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Structural and electronic properties of the Sr2MnSbO6 perovskite in cubic (Fm-3m) and tetragonal (I4m and P/4mnc) crystallographic phases have been determined using the Full Potential Linearized. Augmented Plane Waves (FP-LAPW) method, in the framework of the Density Functional Theory (DFT). The exchange and correlation effects were treated using the Generalized Gradient. Approximation plus the Hubbard term (GGA+U) approach, in order to describe the strong on-site Coulomb repulsion among the localized d-Mn electrons. The structural stability was determined by fitting of the total energy values to the Murnaghan equation of state. The values for the structural parameters are in good agreement with experimental results reported in the literature. The study of the electronic properties carried out through the graphical presentation of the densities of states for the two spin polarizations shows that the compound presents half-metallic behavior.

We report here the synthesis process of the perovskite-like complex material Bi0.5R0.5FeO3 (R=Eu, Sm, Dy) using the ceramic method, as well as its structural, optical, magnetic, and electrical characterizations. Refined X-ray diffraction data revealed that this material crystallizes in an orthorhombic structure (space group Pnma number 62). The band gap value in the optical response shown in the diffuse reflectance spectroscopy curve was typical of semiconductor materials. The magnetization exhibited a very low coercive field hysteretic behavior, which is characteristic of weak ferromagnetism, for all temperatures examined below 300 K and the various magnetic fields applied. The real and complex electric permittivity curves showed the occurrence of dielectric relaxation processes at 113 K in agreement with reports of pyroelectric and thermo-stimulated currents as a function of temperature revealing the appearance of ferroelectric polarization below 113 K with possible magnetoelectric coupling. On the other hand, we made a theoretical study of the electronic structure with and without the inclusion of a Berry distortional phase and ab-initio calculations following the density functional theory formalism and the pseudopotential plane wave method. In this formalism, the exchange and correlation mechanisms are described by the generalized gradient approach (GGA + U) considering spin polarization. The Berry phase analysis suggested the occurrence of ferroelectricity at temperatures below 113 K consistent with the experimental analysis evidencing a biferroic behavior at low temperatures given that the distortional phase introduces hybridizations between the 3d-Fe and 2p-O states favoring the appearance of Dzyaloshinskii-Moriya interactions, which, in turn, facilitate the appearance of ferroelectricity coexisting with a weak ferromagnetism. The thermodynamic properties in the presence or absence of the Berry phase by means of the Debye quasiharmonic model revealed the appearance of a ferroelectric transition at 113 K, which corroborates their magnetoelectric nature at low temperatures. The ferromagnetic semiconducting character found at room temperature enhances this material for applications in spintronics technology.

Physical properties of clay minerals are essential in the evaluation for applications and new potential uses of geological materials. This study presents results of optical, electrical, structural, compositional and morphological analysis of Hillite (0.967) / Chlorite (0.013) / Hematite (0.02) clay mineral extracted from the Machado mountain region in the municipality of Tarairá, department of Vaupés, Colombia. The extracted clay was subjected to treatments to separate it from the others geological compounds before the characterization process. The observed platy morphology allowed to perform a size grain analysis which confirmed the clay-extraction. Particles with 0.8- 1.4 mm diameter and two pseudo-modes distribution in the area histogram were found. The bimodal distribution is assumed to be caused due to the differences between periodic ages of formation of the minerals in the extraction region. Structurally, we found a monoclinic structure with residues of triclinic polymorphous and Hexagonal scalenohedral segregated structures. The XRD analysis was based in the EDS measurements, given the stoichiometry of the sample. Also, a big absorption in the optical UV-range with an effective band gap in the clay to 2.852(8) eV was found. The electrical properties of the clay showed a strong non-linear insulator behavior. Electrical losses by polarizing the sample were decreased by a previous heating. Finally, the complete physical properties analysis allowed to introduce this material as an inexpensive, time efficient insulator.

Synthesis of the SmBa2Cu3O7–δ superconducting material by the standard solid-state reaction is reported. DC resistivity measurements were performed to analyse the conductivity excess close to the superconducting transition. The fluctuation analysis was performed by the method of logarithmic temperature derivative of the paraconductivity. A bulk Tc = 93.004 K was determined through the extrapolation of the genuinely critical regime, which is explained from the dynamical scaling theory. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov–Larkin theory. From the analysis, the occurrence of Gaussian-like fluctuations associated to dimensional d = 3 and d = 2 pairing regimes and fluctuation developing in fractal topologies with d = 2.6 and d = 1.3 are established. The coherence length, the Ginzburg number, the jump in the specific heat δc at T = Tc, the penetration depth λ(0), the critical magnetic fields Bc1(T) and Bc2(T) and the critical current density Jc(0) were theoretically determined for this superconducting material. Results largely agree with experimental reports for RBa2Cu3O7–δ (R = Rare Earth elements) and YBa2Cu3O7–δ superconductors.

In this work the synthesis by thermal evaporation and optical characterization of the semiconductor thin film lead bromide (PbBr2) is reported, discussing its possible applicability in attenuation of UV radiation and ionizing radiation. In order to show the quality of the samples and their possible application, a series of experimental studies was carried out by means of X-ray diffraction that allowed establishing the crystallinity of the samples and scanning electron microscopy for the study of surface morphology, evidencing a high degree of film coating. Diffuse reflectance and transmittance spectroscopy experiments were used to study the optical properties of the material, finding a weakly semiconductor optical gap of 3.5 eV, which absorbs much of the radiation from a broad spectrum of ultraviolet, from 200 to 350 nm. The high value of the Pb atomic number favors the absorption of high-energy photons, and the mass absorption coefficient as well as the appearance of a doublet of transitions in the PL spectrum in the UV radiation regime, suggest the applicability of PbBr2 in the design of medical diagnostic and treatment equipment that involves ionizing radiation. Additionally, high transparency of the thin film was found as corroborated by the extinction coefficient, which could be useful for applications in microelectronic devices.

Ceramic samples of Tb2FeCoO6 were synthesized by the solid-state reaction recipe. The crystallographic analysis revealed that the material crystallizes into a complex perovskite-type orthorhombic structure (space group P21/n, # 14) with octahedral distortions. The surface topography of the material was evaluated by means of scanning electron microscopy, observing densified submicrometric granular characteristics in the form of polyform sheets. Energy scattering spectra showed 98% agreement between the experimental composition and the stoichiometry of the Tb2FeCoO6 formula. The DC magnetization curves as a function of temperature exhibit irreversible behavior at low temperatures related to the distortionary character of the Fe–O6 and Co–O6 octahedra in the structure. Magnetization hysteresis curves as a function of the applied field at temperatures from 5 K up to 300 K reveal a ferromagnetic type ordering in the material. The I–V characteristic suggests a semiconductor electrical response with a varistor-type tendency and strong dependence of the polycrystalline nature of the samples. Calculations of band structure and density of electronic states predict the semiconductor characteristic for this double perovskite, with Eg = 2.48 eV and the ferromagnetic behavior is attributed to extended super-exchange spin interaction in the Fe–O–Co ions. The ferromagnetic semiconductor nature of the Tb2FeCoO6 material foresees potential applications in the novel spintronics industry.

