57Fe Mossbauer effect studies of ErFe11Ti and ErFe11TiH compounds

Ferromagnetic compounds ErFe11TiHx (x = 0, 1) have been investigated by Fe-57 Mossbauer spectroscopy in the temperature range 20-300 K. Mossbauer spectra were analyzed in terms of a model which takes into account the local environment of Fe atoms on three crystallographic sites (8f, 8j and 8i) and an influence of the random distribution of titanium on the 8i site. The 14 sextets with different intensities have been considered. The temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from experimental spectra. The hyperfine fields and the isomer shift increasing upon hydrogenation are discussed in terms of the hydrogen-induced Wigner-Seitz unit cell expansion and the s-electrons transfer from Fe atoms to the adjacent hydrogen atoms.