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Artigo IPEN-doc 26868 Effects of an external magnetic field on the hyperfine parameters in RE2O3 (RE = Gd, Er) nanoparticles measured by perturbed angular correlation spectroscopy2020 - CORREA, E.L.; BOSCH-SANTOS, B.; SAXENA, R.N.; CABRERA-PASCA, G.A.; CARBONARI, A.W.In order to understand the interaction mechanisms in RE2O3 (RE=Gd, Er) nanoparticles (NPs), Perturbed Angular Correlation (PAC) spectroscopy, a local technique, plus external magnetic field, was used to elucidate local interactions and possible mapping of the different contribution in these compounds. NPs were synthesized by thermal decomposition and characterized by transmission electron microscopy and X-ray diffraction. PAC measurements were performed using 111In(111Cd) as probe nuclei, with and without the application of an external magnetic field (EMF) of 0.5 T in different temperatures (50 K, 100 K, 200 K, 300 K). Results show that the hyperfine magnetic field is almost zero when the probe is located at the symmetric site, and ∼4 T and ∼5 T for Gd2O3 and Er2O3, respectively, when the probe occupies the asymmetric field.Artigo IPEN-doc 26867 Effect of the magnetic impurity on the charge diffusion in highly dilute Ce doped LaMnO32020 - CABRERA-PASCA, G.A.; BOSCH-SANTOS, B.; BURIMOVA, A.; CORREA, E.L.; CARBONARI, A.W.LaMnO3+δ is a complex oxide, which, depending on the oxygen excess concentration, presents different crystalline structure and interesting magnetic and electric properties such as colossal magnetoresistance, polaron dynamics, multiferroic behavior, and charge-orbital ordering. This complexity requires different characterization techniques to draw a picture as complete as possible allowing a good understanding of these phenomena. Here, we have used the perturbed angular correlation (PAC) technique to measure hyperfine interactions at La and Mn sites of LaMnO3+δ(δ ∼0.15) using 140Ce and 111Cd at La sites as probe nuclei in order to investigate within an atomic scale the magnetic and electric interactions in this compound. The results show that 111Cd nuclei occupy highly symmetric local sites in agreement with a rhombohedral structure. The magnetic hyperfine field (Bhf ) measured with 111Cd at La sites is very small (Bhf = 0.40 T) due to the supertransferred magnetic field from Mn neighbors through oxygen orbitals. On the other hand, 140Ce nuclei at La sites present a saturation field of around 3.7 T much higher than that expected for La sites (due to the weak transfer field by superexchange mechanism). In addition, for temperature range above the magnetic ordering (200-300 K) a dynamic hyperfine interaction was observed characterized by the attenuation parameter λ(T) whose temperature dependence allowed to determine the activation energy (Ea) associated to charge transfer. The polarization of the 4f -electron of Ce impurities affects the local magnetic field at impurity sites as well as the Ea.Artigo IPEN-doc 26466 Magnetic field at Ce impurities in La sites of La0.5Ba0.5MnO3 double perovskites2019 - 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.