By means of high resolution neutron powder diffraction at low temperature we
have characterized the structural details of LaxSr2−xFeMoO6
(0≤x≤0.5) and CaxSr2−xFeMoO6 (0≤x≤0.6) series of compounds. This study reveals a similar variation of the mean
bond-angle \FeOMo in both series. In contrast, the mean bond-distance \FeMoO\
increases with La but not with Ca substitution. Both series also present a
different evolution of the Curie temperature (TC), which raises in the La
series and slightly decreases in the Ca one. We thus conclude that the
enhancement of TC in the La series is due to the electron filling of the
conduction band and a concomitant rising of the density of states at the Fermi
level.Comment: Revtex, 4 Journal pages, 2 figures, 1 tabl