A5078416073- Magnetic and transport properties of perovskites and related materials
- ZnO doping and properties
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Phase-change materials and chalcogenides
- Solid-state spectroscopy and crystallography
- Semiconductor Quantum Structures and Devices
- Magnetism in coordination complexes
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Rare-earth and actinide compounds
- Magneto-Optical Properties and Applications
- GaN-based semiconductor devices and materials
- Chalcogenide Semiconductor Thin Films
- Organic and Molecular Conductors Research
- Quantum and electron transport phenomena
- Copper-based nanomaterials and applications
- Iron-based superconductors research
- Pulsars and Gravitational Waves Research
- Semiconductor materials and devices
- Characterization and Applications of Magnetic Nanoparticles
- Advanced Chemical Physics Studies
- Metal and Thin Film Mechanics
Universidade de São Paulo
2015-2024
Université de Montpellier
1996-1999
Concordia University
1997
We have investigated the low-temperature T field-induced ordering in ${\mathrm{NiCl}}_{2}\ensuremath{\cdot}4\mathrm{SC}({\mathrm{NH}}_{2}{)}_{2},$ from magnetization measurements. This is an $S=1$ system with a large single-ion uniaxial anisotropy leaving singlet ground state. An external magnetic field $(\mathbf{B})$ parallel to symmetry axis induces antiferromagnetically ordered phase for ${B}_{c1}<B<{B}_{c2}.$ The establishment of this long-range order can be regarded as Bose-Einstein...
Here we present a status report of the Schenberg antenna. In past three years it has gone to radical upgrading operation, in which have been installing 1K pot dilution refrigerator, cabling and amplifiers for nine transducer circuits, designing new suspension vibration isolation system microstrip antennas, developing full set transducers, oscillators. We are also studying an innovative approach, could transform into broadband gravitational wave detector.
The present study reports the successful synthesis of Sn1–xCrxO2 nanoparticles with doping content (x) ranging from 0 to 0.20. Samples were synthesized by a polymer precursor method using SnCl2·H2O and Cr(NO3)3·5H2O as metal ion suppliers. In all samples X-ray diffraction data show one single-phase formation (rutile-type), crystalline size (crystal strain) decreasing (increasing) monotonically while increasing x content, which are assigned substitutional solution Cr Sn ions in structure....
Magnetization steps from ${\mathrm{Mn}}^{2+}$ pairs in several single crystals of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{O}$ $(0.0056<~x<~0.030),$ and one powder $(x=0.029),$ were observed. They used to determine the four largest exchange constants (largest $J$'s), single-ion axial anisotropy parameter D. The two constants, ${J}_{1}{/k}_{\mathrm{B}}=\ensuremath{-}18.2\ifmmode\pm\else\textpm\fi{}0.5\mathrm{K}$...
Here we present a status report of the first spherical antenna project equipped with set parametric transducers for gravitational detection. The Mario Schenberg, as it is called, started its commissioning phase at Physics Institute University São Paulo, in September 2006, under full support FAPESP. We have been testing three preliminary transducer systems order to prepare detector next cryogenic run, when will be calibrated. are also developing sapphire oscillators that replace current ones...
Mixtures of 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (F4BImNN) and 2-(benzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (BImNN) crystallize as solid solutions (alloys) across a wide range binary compositions. (F4BImNN)(x)(BImNN)((1-x)) with x < 0.8 gives orthorhombic unit cells, while ≥ 0.9 monoclinic cells. In all crystalline samples, the dominant intermolecular packing is controlled by one-dimensional...
In this report we present a systematic structural and magnetic analysis of Co-doped ZnO nanoparticles prepared via microwave-assisted hydrothermal route. The data confirm the incorporation Co ions into wurtzite lattice concentration mainly near/at surface nanoparticles. This spatial distribution is set to passivate nanoparticles, inhibiting nanoparticle growth suppressing observation ferromagnetic phase. Based on experimental theoretical results propose kinetic-thermodynamic model for...
Magnetization measurements were performed on five ${\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Eu}}_{x}\mathrm{S}$ samples, with $0.0092<~x<~0.059$. Two of the samples measured at 20 mK in magnetic fields $\mathbf{H}$ up to 50 kOe parallel $[111]$ and $[100]$ directions. The other three 0.6 K 180 kOe. data exhibit magnetization steps (MST's) arising from pairs. These MST's depend direction H, so that anisotropic interactions must be included analysis. lead a value...
