TATIANE DA SILVA NASCIMENTO

TATIANE DA SILVA NASCIMENTO

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Cobalt doping effects in zinc oxide
2024 - PEREIRA, LUCIANO F.D.; FERREIRA, WANDERSON L.; CORREA, BRUNO S.; COSTA, MESSIAS S.; COSTA, CLEIDILANE S.; FILHO, ARNALDO A.M.; SALES, TATIANE S.N.; BOSCH-SANTOS, BRIANNA; SCHELL, JULIANA; BURIMOVA, ANASTASIA; SAXENA, RAJENDRA N.; CABRERA-PASCA, GABRIEL A.; CARBONARI, ARTUR W.
In this paper, we investigate the solubility effects of Co in ZnO (Zn1−xCoxO, where x = 0, 0.03, 0.05, 0.1, 0.2, 0.25, 0.4, 0.8, and 1) by combining the results of perturbed angular correlation (PAC) spectroscopy using highly diluted 111Cd as probe nuclei and ab initio calculations based on spin-density functional theory (SDFT). This combined approach enables us to characterize the local structure around Cd ions, where, through PAC technique, it was possible to measure the EFG as a function of temperature and Co concentration and thereby monitor the changes in the structure and the Co solubility threshold in ZnO and the ZnO/CoO/Co3O4 mixed phase. The full-potential linear augmented plane wave plus local orbital (APW+lo) formalism were used here to describe the electronic structure of the supercells, including the atomic relaxations. These Ab initio calculations show an interesting behavior of the Cd and Co impurity levels in the band structure of ZnO, which explains the experimental results in terms of the origin of EFG and the evidence of ferromagnetic response.
Cd impurities in Vanadium oxides
2021 - BURIMOVA, ANASTASIA; LEITE NETO, OSMAR F.; BOSCH-SANTOS, BRIANNA; CORREA, EDUARDO L.; PEREIRA, LUCIANO F.D.; SALES, TATIANE S.N.; RIBEIRO JUNIOR, IBERE S.; COSTA, MESSIAS S.; COSTA, CLEIDILANE; DANG, THANH T.; ZYABKIN, DMITRY; VAN STIPHOUT, KOEN K.F.; GERAMI, ADELEH M.; CORREIA, JOAO M.; SCHELL, JULIANA; CARBONARI, ARTUR W.
The number of metastable phases, the capriciousness at changing external conditions, and lack of accurate description of local behavior already resulted in severe misinterpretation of experimental outcomes for vanadium oxides[1–3]. The scope of already implemented and potential applications of vanadium oxides is, indeed, impressive, particularly as a battery cathode for energy storage[ 4]. Doping is widely exploited as a means of application-oriented tuning of the material properties. The properties of each particular phase may be tuned by doping to satisfy specific requirements and/or improve the functional performance. In the work here reported, electric quadrupole interaction on 111mCd nuclei implanted in vanadium pentaoxide doped with different concentrations of Cd were measured with time-differential perturbed angular correlations (TDPAC). Pure V2O5 as well as doped with 1%, 5%, and 10% of Cd were measured at different temperatures. To correlate the results with the possible formation of different phases and compounds, samples of VO2, CdV2O6, and Cd2V2O7 were also measured. The intention is to provide a comprehensive description, at an atomic level, of the doping effects on the local crystal structure and the electronic structure around the impurity and the consequences on the properties of the host oxides. Preliminary results show that the probability of formation of cadmium vanadates is low but the temperature and atmosphere of measurements have an important effect on the local scale.
Magnetic and structural properties of the intermetallic Ce(1−x)LaxCrGe3 series of compounds
2021 - BOSCH-SANTOS, B.; CABRERA-PASCA, G.A.; CORREA, E.L.; CORREA, B.S.; SALES, T.N.S.; MOON, K-W.; DENNIS, C.L.; HUANG, Q.; LEAO, J.B.; LYNN, J.W.; CARBONARI, A.W.