To produce functional active layers for photodetector devices, thin films of organic–inorganic CH3NH3PbI3 perovskite semiconductor have been grown by a close-space sublimation procedure and a hybrid dipping technique. x-Ray diffraction analysis was used to evaluate the crystalline quality of the thin films, confirming the achievement of a tetragonal structure of perovskite type in space group I4/mcm. Morphological analysis by scanning electron microscopy revealed a homogeneous and compact granular surface distribution. Kubelka–Munk analysis of the optical response measured by ultraviolet–visible (UV–Vis) spectrophotometry yielded an energy bandgap of 1.57 eV for the thin films produced by the close-space sublimation technique and 1.59 eV for those obtained by dipping. Photoluminescence experiments corroborated these bandgap values. The I–V characteristics of both thin films obtained at different incident laser powers and a wavelength of 650 nm demonstrated their potential for use as active layers in photodetector devices.

En la última década los nanomateriales magnéticos se han utilizado ampliamente en el campo de la química, la física, la ingeniería y la medicina debido a sus propiedades ópticas, magnéticas y de conducción, y como agentes de contraste en resonancia magnética. Se ha evaluado su influencia en el tratamiento de tumores cancerosos y está despertando gran interés en sistemas de reparación ambiental como absorbentes magnéticos que atrapan partículas de metal y algunos contaminantes. En este estudio se analizó la influencia de los parámetros de proceso en la obtención de nanopartículas magnéticas bajo tres métodos de síntesis química. La caracterización morfológica se hizo por microscopía electrónica de barrido (SEM), su composición elemental se estudió mediante espectroscopia de energía dispersiva de rayos x (EDS), y su estructura, mediante difracción de rayos x (XRD). Los resultados evidenciaron una gran influencia del método de obtención, como se reflejó en la variabilidad del tamaño de las nanopartículas. Es de resaltar la obtención de partículas a escala nanométrica, con predominancia de estructuras Fe3O4 (magnetita) y Fe2O3 (maghemita), lo cual supondría propiedades de superparamagnetismo que abrirían el camino a un amplio abanico de aplicaciones futuras con su producción a bajo costo y de fácil acceso. In the last decade, magnetic nanomaterials have been widely used in the fields of chemistry, physics, engineering, and medicine due to their optical, magnetic, and conductive properties, and as contrast agents in magnetic resonance. Their influence in the treatment of cancerous tumors has been evaluated and has sparked great interest in its use in environmental repair systems such as magnetic absorbers that trap metal particles and some contaminants. Here we analyze the influence of process parameters to obtain magnetic nanoparticles under three chemical synthesis methods. Its morphological characterization was performed by scanning electron microscopy (SEM), its elemental composition by energy dispersive spectroscopy (EDS), and its structure by x-ray diffraction (XRD). Our results showed that the obtention method had a great influence as evidenced by the variability in nanoparticle sizes. It is worth highlighting that we obtained particles at a nanometric scale, especially Fe3O4 (magnetite) and Fe2O3 (maghemite) structures, with potential superparamagnetism properties that could open a wide range of future applications for the production of these materials at low cost and easy access.

In search of unconventional ferromagnetic mechanisms in perovskite-like materials, the synthesis process, crystal structure, surface morphology, composition, and optical and magnetic behaviors of the narrowly studied rare-earth antimoniate Ba2SbSmO6, as well as its electronic structure calculated using the density functional theory, are reported in the present. Samples were synthesized by means of the solid-state reaction method. The structural analysis of the obtained compound was performed by Rietveld refinement of the experimental X-ray diffraction experimental data, which revealed its crystallization in a cubic complex perovskite, belonging to the space group Fm $$\stackrel{-}{3}$$ m (#225) with lattice parameter a = 8.5085(5) A. Surface morphological studies revealed the polycrystalline character of the material, with inhomogeneous granular microstructure and nanometric average size. The measured composition is close to that expected from the stoichiometry of the material. Temperature-dependent magnetic susceptibility measurements exhibited magnetic anisotropy effects and magnetization hysteresis curves showed weak ferromagnetic response for the examined temperature values. The electronic structure was calculated by means linearized augmented plane waves (FP-LAPW) in the framework of the density functional theory (DFT). Curves of density of states as a function of the wave number revealed the insulator behavior of the Ba2SbSmO6 material. The weak ferromagnetism exhibited by this perovskite-like compound is attributed to the occurrence of spin-orbit interaction effects of the 4f-Sm3+ electrons hybridized with 2p–O2− orbitals.

The structural and electromagnetic shielding properties of NBR rubber filled with magnetite (Fe3O4) were studied. Rubber composite materials with ore magnetite and synthetic magnetite have been produced separately in order to observe its differences. Samples have been fabricated using a rubber mill and different magnetite ratios. Also, carbon black was added in the same ratio in all samples, not only to improve the mechanical properties of the composites, but also to enhance its dielectric permittivity and reduce its electric resistivity. This kind of composites are used for the manufacture of electronic elements and especially for the production of electromagnetic shielding materials in both passive defense and civil construction applications; buildings, vehicles or airplanes. FESEM-FIB micrographs of the fillers showed the differences in size and shape of the fillers, which influenced the distribution of the particles inside the matrix and therefore the final properties of the composite. Elemental distribution imaging of the composites exhibited the formation of both synthetic magnetite and carbon black aggregates, these structures affect the samples resistivity and the electromagnetic losses due to the conductivity at high frequencies. Electromagnetic shielding properties of the composites were measured in the X-band (8−12 GHz) and K-band of frequency (18–26.5 GHz), all samples showed attenuations greater than −26 dB in both frequency bands. Peaks of maximum attenuation and wider bandwidths were found in the K-band due to the electronic polarization that increased the permittivity of the samples at this high frequency band. The magnetite source (mineral or artificial), its ratio in the rubber matrix and the composite thickness determined the electromagnetic properties of the composite materials.

