetic materials will be given. The influence of the annealing on the structure and microstructure will be also discussed. A short description concerning the synthesis of monodisperse ironplatinum nanoparticles by chemical methods will be also presented. This study does not refer to magnetic nanostructures such as dots and arrays, nanowires, multilayers or nanojonctions. Ecole Franco-Roumaine : Magnétisme des systèmes nanoscopiques et structures hybrides -Brasov, 2003 Nanostructured magnetic metastable alloys Viorel Pop VI.1 -2 nanostructured materials: crystallites diameter, D, and volume fraction of nanocrystalline phases, V cr . In hard magnetic nanocrystalline materials full or almost full crystallization is required. The critical dimension for the soft phase, below which the soft phase is rigidly coupled to the hard phase, is found to be roughly twice the width of domain wall in the hard phase, d h [20]:
physica status solidi (a)
ABSTRACT
Les poudres nanocristallines Ni79Fe16Mo5 (Supermalloy) et Ni77Fe14Cu5Mo4 ont été obtenues par bro... more Les poudres nanocristallines Ni79Fe16Mo5 (Supermalloy) et Ni77Fe14Cu5Mo4 ont été obtenues par broyage mécanique de haute énergie sous atmosphère d'argon et par combinaison de broyage mécanique et recuit. Les temps de broyage testés ont été compris entre 1 et 28 heures. Pour l'élimination des tensions internes résiduelles, des traitements thermiques ont été effectués à 350 °C. La taille des cristallites a été estimée à 11 ± 2 nm pour le Supermalloy après 16 h de broyage et à 18 ± 2 nm pour NiFeCuMo après 24 h de broyage suivi par 4 h de recuit à 350 °C. L'évolution de la formation des nouvelles phases par mécanosynthèse a été étudiée par diffraction des rayons X et mesures magnétiques. L'homogénéité chimique et la morphologie des particules de poudre ont été mises en évidence par microanalyse des rayons X (EDX) et par microscopie électronique à balayage (MEB).
Revista de chirurgie, oncologie, radiologie, o. r. l., oftalmologie, stomatologie. Oftalmologie
The crystal structure and magnetic properties in the paramagnetic range of RCo 4 Si (R = Gd, Tb, ... more The crystal structure and magnetic properties in the paramagnetic range of RCo 4 Si (R = Gd, Tb, Dy, Ho, Er) intermetallic compounds have been investigated. The compounds crystallise in a hexagonal crystal structure of CaCu 5 type, space group P6/mmm. The Curie temperatures range from 336 K (R = Er) to 431 K (R = Gd). The effective cobalt moments were computed assuming an effective rare earth moment as in R 3+ free ions.
Solid State Communications
ABSTRACT
Journal of Applied Physics
ABSTRACT
IEEE Transactions on Magnetics
ABSTRACT
IEEE Transactions on Magnetics
Journal of Magnetism and Magnetic Materials
Magnetic measurements were performed on YBa2(Cu I xMx)307 ,s system with M = Cr, Ni, Zn and A1 in... more Magnetic measurements were performed on YBa2(Cu I xMx)307 ,s system with M = Cr, Ni, Zn and A1 in the temperature range 4-400 K and fields up to 70 kOe. The hysteresis loops as well as the magnetic behaviour above the superconducting transition temperatures are discussed in correlation with superconducting properties.
IEEE Transactions on Magnetics
lbstract-The results of magnetic measurements performed on YRaz ( CUI -x%nx)J 0 7 -3 supercoridii... more lbstract-The results of magnetic measurements performed on YRaz ( CUI -x%nx)J 0 7 -3 supercoridiicting materials with x i (1.1, in the temperature range 5-300 K and flelds up tu 70 kOe are reported. The rate of induction of Cui' ions, as compared to the number of Zn ones, is Irl for XI UJJFi. For higher zinr cnritent the number of Cui+ ions i~ fimaller than that of Zn'+ ions. The rec.iprooe1 of rribical t.nrnperature T;' and of critiral current denwitius, j;' , are linearly deponctent on (;U'+ content.
IEEE Transactions on Magnetics
Magnetic properties of (GdxYl.x)n+lCo3n+sBzn compounds with n = 1, 2, 3 and n ->were studied in t... more Magnetic properties of (GdxYl.x)n+lCo3n+sBzn compounds with n = 1, 2, 3 and n ->were studied in the temperature range 4-800 K and external field up to 7 T. The compounds with x20.2 are ferrimagnetically ordered. The cobalt and gadolinium magnetizations at 4 K, compensate at x=0.43 (n=l), x=0.31 (n=2) and x=0.26 (n=3). Within a given series, the mean cobalt moments determined at 4K are strongly dependent on the composition, while the effective cobalt moments deduced from the Curie constants in the paramagnetic phase are only a little composition dependent. The magnetic behaviour of cobalt in the studied system is analyzed.