The Ce(1−x)LaxCrGe3 (x = 0, 0.19, 0.43, 0.58, and 1) intermetallic compound system has been investigated by magnetization measurements and neutron scattering techniques to determine the effect of La doping on the magnetic ordering and exchange interaction between Cr ions. The structural and magnetic characterization in this series was first verified by x-ray diffraction and bulk magnetization measurements. The samples exhibit the known hexagonal perovskite structure (P63/mmc space group) and have a single magnetic phase according to magnetizationmeasurements. In this paper, the ferromagnetic ordering temperature for Cr evolves smoothly from a range of 68 K to 77 K for CeCrGe3 to a range of 91 K to 96 K for LaCrGe3 as La replaces Ce. Magnetization results indicate the formation of domain walls below the transition temperature for all Ce(1−x)LaxCrGe3 systems investigated. Neutron results indicate ordered magnetic Cr moments aligned along the c axis for the x = 1 LaCrGe3 system, as well as for x = 0.19, 0.43, and 0.58, which contrasts with the x = 0 CeCrGe3 where the moments order in the ab plane.
Study of hyperfine interactions in Perovskite structure CaTiO3 with perturbed angular correlation spectroscopy
2019 - LEITE NETO, O.F.S.; SANTOS, B.S.; NARESSI, A.L.E.; SALES, T.S.N.; SAXENA, R.N.; CARBONARI, A.W.
Ceramic materials of the perovkista were identified as candidates for immobilization of medium and high levels of radioactive waste due to the fact that they are thermodynamically chemically and physically stable. Because it is a nuclear technique, PAC spectroscopy has great precision and efficiency in the measurement of local hyperfine fields on an atomic scale, constituting an ideal tool for the investigation of the atomic origin of structural phenomena, such as the influence of defects in the macroscopic properties of many materials or the local neighborhood of metallic atoms in the oxide structure. The samples has been prepared by sol-gel method and characterized by X-ray diffraction. In this study the time differential perturbed angular correlation (PAC) spectroscopy was used to study the structure of CaTiO3 and the possible defects made by radiation exposure. The probe nucleus used in this research was 111Cd. The PAC method is based on the hyperfine interaction of nuclear moments of the probe with extra nuclear magnetic fields or electric field gradients (EFGs). In the case of quadrupolar electric interaction, the experimental measurement gives the quadrupolar frequency νQ with respective distribution δ as well as the asymmetry parameter η of EFG. The γ-γ PAC measurements were carried out using a standard set up with four conical BaF2 detector scintillators with a time resolution of 0.6 ns (FWHM).
Local inspection of magnetic properties in GdMnIn by measuring hyperfine interactions
2021 - CABRERA-PASCA, G.A.; MAGNO, J.F.; FERREIRA, W.L.; CAMPOS, A.C.; BOSCH-SANTOS, B.; SALES, T.S.N.; PEREIRA, L.F.D.; BURIMOVA, A.; SAXENA, R.N.; FREITAS, R.S.; CARBONARI, A.W.
GdMnIn is reported to crystallize in the hexagonal MgNi2-type structure presenting a spin-glass behavior with no magnetic order attributed to the triangular spin frustration of magnetic ions. In the present work, FC-ZFC magnetization, specific heat and AC susceptibility measurements along with the local magnetic exchange measured by hyperfine interactions at In sites are used to investigate the magnetic behavior in GdMnIn compound. The ZFC-FC magnetization curves exhibit an inflection which was ascribed to the antiferromagnetic transition at TN= 145 K. These curves also give an indication of thermomagnetic irreversibility at 118 K, which along with the absence of inflection in specific heat results might be associated to spin-glass behavior. Results of AC susceptibility and magnetic hyperfine field measured using 111In(111Cd) probe nuclei carried out by perturbed angular correlations (PAC) technique did not show evidence of spin-glass behavior. The thermomagnetic irreversibility in FC-ZFC curves along with results of hyerfine interactions suggest the presence of magneto-crystalline anisotropy effects and a weak long-range coupling in GdMnIn.
RE-doped Fe3O4 (RE = Eu, Gd, Er) nanoparticles for nanothermometry
2019 - CORREA, E.; BOSCH-SANTOS, B.; SALES, T.; CABRERA-PASCA, G.; CORREA, B.S.; NETO, O.F.; CARBONARI, A.W.; OLESHKO, V.; DENNIS, C.
