LEVY SCALISE MACIEL
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Resumo IPEN-doc 27093 Insights into anomalous magnetic hyperfine field at Ce impurity in LaMn2X2 (X=Si, Ge)2019 - PEREIRA, LUCIANO F.D.; MESTNIK-FILHO, JOSE; CABRERA-PASCA, GABRIEL A.; BOSCH-SANTOS, BRIANNA; FERREIRA, WANDERSON L.; GONÇALVES, VITOR C.; SCALISE, LEVY; GENEZINI, FREDERICO A.; SAXENA, RAJENDRA N.; CARBONARI, ARTUR W.The LaMn2X2 (X=Si, Ge) intermetallic compounds doped with cerium exhibit the interesting physical effects that are typical of the REMn2X2 (RE=rare earth) series (such as magnetocaloric, superconductivy) or are originated from cerium in specific electronic environment (e.g. Kondo, intermediate valence, strongly correlated electron). Recently, the magnetic hyperfine field (mhf) at 140Ce-doped LaMn2(Si(1-x)Gex)2 was determined by perturbed gamma-gamma angular correlation spectroscopy. The 140Ce mhf follow the host magnetization in LaMn2Si2, while in LaMn2(Si(1-x)Gex)2 (with x = 0.2 up to 1), it has anomalous behaviour, which was associated with 4f cerium mhf contribution. In this work, first principles band structure simulations were used to improve the understanding of the distance role (generated by interchange of Si and Ge) on mhf cerium contribution.Resumo IPEN-doc 26773 Study of the local magnetics and electrics properties at Gd2Ti2O7 by PAC spectroscopy and ab initio calculations2019 - CORREA, E.L.; PEREIRA, L.F.; FERREIRA, W.L.; BOSCH-SANTOS, B.; SCALISE, L.; GONÇALVES, V.; SANTOS, R. dos; SCHELL, J.; CARBONARI, A.W.Gd2Ti2O7 exhibits a complex magnetic behavior with a geometrically frustrated antiferromagnetic ordering below TN = 1.1 K and a second magnetic transition at 0.7 K. In the work here reported, perturbed angular correlation (PAC) technique was used in order to measure electric quadrupole hyperfine interactions at 111mCd probe nuclei on Ti sites. These experimental results along with those for magnetic hyperfine interactions at 155Gd previously reported from Mossbauer Effect spectroscopy were interpreted with electronic structure first-principles calculation. Single and doped-Cd cell simulations have been performed with potential linearized augmented plane waves methods and generalized gradient approximation from Perdew-Burke-Ernzerhorf embodied within the WIEN2k all-electron code. PAC measurements have exhibited 111mCd probes occupying two fraction sites characterized by well-defined quadrupole frequencies (as shown in the spin-rotation spectra in the figure) with almost the same values for the corresponding electric field gradient (efg), however, with slightly difference in the asymmetry parameters. Theoretical efg’s obtained for Cadmium atoms located at Gd or Ti sites of the pyrochlore structure indicate that both experimental hyperfine parameters corresponding to Cd at Titanium site.