With the aim to produce a material with magnetic and semiconductor properties, a lanthanide bismuth-ferrite type material is proposed in this work. Polycrystalline samples of Dy2Bi2Fe4O12 were produced following the standard solid-state reaction method. Structural characterization through the X-ray diffraction technique evidences that the synthesized ceramic crystallizes in a perovskite-like orthorhombic structure, belonging to the Pnma (#62) space group. Scanning electron microscopy images revealed the granular nature of the samples with mean grain sizes of nanometric order. X-ray energy dispersion spectra allowed establishing that in the samples there are no elements different from those expected in the stoichiometric proportions suggested by the chemical formula of the compound. Studies of electrical behavior were carried out using I–V curves and electrical permittivity as a function of frequency and temperature, which show the diode varistor feature of this material with a marked Maxwell–Wagner-type trend. The semiconductor band gap was determined from the analysis of diffuse reflectance spectra that reveal Eg = 1.88 eV. Temperature-dependent magnetization curves for applied fields of 1.0, 5.0 and 10 kOe showed the behavior expected for ferromagnetic type materials, with strong evidence of magnetic frustration causing irreversibility in curves obtained from Zero Field Cooling and Field Cooled measurement procedures. The magnetization hysteresis curves at temperatures of 50, 200 and 300 K exhibit a ferromagnetic response with evidence of superparamagnetic effects due to the significant presence of nano-sized ferromagnetic grains. Based on the obtained results, it can be affirmed that the material behaves like a soft ferrimagnetic semiconductor with low coercive field (between 500 Oe and 700 Oe) and remnant magnetization (between 2.15 × 10−4 emu/g and 3.25 × 10−4 emu/g) that would have eventual technological implications in the spintronic industry.

In this work a study of the synthesis process, crystal structure and magnetic behavior of gadolinium manganite with Fe substitutions in Mn positions of GdMn1-xFexO3(x=0, 0.1, 0.2) is reported. The samples were synthetized by the conventional solid-state reaction method. Structural characterization of final compounds was analyzed by Rietveld refinement, which revealed its crystallization in an orthorhombic symmetry belonging to the Pbnm (No. 62) space group. Results reveal that aand ccell parameters and the unit cell volume increase, while the lattice parameter band the cell volume decrease with Fe substitution. The main effect in the structure is related to oxygen positions, i.e. in the octahedral distortions and rotations. DC susceptibility measurements, in the temperature regime between 4 K and 300 K on the application of an external field of 200 Oe, show a paramagnetic feature at high temperatures for all xstudied values, with magnetic transitions associated to a magnetic ordered state at low temperatures (21.8 K < T < 25.2 K). Meanwhile, a ferrimagnetic transition is detected for x=0.1close to T=30.7 K.In order to explain the appearance of ferrimagnetism for this configuration, a model is suggested where an imbalance in the magnetic structure of GdMnO3(type-Aantiferromagnetic) generated due to the introducing a Fe3+ion in each pair consecutive unit cells is proposed. Theeffective magnetic moment obtained agrees to the reported value for the material with x=0.0, confirming the ferrimagnetic behavior for this concentration of Fe3+in the structure.

Polycrystalline samples of Sm2Bi2Fe4O12 were produced by the standard solid state reaction method. The structural characterization revealed that the material crystallizes in an orthorhombic structure (Pnma # 62 space group). Scanning electron microscopic images showed granular and densified characteristics on the surface and inside the samples, with two well-differentiated grain sizes: micrometric and submicrometric. From energy-dispersive X-ray spectra, it was established that the samples contained the expected elements in stoichiometric proportions suggested by the chemical formula of the compound. I–V curves and measurements of electrical permittivity as a function of temperature showed semiconductor-type behaviors, strongly dependent on the polycrystalline character of the material and a Maxwell–Wagner-type dielectric tendency. The optical spectral analysis corroborated the semiconductor behavior with the optical bandgap Eg = 2.62 eV. Temperature-dependent magnetization results have the expected form for ferromagnetic-type materials, with evidence of disorder that gives rise to magnetic irreversibility between the zero-field cooling and field cooling measurement procedures. Magnetization curves as a function of the applied field showed a hysterical response, even at room temperature, revealing the occurrence of ferromagnetic ordering in the material. The ab initio calculations of the electron density of states reveal the appearance of a mean semiconductor band gap whose value is in agreement with that measured experimentally. The effective magnetic moment is attributed to the majority contributions of the 3d-Fe orbitals. At low temperatures, the behaviors of the specific heat at constant volume and pressure are similar, with a tendency of the former towards the Dulong–Petit limit. Strong changes in all the thermophysical properties studied are evident due to the effects of pressure and temperature on the wave behavior of the crystal lattice. At higher temperatures, a strong variation in the Debye temperature induces divergence in thermophysical parameters for different applied pressures. The physical parameters related to the coexistence of the semiconductor and ferromagnetic properties in the material suggest possible technological implications in the spintronics industry.

The Z-type Sr3Co2Fe24O41 hexaferrite constitutes a family of relatively new materials, which offers potential technological applications in the spintronics industry due to its magnetoelectric properties at room temperature. In this work, synthesis of the Sr3Co2Fe24O41 material following both citrate and Pechini methods is reported. X-ray diffraction patterns evidence that the obtained samples crystallize in hexagonal structures, belonging to the P63/mmc (#194) space group. Micrographs of scanning electron microscopy reveal the hexagonal characteristic of grains in the homogeneous and strongly densified surface. Measurements of magnetization as a function of applied fields show the ferromagnetic hysteretic behavior of material. Low-temperature curves of susceptibility (50 K T > TC). A drastic change in the thermogravimetric curve at T = 683 K is attributed to the loss of magnetic force caused by the transition between ferromagnetic and paramagnetic states.

A careful experimental and theoretical study of the double perovskite type material Ba2YSbO6 is reported. The results show that this yttrium-based antimoniate oxide crystallizes in a cubic structure, Fm3¯m (#225) space group, with evidence of the cationic ordering that characterizes a rocksalt superstructure, and tolerance factor slightly less than the unit (τ = 0.9791) due to the size differences between the Y-O6 and Sb-O6 octahedrons. The magnetic response shows weak ferromagnetic effects for the temperature values studied (50, 200 and 300 K), with evidence of an antiferromagnetic reentrance at T = 118 K under the application of low magnetic fields, which is attributed to the presence of polar ordering, accompanied by octahedral distortions caused by the movement of the cations Y3+ and Sb5+, whose effects are no longer observed in the presence of a fairly high external magnetic field (of the Tesla order). The results of the optical characterization by diffuse reflectance suggest the occurrence of a band gap Eg = 4.61 eV, which is characteristic of an insulating material. The electronic structure calculations corroborate the insulating nature of the Ba2YSBO6 complex perovskite. The results allow classifying this material as a Mott insulator, in which the occurrence of intra-site spin-exchange facilitates unpaired spins to the 4d-t2g Yttrium states, mediated by the 2p Oxygen orbitals and 5p Antimony orbitals, resulting in the ferromagnetic character of the insulating material. Keywords: Antimoniate yttrium-based perovskite, Structural characterization, Magnetic response, Optical band gap, Electronic structure

