Search results for: N.O. Moreno

Items from 1 to 20 out of 36 results

article

Structural and magnetic properties of LaCrO3 half-doped with Al

Romualdo S. Silva, Petrucio Barrozo, N.O. Moreno, J. Albino Aguiar

Ceramics International > 2016 > 42 > 13 > 14499- 14504

Structural and magnetic properties of LaCrO₃ half-doped with Al are reported in this work. Pure and half-doped samples were prepared by combustion synthesis using urea as fuel. The crystal structure was investigated by X-ray diffraction and Rietveld analysis. A structural phase transition caused by a decrease of the chemical pressure was observed. The scanning electron microscopy (SEM) images show...

article

Magnetocaloric and magnetic properties of SmFe0.5Mn0.5O3 complex perovskite

M.C. Silva-Santana, C.A. daSilva, P. Barrozo, E.J.R. Plaza, more

Journal of Magnetism and Magnetic Materials > 2016 > 401 > C > 612-617

In this paper, we have investigated the physical properties of SmFe_0.5Mn_0.5O₃ complex perovskite samples, synthesized by means of combustion reaction method. X-ray powder diffraction indicates the formation of single phase perovskite with orthorhombic structure. Low magnetic field measurements show remarkable transition at 234K related to spin reorientation. The magnetocaloric effect shows two peaks...

article

Preparation and crystallization of hollow α-Fe2O3 microspheres following the gas-bubble template method

L. de los Santos Valladares, L. León Félix, S.M. Espinoza Suarez, A.G. Bustamante Dominguez, more

Materials Chemistry and Physics > 2016 > 169 > C > 21-27

In this work we report the formation of hollow α-Fe₂O₃ (hematite) microspheres by the gas-bubble template method. This technique is simple and it does not require hard templates, surfactants, special conditions of atmosphere or complex steps. After reacting Fe(NO₃)₃.9H₂O and citric acid in water by sol–gel, the precursor was annealed in air at different temperatures between 180 and 600 °C. Annealing...

article

First principles study of the structural and electronic properties of double perovskite Ba2YTaO6 in cubic and tetragonal phases

C.E. Deluque Toro, Jairo Arbey Rodríguez M., D.A. Landínez Téllez, N.O. Moreno Salazar, more

Physica B: Condensed Matter > 2014 > 455 > C > 18-21

The Ba₂YTaO₆ double perovskite presents a transition from cubic (Fm−3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba₂YTaO₆ in space group Fm−3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density...

article

Magnetic properties of Fe–Al for quenched diluted spin-1 Ising model

A.S. Freitas, Douglas F. de Albuquerque, I.P. Fittipaldi, N.O. Moreno

Journal of Magnetism and Magnetic Materials > 2014 > 362 > Complete > 226-228

We study the phase diagram of Fe1−qAlq alloys via the quenched site diluted spin-1 ferromagnetic Ising model by employing effective field theory. One suggests a new approach to exchange interaction between nearest neighbors of Fe that depends on the powers of the Al (q) instead of the linear dependence proposed in other papers. In such model we propose the same kind of the exchange interaction in...

article

Fe–Mn alloys: A mixed-bond spin-1/2 Ising model version

A.S. Freitas, Douglas F. de Albuquerque, N.O. Moreno

Journal of Magnetism and Magnetic Materials > 2014 > 361 > Complete > 137-139

In this work, we apply the mixed-bond spin-1/2 Ising model to study the magnetic properties of Fe–Mn alloys in the α phase by employing the effective field theory (EFT). Here, we suggest a new approach to the ferromagnetic coupling between nearest neighbours Fe–Fe that depends on the ratio between the Mn–Mn coupling and the Fe–Mn coupling and of second power of the Mn concentration q in contrast to...

article

A new theoretical approach to the Fe1−qAlq in the bcc lattice by employing effective field theory

A.S. Freitas, D.F. de Albuquerque, N.O. Moreno

Physica A: Statistical Mechanics and its Applications > 2012 > 391 > 24 > 6332-6336

In this work, a study on a site diluted Ising model system is applied to the magnetic properties of the bcc disordered phase of FeAl alloys by employing effective field theory. Here, one suggests a new approach to exchange interaction between nearest neighbors of Fe that depends on the powers of the Al (q) instead of the linear dependence proposed in other papers. With this, we find an excellent agreement...

article

Structural and magnetic properties of pyrochlores Gd2−xMxRu2O7 (M=Ho, Y)

