M.L.N. Grillo
Rio de Janeiro State University
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Publication
Featured researches published by M.L.N. Grillo.
Journal of Alloys and Compounds | 1999
R.S. de Biasi; M.L.N. Grillo
Electron spin resonance spectra of manganese-doped strontium oxide have been studied at room temperature for Mn concentrations between 0.10 and 0.40 mol.%. The results suggest that the range of the exchange interaction between Mn2+ ions is about 0.63 nm.
Journal of Physics and Chemistry of Solids | 1996
R.S. de Biasi; M.L.N. Grillo
Abstract The electron spin resonance (ESR) technique was used to investigate the diffusion of Fe 3+ in rutile (TiO 2 ). ESR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation energy for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be E A = 215 kJ mol −1 . This result is consistent with experimental data using the radioactive-tracer sectioning technique and represents an independent measurement of the activation energy for diffusion of trivalent iron in rutile, which is difficult to achieve by other means in this mixed-valence system.
Journal of Alloys and Compounds | 2000
R.S. de Biasi; M.L.N. Grillo
Abstract Electron spin resonance spectra of copper-doped magnesium oxide have been studied at room temperature for Cu concentrations between 0.10 and 0.50 mol%. The results suggest that the range of the exchange interaction between Cu 2+ ions is about 0.60 nm.
Materials Research-ibero-american Journal of Materials | 2012
Ronaldo Sergio De Biasi; M.L.N. Grillo
Electron magnetic resonance (EMR) spectra of Cr3+ ions in samples of chromium-doped strontium titanate (SrTiO3) have been studied at room temperature for chromium concentrations between 0.20 and 1.00 mol%. According to previous studies, chromium substitutes Ti4+ sites in the lattice and its preferred valence state is Cr4+, which is EMR silent in the X-band, but the trivalent state can be produced by illumination or codoping with Nb. In the present work, the codoping method was used; the results show the electron magnetic resonance linewidth of the Cr3+ spectrum increases with increasing chromium concentration and that the range of the exchange interaction between Cr3+ ions is about 0.96 nm.
Journal of Alloys and Compounds | 2000
R.S. de Biasi; M.L.N. Grillo
Abstract The ferromagnetic resonance technique was used to study the annealing behavior of the metallic glass Co 65 Fe 4 Ni 2 Si 15 B 14 (Metglas 2714A). The peak-to-peak FMR linewidth, Δ H pp , was measured at room temperature and 9.5 GHz for three isothermal annealing times in the temperature range 737–757 K. The transformed fraction, as derived from FMR data, satisfies the Johnson–Mehl–Avrami equation with the exponent n between 0.98 and 1.00. The activation energy for crystallization is estimated from the times to Δ H pp =25–35 mT to to be 199 kJ mol −1 .
Journal of Alloys and Compounds | 1998
R.S. de Biasi; M.L.N. Grillo
The ferromagnetic resonance technique was used to study the annealing behavior of the metallic glass Co69Fe4Ni1Mo2B12Si12 (Metglas 2705M). The peak-to-peak FMR linewidth, ΔHpp, was measured at room temperature and 9.5 GHz for three isothermal annealing times in the temperature range 727–767 K. The transformed fraction, as derived from FMR data, satisfies the Johnson–Mehl–Avrami equation with the exponent n between 1.04 and 1.06. The activation energy for crystallization is estimated from the times to ΔHpp=55–65 mT to be 86 kJ mol−1.
Materials Research-ibero-american Journal of Materials | 2015
Ronaldo Sergio De Biasi; M.L.N. Grillo
Electron magnetic resonance (EMR) spectra of gadolinium-doped barium titanate (BaTiO3) have been studied at room temperature for gadolinium concentrations between 0.20 and 2.00 mol%. The results suggest that the Gd3+ ions occupy substitutional sites, replacing the Ba2+ ion, that the electron magnetic resonance linewidth increases with increasing gadolinium concentration, and that the range of the exchange interaction between Gd3+ ions is about 0.98 nm, of the same order as that of the same ion in other host lattices, such as strontium titanate (SrTiO3), strontia (SrO), quicklime (CaO), magnesia (MgO) and zircon (ZrSiO4). The fact that the electron magnetic resonance linewidth of the Gd3+ ion increases, regularly and predictably, with Gd concentration, shows that the Gd3+ ion can be used as a probe to study, rapidly and non-destructively, the crystallinity and degradation of BaTiO3.
Materials Research-ibero-american Journal of Materials | 2014
R.S. de Biasi; M.L.N. Grillo
The electron magnetic resonance (EMR) technique was used to investigate the diffusion of Mn2+ in lime (CaO). The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation energy for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be EA = 266 ± 27 kJ. Mol - 1, about 30% larger than the activation energy for diffusion of Mn2+ in magnesia (MgO), a compound with the same crystal structure. The difference is attributed to the fact that the Ca2+ has a larger ionic radius than Mg2+.
Materials Research Bulletin | 1999
R.S. de Biasi; A. A. R. Fernandes; L. Balinski; M.L.N. Grillo
Electrical resistivity and ferromagnetic measurements were performed on as-received and partially crystallized samples of a commercial metallic glass, Metglas 2605S-3A. As the measurements were performed on the same set of samples, the influence of sample preparation can be discarded and any difference in the results attributed to intrinsic differences between the two methods. The results of the present investigation suggest that both techniques lead essentially to the same results.
Journal of Solid State Chemistry | 2005
R.S. de Biasi; M.L.N. Grillo