Double perovskite-like material Sr2TiMoO6 (STMO) has been obtained by solid state synthesis. Analysis of the morphology by SEM reveals the occurrence of polyhedral grains with octahedral forms in its faces and hexahedron forms in the corners. The electronic structure and thermophysical properties are reported for the first time using the pseudopotential and plane-wave method. Theoretical calculations for different antiferromagnetic configurations showed that the antiferromagnetic spins alignment in planes interspersed along the direction [111] presents the most stable structure. Values of the coefficient of thermal expansion, the Debye temperature, and the Gruneisen parameter show that at low temperatures the specific heat at constant pressure and constant volume has a similar behavior, with a value for the Dulong-Petit limit expected for a triclinic perovskite-type structure. Finally, measures of susceptibility as a function of temperature suggest an antiferromagnetic behavior, with Neel temperature TN = 20.1 K. From the Curie-Weiss adjust, the temperature independent susceptibility was determined to be χo = 0.0038 emu/mol and the effective magnetic moment μ = Peff = μB = 1.30 μB.

En este artículo reportamos la síntesis y caracterización estructural del sistema RE3Ba5Cu8O18 (RE = Dy, Gd, Ho, Sm, Y, Yb), lo que viene a complementar lo ya reportado por Aliabadi, et al., quienes lograron una temperatura crítica (TC) de ∼ 100 K para el sistema superconductor Y3Ba5Cu8O18, y evaluó la respuesta estructural en una muestra. El nuevo sistema RE3Ba5Cu8O18 se obtuvo utilizando el método de reacción de estado sólido seguido de un proceso térmico similar al empleado para el superconductor RE: 123. Asimismo, los resultados experimentales obtenidos mediante la técnica de difracción de rayos X y el análisis de Rietveld evidenciaron que estas muestras tenían la estructura cristalina esperada; sin embargo, fue obvio que la presencia de fases no superconductoras no afectó la temperatura de transición superconductora. Además, los estudios magnéticos revelaron que las muestras de RE3Ba5Cu8O18 registraban una transición superconductora en el rango de 80 a 93 K dependiendo de la tierra rara. In this paper, we report the synthesis and structural characterization of the RE3Ba5Cu8O18 (RE = Dy, Gd, Ho, Sm, Y, Yb) system, which adds to the findings reported by Aliabadi, et al., who determined a critical temperature (TC) of ∼ 100 K for the superconducting Y3Ba5Cu8O18 system and evaluated its structural response in a sample. The new RE3Ba5Cu8O18 system was produced using the solidstate reaction method and a similar thermal process as the one used for the superconductor RE: 123. The experimental results obtained with X-ray diffraction and the Rietveld analysis showed that these samples had the expected crystal structure. However, it was obvious that the presence of non-superconducting phases did not affect the superconducting transition temperature. Moreover, magnetic studies revealed that RE3Ba5Cu8O18 samples showed a superconductivity transition within a temperature range of 80 - 93 K depending on the rare earth.

Perovskite-like materials which include magnetic elements have relevance due to the technological perspectives in the spintronics industry. In this work, the magnetic, structural and electronic properties of the Ba2CoMoO6 double perovskite are investigated. Calculations are carried out through the Full-Potential Linear Augmented Plane Wave method within the framework of the Density Functional Theory with exchange and correlation effects in the Generalized Gradient and Local Density approximations, including spin polarization. From the minimization of energy as a function of volume using the Murnaghan’s state equation the equilibrium lattice parameter and cohesive properties of this compound were obtained. The study of the electronic structure was based in the analysis of the electronic density of states, and the band structure, showing that this compound evidences a conductive character for a spin channel and insulation for the other, and presents an integer value for the effective magnetic moment (3.0 μB), which allows it to be classified as a half-metallic material. The effects of pressure and temperature on thermophysical properties such as specific heat, Debye temperature, coefficient of thermal expansion and the Grüneisen parameter were calculated and analyzed from the state equation of the system. The obtained results reveal that, in the low temperature regime, the specific heat at constant volume and pressure presents an analogous behavior to each other, with a tendency to the limit of Dulong-Petit typical of the structures of cubic perovskite type, showing a value of 246.3 J/mol.K at constant volume and slightly higher values at constant pressure. The dependence of the coefficient of thermal expansion, the temperature of Debye and the Grüneisen parameter with the increase in temperature is discussed in relation to other perovskite-like materials. Los materiales de tipo perovskita que incluyen elementos magnéticos tienen relevancia debido a las perspectivas tecnológicas en la industria de la espintrónica. En este trabajo se efectúa un estudio exhaustivo de las propiedades magnéticas, estructurales y electrónicas de la perovskita doble Ba2CoMoO6. Los cálculos se realizan a través del método de ondas planas aumentadas y linealizadas dentro del marco de la teoría del funcional de la densidad con efectos de intercambio y correlación en las aproximaciones del gradiente generalizado y de densidad local, incluyendo polarización de espín. A partir de la minimización de la energía en función del volumen, utilizando la ecuación de estado de Murnaghan, se obtuvieron el parámetro de red de equilibrio y las propiedades cohesivas de este compuesto. El estudio de la estructura electrónica se basó en el análisis de la densidad electrónica de estados y la estructura de bandas, mostrando que este compuesto evidencia un carácter conductor para un canal de espín y aislante para el otro, presentando un valor entero para el momento magnético efectivo (3.0 μB), que permite clasificarlo como un material espín-metálico. Los efectos de la presión y la temperatura sobre las propiedades termofísicas, como el calor específico, la temperatura de Debye, el coeficiente de expansión térmica y el parámetro Grüneisen, se calcularon y analizaron a partir de la ecuación de estado del sistema. Los resultados obtenidos revelan que, en el régimen de baja temperatura, el calor específico a volumen y presión constantes presenta un comportamiento análogo entre sí, con una tendencia al límite de Dulong-Petit típico de las estructuras de tipo perovskita cúbica, mostrando un valor de 246.3 J/mol.K a volumen constante y valores ligeramente más altos a presión constante. La dependencia del coeficiente de expansión térmica, la temperatura de Debye y el parámetro Grüneisen con el aumento de temperatura se discute en relación con otros materiales de tipo perovskita. Fil: Deluque Toro, Crispulo Enrique. Universidad del Magdalena; Colombia Fil: Gil Rebaza, Arles Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Grupo de Estudio de Materiales y Dispositivos Electrónicos; Argentina Fil: Villa Hernández, Jorge I.. Universidad Nacional de Colombia; Colombia Fil: Landinez Téllez, David A.. Universidad Nacional de Colombia; Colombia Fil: Roa Rojas, Jairo. Universidad Nacional de Colombia; Colombia

