RESUMO
Using an intense negative muon (µ^{-}) source, we have studied the internal magnetic fields in a powder sample of magnesium hydride (MgH_{2}). By extracting the signal from the µ^{-} captured on Mg nuclei, we found that the negative muon spin rotation and relaxation (µ^{-}SR) spectra clearly showed a Kubo-Toyabe-type relaxation, which indicates a random magnetic field at the Mg site. The field distribution width obtained is very consistent with the predicted value at the Mg site estimated by dipole field calculations, supporting our claim to have observed the nuclear magnetic fields of hydrogens in MgH_{2}. As is the case with µ^{+}SR, µ^{-}SR promises to soon be an indispensable tool for materials analyses.
RESUMO
In-beam Mössbauer spectra of 57Mn implanted into LiAlH4 were measured at different temperatures between 17 and 300 K. The Mössbauer spectrum measured at 17 K showed two sets of doublets, which were assigned to 57Fe atoms at substitutional sites at Al3+ and Li+ sites. The Debye temperatures θM for the 57Fe atoms at Al3+-substituted and Li+-substituted sites were estimated to be 194 K and 117 K, respectively. The assignments were confirmed by density functional theory calculations.