Temperature affects every physical system, chemical reaction, and biological process. A new method, magnetic nanothermometry, is being explored to measure temperature throughout a volume. This method uses large changes in magnetization as function of temperature, which cannot be obtained with current magnetic nano-objects (MNO). To get a large magnetization change we have examined the magnetic properties of RE-doped Fe3O4 (RE = Eu, Gd, Er) MNO. Samples were synthesized by co-precipitation. For the doped material, RE+3 were chosen in order to replace the Fe+3 in the (Fe+2)(Fe+3)2O4 structure. Structural characterization was performed by X-ray diffraction and transmission electron microscopy. Hyperfine interaction parameters as a function of temperature (300 K to 873 K) were obtained by perturbed angular g-g correlation (PAC) spectroscopy using 111In(111Cd) as probe nuclei. To fit the PAC spectra, the 111Cd probes were considered to occupy three sites: tetrahedral, octahedral, and a third site where the probes are located at the nanoparticle surface [1]. The hyperfine magnetic field Bhf was calculated using the Larmor equation, and its behavior as a function of temperature follows a Brillouin-type transition. For example, the Curie temperature (TC) obtained for 5% Er-doped was approx. 846 K (FIG. 1), which is higher than the expected TC for pure Fe3O4 (approx. 722 K) [2]. Magnetization as a function of temperature shows a 70 % change in magnetization around 100 K for Er-doped Fe3O4 (FIG.2), which is an improvement in temperature on pure Fe3O4 (below 50 K) [3]. Current work is focused on correlating the temperature range in which the magnetization change occurs and determining if it depends on the dopant element.
Magnetic field at Ce impurities in La sites of LaBaMn2O6 double perovskites
2019 - BOSCH-SANTOS, B.; NASCIMENTO, N.; SAIKI, M.; CORREA, E.L.; SALES, T.S.; PEREIRA, L.F.; CABRERA-PASCA, G.A.; CARBONARI, A.W.
Magnetic behavior in LaBaMn2O6 double perovskite compounds has been investigated with various techniques, due to the rich variety of electromagnetic properties, such as a colossal magnetoresistance, charge and orbital ordering, and metal-insulator transition. In this paper, we have used a nuclear and short-range technique, the Perturbed Angular Correlation (PAC) spectroscopy, to investigate the magnetic hyperfine field at the 140Ce nucleus of Ce impurities occupying La sites. The radioactive 140La nuclei with a half-life of 40.8 h were produced by direct activation of natural La present in the samples through the irradiation with neutrons in the IEA-R1 nuclear research reactor of IPEN. The PAC measurements were carried out with a six BaF2 detector spectrometer at several temperatures between 10 K and 400 K. This double perovskite samples were synthesized by sol-gel route. The crystal structure was determined by X-ray diffraction and the analyses showed that this method produced perovskite oxides with cubic structure in Pm-3m space group. This phase occurs due to an oxygen deficiency. The local properties investigated by PAC spectroscopy revealed a ferromagnetic transition temperature above 300 K and an anomalous behavior of the temperature dependence of magnetic hyperfine field at La sites, which can be ascribed to the contribution of 4f band of Ce to Bhf at low temperatures due to the increase in its localized character.
Magnetic field at Ce impurities in La sites of La0.5Ba0.5MnO3 double perovskites
2019 - BOSCH-SANTOS, B.; NASCIMENTO, N.M.; SAIKI, M.; CORREA, E.L.; SALES, T.S.N.; PEREIRA, L.F.D.; CABRERA-PASCA, G.A.; SAXENA, R.N.; SCHELL, J.; CARBONARI, A.W.
Due to its rich variety of electromagnetic properties, such as a colossal magnetoresistance, charge and orbital ordering, and metal-insulator transition, the magnetic behavior in La0.5Ba0.5MnO3 double perovskite compounds has been investigated by several techniques, however more experimental data, especially from atomic resolution techniques, are still necessary to understand such complex behavior. In this paper, we have used a nuclear and short-range technique, the Perturbed Angular Correlation (PAC) spectroscopy, to investigate the magnetic hyperfine interaction at the 140Ce and 111Cd probe nuclei as impurities occupying La sites. This double perovskite samples were synthesized by Sol- Gel route. The crystal structure was determined by X-ray diffraction and the analyses showed that this method produced perovskite oxides with cubic structure in Pm-3m space group and the homogeneity was determined by Transmission Electron Microscopy (TEM). The local properties investigated by PAC spectroscopy revealed a ferromagnetic transition temperature above 300 K and a pure antiferromagnetic interaction below 100 K. Moreover, it also indicates an anomalous behavior of the temperature dependence of magnetic hyperfine field at La sites measured with 140Ce probe nuclei, which can be ascribed to the contribution of 4f band of Ce to Magnetic Hyperfine Field (Bhf) at low temperatures due to the increase in its localized character.