The monophasic polycrystalline ceramic perovskite-based Eu2Bi2Fe4O12 was synthesized by the solid-state reaction method. X-ray diffraction measurements in the Bragg–Brentano geometry and Rietveld analysis reveal that this material crystallizes in an orthorhombic structure with Pnma (#62) space group. Average grain size of 450 nm is calculated of a log-normal distribution and obtained by means scanning electron microscopy images. Results from magnetization, pyroelectric and complex impedance measurements as a function of temperature (50 K up to 300 K) show the occurrence of dielectric and magnetic relaxation process starting simultaneously at 112.8 K. The tendency of real and imaginary curves of the dielectric permittivity at temperatures close to room temperature has also shown strong ac conductivity contributions attributed to porosity effects. The magnetization hysteresis loop at room temperature confirms that this new perovskite-based material has a ferromagnetic response. Signature of superparamagnetism effects is also observed as a consequence of the nanometric grain size. Thermostimulated current measurements as a function of temperature reveal the occurrence of ferroelectric polarization for the temperature regime below T = 112.8 K. Diffuse reflectance experiments permitted to establish the semiconductor nature of this material at room temperature with an energy gap of 2.65 eV.

Sr2HoRuO6 ceramic has been synthesized and its structural, morphological, magnetic, optical, and electronic properties studied. Rietveld refinement of x-ray diffraction patterns revealed that this oxide material crystallizes in monoclinic perovskite structure in space group P2 1 /n (no. 14). Scanning electron microscopy revealed polycrystalline surface morphology. x-Ray dispersive spectroscopy suggested that Sr2HoRuO6 was obtained with expected stoichiometry. Magnetic susceptibility curves as a function of temperature revealed ferrimagnetic feature of this material below the Neel temperature TN of 14 K. Evidence of magnetic disorder was provided by the irreversibility observed in the zero-field-cooled and field-cooled responses of the susceptibility below Tirr = 169 K. Analysis of the diffuse reflectance spectrum suggested that this material behaves as a semiconductor with energy gap Eg of 1.38 eV. Results of band structure and density-of-states calculations are in agreement with the interpretation of Sr2HoRuO6 as a semiconductor. The ferrimagnetic behavior is interpreted as due to exchange mechanisms of d–f (Ru–O–Ho) electrons. The effective magnetic moment calculated from density functional theory was 93.5% of the experimental value obtained from Curie–Weiss fitting of the susceptibility curve.

The possible low temperature biferroic feature of Eu2Bi2Fe4O12 complex perovskites was recently reported. The aim of this work is to present a theoretical study of the structural, magnetic, electronic and ferroelectric properties of this material. Several energy minimization processes were performed for three types of cationic distributions, different angles of rotation, octahedral inclination, and some kinds of magnetic ordering. The results reveal that the most stable crystallographic arrangement corresponds to an intercalated distribution of the Eu3+ and Bi3+ cations between the FeO6 octahedra. Similarly, energy is minimized for rotations and octahedral inclinations corresponding to angles θe = 12.86° and ϕe = 13.32°, respectively. With respect to the distribution of magnetic moments, the results reveal that a G-type antiferromagnetic configuration is the most energetically favorable. The electronic structure is studied from ab initio calculations following the formalism of density functional theory and the pseudopotential plane wave method. In this formalism, the exchange and correlation mechanisms are described by means of the generalized gradient approach (GGA + U), considering spin polarization. The ferroelectric characteristic is analysed by determining ferroelectric polarization based on the calculation of the Berry phase. The theoretical results obtained are consistent with the experimental reports, which is why the Eu2Bi2Fe4O12 material is expected to exhibit biferroic behavior at low temperatures, because the Berry phase introduces hybridizations between the 3d-Fe and 2p-O states that favor the occurrence of Dzyaloshinskii-Moriya interactions, which facilitate the occurrence of ferroelectricity coexisting with weak ferromagnetism. An extensive study of the thermodynamic properties in the presence and absence of the Berry phase is undertaken by means of the Debye quasi harmonic model. The specific heat difference with and without the Berry phase reveals the occurrence of a ferroelectric transition at T = 113 K without the application of external pressure. When the applied pressure is incremented, a systematic increase in the transition temperature is observed due to the reduction of overlap between the 3d-Fe orbitals and the 2p-O orbitals in the compressed octahedra of perovskite.

Resumen Este trabajo describe la producción y caracterización magnética de un compuesto a base de resina epoxi y caucho pulverizado reforzado con magnetita (Fe 3 O 4 ) en polvo. Además, se presenta el análisis realizado a los compuestos en función de la carga magnética dentro de la matriz polimérica. Las propiedades magnéticas del material se realizaron a diferentes temperaturas en un rango magnético de -30000 a 30000 0e. La morfología tanto de los precursores como de los compuestos fue determinada por microscopía electrónica de barrido (MEB) y la caracterización estructural fue realizada por difracción de rayos X (DRX). El patrón de difracción obtenido en las mediciones de DRX permite observar que, con la adición de magnetita en polvo en la matriz plástica, se crea una transición amorfo-cristalina en el material. A través de las imágenes obtenidas por MEB se observa la presencia de hematita en el precursor (Fe 3 O 4 ) y un tamaño irregular en las muestras. Los compuestos se comportan como un material magnético blando y presenta cambios en la variación de la fuerza coercitiva, tanto con el incremento de temperatura como con la variación de porcentaje de volumen de magnetita en la matriz polimérica. El material fabricado puede ser utilizado en aplicaciones donde el compuesto debe ser fácilmente detectable. Abstract This work describes the production and magnetic characterization of a compound base on epoxy resin and powdered rubber reinforced with magnetite (Fe 3 O 4 ) poder. Also it is presented the análisis carried out on the components, which are according to the magnetic charging inside the polymeric matrix. the magnetic properties of the material they were made at different temperaturas in a magnetic range from -30000 to 30000 Oe the morphology of both the precursons like the compounds was determined by scanning electron microscopy and structural characterizatin was performed by X- ray diffraction (XRD). The diffraction pattern obtained in the XRD measurements allows us to observe that, with the addition of powdered magnetite in the plastic matrix, an amorphous-crystalline transition is created in the material. Through the images obtained by SEM, the presence of hematite in the precursor (Fe 3 O 4 ) and irregular size in the samples is observed. The compounds behave like a soft magnetic material and present changes in the variation of the coercive force, both with the increase in temperature and with the percentage variation of magnetite volume in the polymer matrix. The manufactured material can be used in applications where the compound should be easily detectable.

