TATIANE DA SILVA NASCIMENTO

TATIANE DA SILVA NASCIMENTO

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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.
Determination of Si content in Fe-doped HfSiO4 nanoparticles by neutron activation analysis
2017 - SALES, T.S.N.; BOSCH-SANTOS, B.; SAIKI, M.; PEREIRA, L.F.; CARBONARI, A.W.; SAXENA, R.N.; BURIMOVA, A.
New synthesis method of Fe-doped hafnium silicate nanoparticles (NPs) with tetragonal structure is reported. The procedure implies auto-controlled incorporation of Si from the quartz to the iron-doped hafnium oxide NPs. X-ray diffraction data has shown that lattice parameters of Fe-HfSiO4 thus obtained are very close to those previously known for hafnon. It was established that the hafnon-like phase has stabilized at T=1173K which is ~500K lower than the corresponding transition of bare bulk hafnium silicate. The fractions of Si and Fe in the composite matrix were evaluated via neutron activation analysis (NAA). Delayed gamma NAA results 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 throughout the formation of hafnon-like phase; (iii) Fe-doped hafnium oxide has taken as much Si from the quartz as was needed for the arrangement of Fe1-x-Hf x SiO4 tetragonal system. Our results are consistent with those observed for similar materials, such as metal (Fe,V) doped zircon, where metal has also demonstrated catalytic effect on phase stabilization.
A study on possible gamma ray interferences from 60mCo, 139Ba and 56Mn formed in the direct thermal neutron irradiation of LaBaCo2O6 e LaBaMn2O6 perovskites to produce 140La(140Ce) probe nuclei for PAC spectroscopy
2017 - BOSCH-SANTOS, B.; SAIKI, M.; NASCIMENTO, N.M.; SILVA, D.S.; SALES, T.S.N.; PEREIRA, L.F.D.; CARBONARI, A.W.
In this work, a method to introduce radioactive 140La nuclei with a half-life (t1/2) of 40.8 h, into samples of LaBaTM2O6 (TM = Mn, Co) double perovskites is described to carry out perturbed gamma-gamma angular correlation (PAC) spectroscopy measurements using 140La(140Ce) as probe nuclei. There are several methods to insert this probe nucleus in the samples and the present paper presents a new methodology to obtain the 140La(140Ce) in the compounds. These compounds were submitted to short irradiations with thermal neutrons in the rabbit station of IEA-R1 nuclear reactor of the IPEN/CNEN-SP. This method could be used because natural La is present in samples. Natural La contains the 139La isotope which, when irradiated with neutrons produces the 140La radioisotope, the parent radioisotope of 140Ce used for PAC measurements. However, other elements present in the compounds are also activated, in particular the isotopes 56Mn, 139Ba and 60mCo. In order to verify if these radioisotopes are presents in the PAC measurements, the gamma ray spectra of these irradiated samples can be measured at different decays times using a high resolution HPGe spectrometer. Samples were irradiated with thermal neutrons for 3 minutes. After short irradiation, the gamma ray spectra were acquired, one hour, 18 h, 24 h and 48 h after irradiation. The gamma ray energies of 328.8 keV and 487.0 keV of 140La (measured in the PAC spectroscopy) can be identified. Besides this, gamma-rays peaks of 56Mn (Eγ of 847.3 and 1812.9 keV and t1/2 of 2.57 h), 139Ba (Eγ of 166.04 keV and t1/2 of 84.63 min) and 60mCo (Eγ of 58.75 and 1333.30 keV and t1/2 of 10.47 min) are identified too. The results indicate that PAC measurements can be started after at least 48 h of decay time when there is in interference of other radioisotopes.