Eur. Phys. J. B 21, 163-174 (2001)
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

Abstract

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).