https://doi.org/10.1007/PL00011119
Interplay of structural, magnetic and transport properties in the layered Co-based perovskite LnBaCo2O5 (Ln = Tb, Dy, Ho)
1
Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI,
Switzerland
2
Institut Laue Langevin, 6, rue Jules Horowitz, BP 156X, 38042
Grenoble Cedex 9, France
3
Laboratoire CRISMAT/ISMRA, boulevard du Maréchal Juin,
14050 Caen Cedex, France
4
Laboratoire Léon Brillouin, CE-Saclay, 91191
Gif-sur-Yvette, France
5
Laboratory for Neutron Scattering, Paul Scherrer
Institut, 5232 Villigen PSI, Switzerland
Corresponding author: a fauth@esrf.fr
Received:
13
December
2000
Published online: 15 May 2001
The oxygen deficient cobaltites LnBaCo2O5 (Ln = Tb,
Dy, Ho) exhibit two successive crystallographic transitions at 340 K
and at
210 K. Whereas the first transition (P4/mmm to
Pmmm) is related to the long-range antiferromagnetic ordering of the Co ions
(spin ordering), the second transition (Pmmm to Pmmb) corresponds
to the long-range ordering of the Co2+ and Co3+ species (charge
ordering) occurring in 1:1 ratio in the structure. The charge ordered (CO)
state was directly evidenced by the observation of additional superstructure
peaks using neutron and electron diffraction techniques. The CO state was also
confirmed indirectly from refinement of high resolution neutron diffraction
data as well as from resistivity and DSC measurements. From the refined
saturated magnetic moment values only, ~3.7
and
~2.7
, the electronic configuration of the Co ions in
LnBaCo2O5 remains conjectural. Two pictures, with Co3+ ions
either in intermediate spin state (
) or in high spin state
(
), describe equally well our experimental data. In both
cases, the observed magnetic structure can be explained using the qualitative
Goodenough-Kanamori rules for superexchange. Finally, in contrast to the parent
Ln = Y compound [Vogt et al. , Phys. Rev. Lett. 84, 2969 (2000)], we do
not report any spin transition in
LnBaCo2O5 (Ln = Tb, Dy, Ho).
PACS: 61.12.-q – Neutron diffraction and scattering / 71.30.+h – Metal-insulator transitions and other electronic transitions / 75.50.Ee – Antiferromagnetics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001