M.D.R. Marques, F.S. Portela, A.A.M. Oliveira, Petrucio Barrozo, more

Physica B: Physics of Condensed Matter > 2012 > 407 > 16 > 3106-3108

In this paper we investigated the structural and magnetic properties of the Gd _2−x M _x Ru ₂ O ₇ (M=Ho and Y, x=0.0, 0.1, 0.2, 1.0 and 2.0) pyrochlores. The samples were prepared by solid state reaction method, characterized structurally by X-ray diffraction with Rietveld refinement and magnetically by measuring the temperature dependence of the magnetization. X-ray...

article

An extended approach for computing the critical properties in the two-and three-dimensional lattices within the effective-field renormalization group method

Douglas F. de Albuquerque, Edimilson Santos-Silva, N.O. Moreno

Journal of Magnetism and Magnetic Materials > 2009 > 321 > 19 > L63-L64

In this letter we employing the effective-field renormalization group (EFRG) to study the Ising model with nearest neighbors to obtain the reduced critical temperature and exponents ν for bi- and three-dimensional lattices by increasing cluster scheme by extending recent works. The technique follows up the same strategy of the mean field renormalization group (MFRG) by introducing an alternative way...

article

Self-irradiation damage and 5f localization in PuCoGa5

C.H. Booth, M. Daniel, R.E. Wilson, E.D. Bauer, more

Journal of Alloys and Compounds > 2007 > 444-445 > Complete > 119-123

Understanding superconductivity in PuCoGa ₅ presents several challenges due to the presence of local moments and self-irradiation damage. We present X-ray absorption fine-structure measurements that further establish the presence of local 5f-electrons. Moreover, these data indicate even stronger localization after the PuCoGa ₅ sample has aged, indicating a possible mixed valent ground...

article

Monte Carlo studies of the cubic lattice mixed-bond Ising model

J.B. Santos-Filho, N.O. Moreno, D.F. de Albuquerque, A.S. de Arruda

Physica B: Physics of Condensed Matter > 2007 > 398 > 2 > 294-296

In this work, we used the Cluster Wolff algorithms to simulate the dynamics of the system. We obtained the thermodynamic quantities such as magnetization and susceptibility. Critical temperatures were estimated at the maximum of the susceptibility and with these values we made the phase diagram, TC versus p (the concentration of magnetic bonds) for different α values, being α the competition parameter...

article

Phase diagram and tricritical behavior of an Ising metamagnet model in a trimodal random field

A. Weizenmann, Maurício Godoy, A.S. de Arruda, Douglas F. de Albuquerque, more

Physica B: Physics of Condensed Matter > 2007 > 398 > 2 > 297-300

The phase diagram of an Ising metamagnet in a random magnetic field is studied by using mean-field equations from Bogoliubov's variational principle. The trimodal probability distribution is applied. The phase diagram in the t–h plane presents continuous and first-order transition lines. The phase transition lines, together with the critical points, were obtained for several random field values.

article

Spin glass state in Fe0.5Ni0.5TiO3 polycrystal

N.O. Moreno, J.D. Thompson, R.D. Taylor, J.L. Sarrao

Physica B: Physics of Condensed Matter > 2007 > 398 > 2 > 245-247

The spin glass Fe0.5Ni0.5TiO3 has been studied by DC/AC susceptibility as well as Mössbauer spectroscopy measurements. The data show a transition from a paramagnetic to an antiferromagnetic state at TN=116K and a reentrant spin-glass behavior is observed below TRSG=60K.

article

Magnetic excitations of the 2-D Sm spin layers in Sm(La,Sr)CuO4

F. Ronning, C. Capan, N.O. Moreno, J.D. Thompson, more

Journal of Magnetism and Magnetic Materials > 2007 > 310 > 2 Part 2 > e392-e393

We present specific heat and susceptibility data on Sm(La,Sr)CuO4 in magnetic fields up to 9T and temperatures down to 100mK. We find a broad peak in specific heat which is insensitive to magnetic field at a temperature of 1.5K with a value of 2.65J/molK. The magnetic susceptibility at 5T continues to increase down to 2K, the lowest temperature measured. The data suggest that the Sm spin system may...

article

Electron spin resonance (ESR) in multiferroic TbMnO3

N.O. Moreno, J.G.S. Duque, P.G. Pagliuso, C. Rettori, more

Journal of Magnetism and Magnetic Materials > 2007 > 310 > 2 Part 2 > e364-e366

We report temperature dependent X-Band (ν∼9.4GHz) electron spin resonance (ESR) measurement in a single crystal of TbMnO3. A single Lorentzian ESR line with an isotropic g∼ 1.96 was observed for T⩾120K up to 600K. The ESR signal is attributed to the Mn3+ ions in a insulator environment. For the three crystallographic axes the temperature dependence ESR linewidth shows a strong broadening as the temperature...