Rare-earth nitrides, such as gadolinium nitride (GdN), have great potential for spintronic devices due to their unique magnetic and electronic properties. GdN has a large moment, low coercitivity, strong spin polarization suitable transistors, memories, spin-based quantum computing devices. Its splitting of the optical band-gap functions filter that offers means spin-polarized current injection into metals, superconductors, topological insulators, two-dimensional layers, other novel...
X-band (9.56 GHz) electron paramagnetic resonance (EPR) measurements were performed on ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Yb}}_{\mathit{x}}$S, ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Yb}}_{\mathit{x}}$Se, and ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Yb}}_{\mathit{x}}$Te samples (x\ensuremath{\sim}0.5--2 %) at liquid-helium temperatures to study hyperfine transitions, estimate the value of effective Land\'e factor g...
The field-induced antiferromagnetic phase transitions in NiCl24SC(NH2)2 have been determined fields up to 18 T and temperatures down 0.016 K. This is an S=1 system with a singlet ground state separated from excited doublet by D/kB. In zero field this spin-gap remains nonmagnetic T=0, because the small exchange interaction (J) “subcritical” (2zJ&lt;D). However, magnetic applied along uniaxial direction lowers one of energy levels, thus creating condition for establishment long-range...
Composites of magnetite nanoparticles encapsulated with polymers attract interest for many applications, especially as theragnostic agents magnetic hyperthermia, drug delivery, and resonance imaging. In this work, were synthesized by coprecipitation different (Eudragit S100, Pluronic F68, Maltodextrin, surfactants) nano spray drying technique, which can produce powders from solutions or suspensions. Transmission scanning electron microscopy images showed that the bare have 10.5 nm, after...
Electron paramagnetic resonance (EPR) experiments were performed on a ${\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Ce}}_{x}\mathrm{Se}$ crystal at liquid-helium temperatures and show very clearly that the doublet ${\ensuremath{\Gamma}}_{7}$ is ground state for cerium ions. The cubic symmetry shown effective Land\'e factor ${\mathrm{Ce}}^{3+}$ determined to be $1.354\ifmmode\pm\else\textpm\fi{}0.003.$ An orbital reduction introduced explain $g$ experimental value. High-field magnetization...
Electron paramagnetic resonance experiments were performed on ${\mathrm{Bi}}_{2(1\mathrm{\ensuremath{-}}\mathrm{x})}$${\mathrm{Gd}}_{2\mathrm{x}}$${\mathrm{Se}}_{3}$ and ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Gd}}_{\mathrm{x}}$Se samples at room liquid-helium temperatures. The ${\mathrm{Gd}}^{3+}$ sites are characterized by hexagonal octahedral symmetries in samples, respectively. absolute signs of the spin-Hamiltonian parameters determined comparing intensities lines...
The magnetization of Sn1-x Eux Te, with x= 0.011 and 0.042, was measured at 20 mK in magnetic fields up to 90 kOe. Magnetization steps (MSTs) from pairs triplets were observed. MSTs give J /kB = -0.311±0.006 K for the dominant Eu-Eu exchange constant. Comparisons curves numerical simulations indicate that, instead being distributed randomly, Eu ions tend bunch together. A phenomenological approach which uses concept a local concentration xL is quite successful describing data these two samples.
Abstract Cobalt ferrite nanocrystals (CoFe 2 O 4 ) were synthesized by means of ultrasonic agitation and afterward subjected to different annealing temperatures. The structural morphological properties the investigated X‐ray diffraction scanning electron microscopy. results showed that samples composed CoFe monophase nanocrystals. particle size increased with increasing Infrared spectroscopy magnetization exhibited usual features Superparamagnetism was not observed at room temperature....
We demonstrate that light resonant with the band gap forces antiferromagnetic semiconductor EuSe to enter ferromagnetic alignment in picosecond timescale. A photon generates an electron-hole pair, whose electron forms a supergiant spin polaron of magnetic moment nearly 6000 Bohr magnetons. By increasing intensity, whole illuminated region can be fully magnetized. The key novel large photoinduced magnetization mechanism is huge enhancement susceptibility when both and interactions are present...
The Mario Schenberg gravitational wave detector has started its commissioning phase at the Physics Institute of University Sao Paulo. We have collected almost 200 h data from instrument in order to check out behavior and performance. also been developing a acquisition system for it under VXI System. Such is composed an analog-to-digital converter GPS receiver time synchronization. building software that controls sets up acquisition. Here we present overview system, some results first run...