Effect of band filling and structural distortions on the Curie temperature of Fe-Mo double perovskites

Abstract

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 θFe−O−Mo in both series. In contrast, the mean bond-distance d (Fe,Mo)−O 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.

Unusual electron-doping effects inSr2−xLaxFeMoO6Saitoh1, Nakatake2, Nakajima3 et al. 2005Phys. Rev. B192130View full textAdd to dashboardCite

“…Namely, the doped electrons are mainly introduced into the Mo 4d t 2g states, as inferred by Moritomo et al 4 More recently, Frontera et al have observed by neutron diffraction that the Mo−O distance increases with La doping while the Fe−O one does not change. 20 In terms of the ionic-radius argument, this implies that the doped electrons will mainly be located at the Mo sites, 20 in agreement with the above argument. On the other hand, the spectral weight at the feature B of x=0.2 is also considerably enhanced in the high photon energies despite the fact that the two curves are virtually identical below 120 eV.…”

Evidence of kinetic-energy-driven antiferromagnetism in double perovskites: A first-principles study of La-dopedSr2FeMoO6

“…The crystal structure of La-doped Sr 2 FeMoO 6 on the other hand is controversial. Some of the study 38,39 reports that though I4/mmm symmetry is retained for small doping of La, for doping beyond x = 0.4 or so, the symmetry changes to P2 1 /n. The other measurements 30 however reports that all compounds of Sr 2−x La x FeMoO 6 for x = 0, 0.25, 0.5 and 1.0 crystallize in I4/mmm symmetry.…”

Cerámicas magnetorresistivas. Progresos recientes: desde el entendimiento básico a las aplicaciones

“…Extensive neutron diffraction experiments have allowed to determine that the mean <Fe(Mo)-O> distance expands upon La 3+ substitution. This is just what one should expect from carrier injection into the antibonding Fe-O-Mo orbitals [23,24]. Recent photoemission experiments have also confirmed that the density of states at the Fermi level increases with the La content [25].…”