This work presents a rapid and facile method to produce and adjust the magnetic and physical properties of magnetic nanoparticles. SEM and DRX characterizations, as well as magnetic hysteresis curves and magnetic susceptibility curves, were performed to study changes in the nanoparticles as a function of two stirring speeds: 1000 and 3000 rpm. The formation of spherical nanoparticles was observed at both speeds, but the small ones (72 nm) were obtained at the highest stirring speed. However, at this speed, the magnetite nanoparticles showed to be partially oxidized to hematite. Magnetic curves reveal the superparamagnetic and spin-glass behavior of both kinds of nanoparticles. The blocking and irreversibility temperature of the nanoparticles was not perceived even at room temperature.

In the search for new materials with applicable magnetic properties in spintronic devices, the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La2CoFeO6 using the modified Pechini route; the experimental study of structural, morphological and magnetic properties, and the analysis of the electronic structure and bands are obtained in the framework of the Density Functional Theory. Rietveld refinement of experimental X-ray diffraction patterns revealed the crystallization of this oxide material in a perovskite-like monoclinic structure, space group [Formula: see text]21/[Formula: see text] (# 14). Scanning electron microscopy and atomic force microscopy images revealed that the surface morphology is essentially polycrystalline, with mean grain sizes between 177 and 188 nm. The dispersive X-ray spectroscopy suggests that the material obtained contains La, Fe, Co and O in the stoichiometric proportions expected by up to 98%. The magnetic susceptibility curves as a function of temperature indicated that the material is ordered ferromagnetically, showing strong irreversibility effects due to the disorder of the Fe and Co cations in the three crystallographic directions of the structure and to the strong distortions in the FeO6 and CoO6 octahedra. Magnetic hysteresis curves confirmed the ferromagnetic character of the material for all temperatures evaluated, up to room temperature. I–V response curves revealed a semiconductor-like behavior with a figure of merit exponent 1.53 of the varistor type. The ferromagnetic semiconductor behavior suggests the potential applicability of the material in spintronic technological devices.

The triple perovskite with formula La2SrFe2CoO9 has been synthesized and experimentally studied. The samples were obtained by the solid-state reaction method. Scanning Electron Microscopy images show a strongly diffused granular surface morphology with mean grain size of 1 μm and Electron Dispersive X-ray spectra evidence that the chemical composition of sample is in good agreement with the nominal values of the stoichiometric formula. The electrical transfer functions were studied through the Impedance Spectroscopy technique in the range from 1 mHz to 100 KHz and in the temperature, range from 75 to 295 K. The interpretation of BODE and NYQUIST - diagrams allows the development of an equivalent circuit which explain the behavior of the electrical response throughout the frequency range. The conductance measurements showed the dependence of the conduction mechanisms with frequency and temperature. Structural and impedance properties are correlated allowing to propose mechanisms of charge transfer.

The synthesis process of the polycrystalline ceramic compound Nd2SrMn2TiO9 by means of the solid-state reaction procedure is reported. The crystalline structure was analyzed through X-ray diffraction experiments in the Bragg–Brentano recipe. The Rietveld refinement of the diffraction pattern by using the GSAS code shows that this material crystallizes in an orthorhombic structure, space group Pnma (#62), with lattice parameters a = 5.4764(6) Ǻ, b = 7.7468(6) Ǻ, and 5.4810(6) Ǻ. The surface morphology was studied by scanning electron microscopy images, which evidence the formation and compacting of grain with mean size 352.63 nm. Semiquantitative compositional analysis performed by means of Energy Dispersive X-ray Spectroscopy shows the stoichiometric composition of the samples. Measurements of magnetization as a function of temperature reveal that this compound has a ferromagnetic behavior. The analysis with the Curie equation permitted to establish an effective magnetic moment μeff = 4.33 μB, which is 95.7% in agreement with the theoretical value expected from the Hund's rules. Measurements of DC resistivity as a function of temperature show a conductor behavior below the Curie temperature and insulator above. Evidences of a nonlinear response as a function of frequency with high values of relative dielectric constant reveal the occurrence of giant dielectric constant with ϵr = 6480 for ν = 100 Hz.

En el presente trabajo se utilizó el código Wien2k, en el marco de la teoría del funcional de la densidad de Kohn-Sham, aplicando el método de ondas planas aumentadas y linealizadas (full-potential linearized augmented plane wave, FP- LAPW) y adoptando la aproximación de gradiente generalizado (GGA) de Perdew, Burke y Ernzerhof para la energía de intercambio y correlación, así como la aproximación de densidad local (local density approximation, LDA) para el cálculo de la densidad de estados y la estructura de bandas de la perovskita doble Sr2HoNbO6. Para los cálculos se consideró el grupo Fmm (#225), experimentalmente obtenido a partir de mediciones de difracción de rayos X y del método de refinamiento de Rietveld. El parámetro de red experimental fue de 8.018 Å, el cual concuerda en un 99,2 % con las predicciones teóricas efectuadas a partir de la minimización de la energía mediante la ecuación de estado de Murnaghan. A partir de mediciones de susceptibilidad magnética en función de la temperatura y del ajuste con la ley de Curie, se obtuvo el valor del momento magnético efectivo 10,01 μB. Este valor es muy cercano del esperado teóricamente a partir de las reglas de Hund (10,60 μB). La brecha de energía determinada entre las bandas de valencia y de conducción fue de 3,3 eV, lo que revela el carácter aislante de la perovskita compleja Sr2HoNbO6 para la configuración de espín hacia arriba, en tanto que se observó el carácter semiconductor para la polarización de espín hacia abajo, con una brecha de energía de 0,77 eV. Las propiedades termodinámicas se calcularon a partir de la ecuación de estado usando el modelo cuasi-armónico de Debye. Un comportamiento del calor específico, con CV≈CP, se encontró a temperaturas inferiores a T = 500 K, con valores del límite de Dulong-Petit que doblaban los que se han reportado para materiales del tipo de la perovskita. In this work we used the Wien2k code, within the framework of the Kohn-Sham Density Functional Theory (DFT), applying the Full-Potential Linearized Augmented Plane Wave method (FP-LAPW) and adopting the Generalized Gradient approximation (GGA) for the exchange-correlation energy due to Perdew, Burke, and Ernzerhof, as well as the Local Density approximation (LDA) for the calculation of the Density of States and band structure of the Sr2HoNbO6 double perovskite. For calculations, we considered the Fmm (#225) space group, which was experimentally obtained from X-ray diffraction measurements and Rietveld refinement. The experimental lattice parameter was 8.018 Å, which is 99.2% in agreement with the theoretical prediction from the minimization of energy through the Murnaghan state equation. From the measurements of magnetic susceptibility as a function of temperature and the adjustment with the Curie law, we obtained a value for the effective magnetic moment of 10.01 μB, which is close to the theoretical expected from Hund’s Rule (10.60 μB). An energy gap of 3.3 eV between the valence band and the conduction band revealed the insulator character of the Sr2HoNbO6 complex perovskite for the spin up configuration, but a semiconductor feature was observed for the spin down polarization, with an energy gap of 0.77 eV. The thermodynamic properties were calculated from the state equation by using the Debye quasiharmonic model. A specific heat behavior of CV≈CP was found at temperatures below T = 500 K, with Dulong-Petit limit values doubling those reported for perovskite materials.