Low temperature synthesis of pure and Fe-doped HfSiO4: Determination of Si and Fe fractions by neutron activation analysis
2019 - SALES, T.N.S.; BOSCH-SANTOS, B.; SAIKI, M.; BURIMOVA, A.; PEREIRA, L.F.D.; SAXENA, R.N.; CARBONARI, A.W.
A new method of synthesis of hafnium silicate HfSiO4 (also known as hafnon) is reported. We observed a selfcontrolled incorporation of SiO2 from the quartz tube in which a sample of hafnium oxide nanoparticles was heated. This approach was then adapted to Fe-doped hafnon production. Sample structure, morphology and composition were characterized by X-ray diffraction, electron microscopy and neutron activation analysis. Diffraction data has shown that lattice parameters of doped HfSiO4 thus obtained are very close to those previously known for bare hafnon. The hafnon-like phase stabilized at T=900 °C which is about 500 °C lower than the corresponding transition of bare bulk hafnium silicate. The fractions of Si and Fe in the composite matrices were determined with neutron activation analysis. These results completed by X-ray diffraction data allowed to assume that (i) Fe initially substituted Hf in the HfO2 lattice; (ii) there was no migration of iron atoms from Hf to Si sites at the formation of hafnon-like phase; (iii) doped and undoped hafnium oxide has taken as much Si from the quartz as was needed for the arrangement of Fe1-xHfxSiO4 tetragonal system, 0≤x<0.2. Our results are consistent with those obtained for similar materials, such as metal (Fe,V) doped zircon, where the dopant also demonstrated catalytic effect on phase stabilization.
Tuning the dielectric response of HfO 2 nanoparticles by Si-doping
2018 - SALES, T.S.N.; BURIMOVA, A.; CARBONARI, A.W.; BOSCH-SANTOS, B.; PEREIRA, L.F.D.
The properties of bulk materials and corresponding nanostructures may differ significantly which leads to distinct scopes of their applications. As the miniaturization continues, nanostructures show great potential in microelectronics. Among others, nanostructured hafnium (IV) oxide (hafnia, HfO 2 ) has attracted considerable attention due to its chemical stability and physical characteristics 1 . It has high dielectric constant ( ∼ 25) and is relatively thermally stable (melting point at 3085 K) 2 . These qualities have made hafnia an alternative to SiO 2 for gate oxide layers in field-effect transistors, since the leakage current issue and consequent thickness limitations of silica were hindering miniaturization. Clearly, the features of HfO 2 can be further tuned by doping 3 . Understanding the relation between the macro-properties of such complex systems and their architecture at atomic scale should help select doping parameters adequate for particular applications. In this work 0at%, 5at% and 10at% Si-doped HfO 2 nanoparticles (NPs) were synthesized via sol-gel method. Basic characterization included scanning/transmission electron microscopy, electron backscattering and X-ray diffraction. NPs were demonstrated to have spherical shape, sizes in the range of 10─40nm and monoclinic structure (m-HfO 2 ). Local structure and electronic environment of the samples was probed with perturbed angular correlation (PAC) spectroscopy. Sample irradiation resulted in the formation of 181 Hf isotopes (PAC probes 4 ) at several sites whose decay to 181 Ta is preferentially through an intermediate (metastable) state with lifetime depending strongly on local extra-nuclear fields. Thus, time distribution of decay probability provided information on the ambient of the probe. For undoped sample PAC data has revealed two distinct Hf sites, one of those possessing well-defined quadrupole frequency ν Q ≈ 750 MHz and electric field distribution asymmetry η ≈ 0.36. Site occupation raised with temperature from 16% at T = 473K to 75% at T = 1073K, which agrees with the results found in the literature for the quadrupole interactions of 181 Ta in m-HfO 2 4 . For the doped samples (both Si 5at% and 10at%) additional site was observed. Symmetrical electric field distribution ( η = 0) and a greater site fraction at T = 673─873K allowed to attribute it to a tetragonal phase of hafnia. First principles analysis has shown that doping m-HfO 2 with certain cations can induce the formation of tetragonal phase 5 . We emphasize that this phase is desirable for transistor applications since it is associated with the highest dielectric constant.