article

Critical behavior in a random field classical XY model for amorphous systems

D.F. de Albuquerque, S.R.L. Alves, A.S. de Arruda, N.O. Moreno

Physica B: Physics of Condensed Matter > 2006 > 384 > 1-2 > 212-214

By using the differential operator technique and the effective field theory (EFT) scheme, the critical behavior of amorphous classical XY ferromagnet in a random field is studied. The phase diagram in the T–H and T–α planes on a simple cubic lattice for a cluster with two spins is obtained. Calculation is carried out within the EFT approximation. Tricritical points, reentrant phenomena and influence...

article

On the random field Ising model in a honeycomb lattice

Douglas F. de Albuquerque, I.P. Fittipaldi, J.R. de Sousa, N.O. Moreno

Physica B: Physics of Condensed Matter > 2006 > 384 > 1-2 > 230-232

Within the framework of the effective field theory we discuss the effects of an applied field H, on magnetic properties of the random field Ising model in a honeycomb lattice. The phase diagram in the T–H plane for clusters with one spin is obtained in a finite size cluster scheme. On the other hand, we observe that for h⩾1, the contribution of the random magnetic field is more accentuated in the...

chapter

Studies of Electron Spin Resonance (ESR) in TbMnO3 multiferroic compound

J.S. Duque, P.G. Pagliuso, C. Rettori, N.O. Moreno, more

INTERMAG 2006 - IEEE International Magnetics Conference > 244

INTERMAG 2006 - IEEE International Magnetics Conference

We report temperature dependent X-Band (v ~ 9.5 GHz) Electron Spin Resonance (ESR) measurements in a single crystal of TbMnO₃. The temperature dependence of this ESR linewidth was investigated in the three crystallographic orientations. The field-dependence of ESR line investigated by ESR experiments using other Band frequencies will be also discussed. TbMnO₃ is orthorhombic insulator of the multiferroic...

article

Anisotropic intermediate valence in Yb2Rh3Ga9

A.D. Christianson, J.M. Lawrence, A.M. Lobos, A.A. Aligia, more

Physica B: Physics of Condensed Matter > 2006 > 378-380 > Complete > 752-753

We report measurements of the inelastic neutron scattering spectrum for the anisotropic intermediate valence system Yb ₂ Rh ₃ Ga ₉ . Calculations for the Anderson impurity model with crystal field terms within an approach based on the non-crossing approximation have been performed for the inelastic neutron scattering spectrum as well as other thermodynamic quantities. These...

article

Pressure–temperature–composition phase diagram of Ce2MIn8 (M=Rh,Ir)

E.N. Hering, H.A. Borges, S.M. Ramos, M.B. Fontes, more

Physica B: Physics of Condensed Matter > 2006 > 378-380 > Complete > 423-425

In this work a preliminary pressure–temperature–composition phase diagram for the Ce2Rh(1-x)IrxIn8 heavy-fermions (HF) materials is reported, built from pressure-dependent electrical resistivity (ρ(T)) measurements on single-crystalline samples. Although neither of the two end members is an ambient-pressure SC, a transition to a zero-resistance (ZR) state was found at ambient pressure (TC≈600mK) in...

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Search results for: N.O. Moreno

Structural and magnetic properties of LaCrO3 half-doped with Al

Magnetocaloric and magnetic properties of SmFe0.5Mn0.5O3 complex perovskite

Preparation and crystallization of hollow α-Fe2O3 microspheres following the gas-bubble template method

First principles study of the structural and electronic properties of double perovskite Ba2YTaO6 in cubic and tetragonal phases

Magnetic properties of Fe–Al for quenched diluted spin-1 Ising model

Fe–Mn alloys: A mixed-bond spin-1/2 Ising model version

A new theoretical approach to the Fe1−qAlq in the bcc lattice by employing effective field theory

Structural and magnetic properties of pyrochlores Gd2−xMxRu2O7 (M=Ho, Y)

An extended approach for computing the critical properties in the two-and three-dimensional lattices within the effective-field renormalization group method

Self-irradiation damage and 5f localization in PuCoGa5

Monte Carlo studies of the cubic lattice mixed-bond Ising model

Phase diagram and tricritical behavior of an Ising metamagnet model in a trimodal random field

Spin glass state in Fe0.5Ni0.5TiO3 polycrystal

Magnetic excitations of the 2-D Sm spin layers in Sm(La,Sr)CuO4

Electron spin resonance (ESR) in multiferroic TbMnO3

Critical behavior in a random field classical XY model for amorphous systems

On the random field Ising model in a honeycomb lattice

Studies of Electron Spin Resonance (ESR) in TbMnO3 multiferroic compound

Anisotropic intermediate valence in Yb2Rh3Ga9

Pressure–temperature–composition phase diagram of Ce2MIn8 (M=Rh,Ir)

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