Perovskite-like materials, which include magnetic elements, have relevance because their technological perspectives of applications in the spintronics industry. In this work, the magnetic, structural, electronic and thermodynamic properties of the Ba2TiMnO6 of the perovskite-like manganite are investigated. Calculations are carried out through the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations, including spin polarization. From the minimization of energy as a function of volume using the Murnaghan’s state equation the equilibrium lattice parameter and cohesive properties of this compound were obtained. The study of the electronic structure was based in the analysis of the electronic density of states (DOS), and the band structure, showing that this compound evidences an effective magnetic moment of 3.0 µB. The pressure and temperature dependence of specific heat, entropy, thermal expansion coefficient, Debye temperature and Grüneisen parameter were calculated by DFT from the state equation using the quasi-harmonic model of Debye. A specific heat behavior CV≈CP was found at temperatures below T = 400 K, with Dulong-Petit limit values, which are quite higher than those, reported for simple perovskites. Resumen Los materiales de tipo perovskita que incluyen elementos magnéticos son relevantes debido a sus perspectivas de aplicabilidad tecnológica en la industria de la espintrónica. En este trabajo fueron investigadas las propiedades magnéticas, estructurales, electrónicas y termodinámicas de la manganita de tipo perovskita Ba2TiMnO6. Los cálculos fueron realizados a través del método del potencial de ondas planas aumentadas y linealizadas (FP-LAPW), en el marco de la Teoría del Funcional Densidad (DFT), con efectos de intercambio y correlación en las aproximaciones de gradiente generalizado (GGA) y de densidad local (LDA), incluyendo polarización de espín. A partir de la minimización de la energía en función del volumen, usando la ecuación de estado de Murnaghan se obtuvieron los parámetros de equilibrio de la red las propiedades de cohesión de este compuesto. El estudio de la estructura electrónica se basó en el análisis de la densidad de estados (DOS) y la estructura de bandas, mostrando que este compuesto evidencia un momento magnético efectivo de 3.0 µB. la dependencia con la temperatura y la presión del calor específico, la entropía, el coeficiente de expansión térmica, la temperatura de Debye y el parámetro de Grüneisen fueron calculados mediante DFT a partir de la ecuación de estado, usando el modelo cuasi-armónico de Debye. Se encontró que el calor específico CV≈CP para temperaturas por debajo de T = 400 K, con un límite de Dulong-Petit relativamente mayor que el reportado para perovskitas simples.

We report first-principles calculations of the elastic properties, electronic structure and magnetic behavior performed over the Ba2NiMoO6 double perovskite. Calculations are carried out through the full-potential linear augmented plane-wave method within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient and Local Density Approximations, including spin polarization. The elastic properties calculated are bulk modulus (B), the elastic constants (C11, C12 and C44), the Zener anisotropy factor (A), the isotropic shear modulus (G), the Young modulus (Y) and the Poisson ratio (υ). Structural parameters, total energies and cohesive properties of the perovskite are studied by means of minimization of internal parameters with the Murnaghan equation, where the structural parameters are in good agreement with experimental data. Furthermore, we have explored different antiferromagnetic configurations in order to describe the magnetic ground state of this compound. The pressure and temperature dependence of specific heat, thermal expansion coefficient, Debye temperature and Grüneisen parameter were calculated by DFT from the state equation using the quasi-harmonic model of Debye. A specific heat behavior CV ≈ CP was found at temperatures below T = 400 K, with Dulong?Petit limit values, which is higher than those, reported for simple perovskites. Fil: Deluque Toro, Crispulo Enrique. Universidad del Magdalena; Colombia Fil: Mosquera Polo, A. S.. Universidad Nacional de Colombia; Colombia Fil: Gil Rebaza, Arles Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina Fil: Landínez Téllez, D. A.. Universidad Nacional de Colombia; Colombia Fil: Roa Rojas, J.. Universidad Nacional de Colombia; Colombia

La caracterización de nanoburbujas de oxígeno en soluciones de NaCl ha sido efectuda con el objeto de estudiar la variación de su tamaño, concentración, pH, temperatura y niveles de agregación, a través de procesos de saturación de oxígeno y cavitación para diferentes tiempos. Las nanoburbujas fueron producidas mediante la inyección de oxígeno por rotación a la solución salina en un medio difusivo, a temperatura constante, en la procura de una solución con distribución homogénea. La solución finalmente obtenida fue sometida a varias pruebas, a varios tiempos diferentes, para observar los cambios en las nanoburbujas. La caracterización del tamaño de las nanoburbujas en la solución fue llevada a cabo utilizando la técnica de dispersión dinámica de la luz. La concentración de la solución se determinó mediante un proceso semicuantitativo teniendo en cuenta la concentración de partículas estándar y la tasa de conteo por segundo del dispositivo. Se midió el potencial ζ para establecer los niveles de agregación y estabilidad de las nanoburbujas a diferentes temperaturas y pH. A una temperatura T=4 oC, se observó que el diámetro de las nanoburbujas permanece aproximadamente constante en el tiempo (1000 to 2000 nm), independientemente de los valores de pH, alcanzándose la mayor estabilidad de las nanoburbujas. The characterization of oxygen nanobubbles in NaCl solutions has been performed in order to study the variation of their size, concentration, pH, temperature and aggregation levels, through oxygen saturation and cavitation processes for different times. The nanobubbles were produced by the injection of oxygen by rotation to the saline solution in a diffusive medium, at constant temperature, in the way of searching for a solution with homogeneous distribution. The solution finally obtained was subjected to several tests at different times to observe changes in the nanobubbles. The size characterization of nanobubbles in the solution was performed using the dynamic light scattering technique. The concentration of the solution was determined by a semi-quantitative process taking into account the concentration of standard particles and the counting rate per second of the device. Potential ζ was measured in order to establish the aggregation and stability levels of the nanobubbles at different temperatures and pHs. At a temperature T=4 oC the diameter of the nanobubbles remains approximately constant in time (1000 to 2000 nm), regardless of the pH values, and the highest stability of nanobubbles is reached.

1 recurso en línea (páginas 51-61)., We report structural analysis, surface morphology, magnetic ordering, dielectric response, optical feature and the electronic structure of the Dy2BiFeO6 novel complex perovskite. The samples were produced by the standard solid-state reaction recipe. Crystallographic analysis was performed by Rietveld refinement of experimental X-ray diffraction patterns. Results show that this material crystallizes in a perovskite with orthorhombic structure, which corresponds to the Pnma (#62) space group. From the Curie-Weiss fitting on the curve of susceptibility as a function of temperature we establish that the ordering corresponds to a paramagnetic-antiferromagnetic transition, with a Weiss temperature θ=-18,5 K, which is compatible with the behavior of the inverse of susceptibility as a function of temperature, and a Néel temperatura TN=50,8 K. The Curie constant allowed for us to obtain an effective magnetic moment of 15,7 μB. The result of magnetization as a function of the applied field, measured at T=50 K, shows a magnetic hysteresis behavior that corroborate the magnetic ordering present for this temperature value. Measurements of the dielectric constant as a function of applied frequencies at room temperature give as a result a high relative dielectric constant (ε=780). The reflectance curve as a function of the wavelength reveals the typical behavior of a double perovskite-like material and permits to obtain the energy gap 2,74 eV, which is characteristic of a semiconductor material., En este trabajo reportamos el análisis estructural, morfología superficial, ordenamiento magnético, respuesta dieléctrica y característica óptica de la nueva perovskita compleja Dy2BiFeO6. Las muestras fueron producidas mediante reacción de estado sólido. El análisis cristalográfico fue realizado a través de refinamiento Rietveld de los patrones experimentales de rayos X. Los resultados muestran que este material cristaliza en una perovskita ortorrómbica correspondiente al grupo espacial Pnma (#62). Por medio del ajuste de Curie-Weiss a la respuesta de la susceptibilidad magnética en función de la temperatura se estableció que el ordenamiento magnético se relaciona con una transición paramagnético-antiferromagnético con una temperatura de Weiss θ=-18,5 K, la cual es acorde con el comportamiento del inverso de la susceptibilidad en función de la temperatura, y una temperatura de Néel TN=50,8 K. La constante de Curie permitió determinar un momento magnético efectivo de 15,7 μB. Medidas de magnetización en función del campo aplicado a T=50 K, muestran un débil comportamiento histerético, que corrobora el ordenamiento magnético presente a esa temperatura. Mediciones de la constante dieléctrica en función de la frecuencia aplicada a temperatura ambiente dan como resultado una alta constante dieléctrica relativa a bajas frecuencias (ε=780). La curva de reflectancia en función de la longitud de onda revela el comportamiento típico de un material de tipo perovskita doble y permite la obtención de la brecha de energía de 2,74 eV característico de un material semiconductor., Bibliografía: páginas 60-61.

This paper reports the production of YBa $$_{2}$$ Cu $$_{3-x}$$ Fe $$_{x}$$ O $$_{7-\delta }$$ (0.05 $$\le x$$ $$\le $$ 0.12) superconducting system by using the standard solid-state reaction technique. A Rietveld refinement of the experimental X-ray diffraction patterns allows the determination of the lattice parameters and the phase composition of the studied system; the mean present phase shown is an orthorhombic phase Pmmm. Magnetic and transport properties are typical for superconducting samples. In this paper, magnetic susceptibility fluctuations are studied in the limit of weak magnetic fields. For each of the samples, the best fit of the experimental data of $$\Delta \chi $$ /T, in the limit of weak magnetic fields in function of the reduced temperature, allowed us to obtain the values of $$A_\mathrm{s}$$ (diamagnetism of Schmidt) and $$B_\mathrm{LD}$$ (LD parameter). The Lawrence–Doniach model (LD) has been used for the fluctuation analysis. It is demonstrated, by means of the analysis of the thermal fluctuations, that the YBa $$_{2}$$ Cu $$_{3-x}$$ Fe $$_{x}$$ O $$_{7-\delta }$$ system has an excellent 2D scaling behavior (BLD).

In this work, we report the synthesis of the Ba $$_{2}$$ DySbO $$_{6}$$ new double perovskite by means of the solid-state reaction recipe from high-purity oxide powders of BaCO $$_{3}$$ , Dy $$_{2}$$ O $$_{3}$$ , and Sb $$_{2}$$ O $$_{5}$$ . The analysis of the crystal structure was carried out through the X-ray diffraction technique with posterior Rietveld refinement of the experimental diffraction data by the GSAS code. Results reveal that the Ba $$_{2}$$ DySbO $$_{6}$$ material crystallizes in a rhombohedral perovskite structure, belonging to the R-3 (#148) space group with lattice parameter a = 5.96260(5) A, and angle $$\alpha $$ = 60.008 $$^{\circ }$$ . The magnetic characterization was performed by measurements of magnetic susceptibility as a function of temperature. The behavior observed in the temperature regime from 4 K up to 300 K was paramagnetic. The characteristic magnetic parameters were obtained from the fitting with the Curie equation, obtaining the values of susceptibility independent of temperature 0.00633 emu/mol and effective magnetic moment 8.9 $$\upmu _\mathrm{{B}}$$ , which is 84 % in agreement with the expected value predicted by the Hund’s rules. The electronic structure was calculated by means of linearized augmented plane waves in the framework of the density functional theory (DFT). This study considers the cohesion energies as a function of the lattice parameter, with a lattice constant a, whose value is 98 % in agreement with the experimental result. Curves of density of states as a function of the wave number reveal that this material behaves as an insulator with energy gap 3.65 eV. This result was corroborated by diffuse reflectance experiments adjusted to the Kubelka–Munk equation. The effective magnetic moment obtained from the DFT calculations was $$7.7\,\upmu _\mathrm{{B}}$$ .

Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr{sub 2}GdCu{sub 2}O{sub 8}. • We synthesized the doped compound Rui{sub x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}, for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y} ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr{sub 2}GdRu{sub 1−x}Re{sub x}O{sub y}, which represents amore » new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO{sub 2} (magnetic) and CuO{sub 2} (superconductor) sub-lattices can clearly be observed.« less