A neutron diffraction study of the partial substitution of Ba in the layered cobaltites YBa1−x(Ca,Sr)xCo2O5.5

AURELIO, G.; S¨¢NCHEZ, R. D.; CURIALE, J.; CUELLO, G. J.

Karlsruhe, Alemania

Conferencia; International Conference on Magnetism; 2009

International Union for Pure and Applied Physics (IUPAP)

We present in this work a neutron diffraction study of the system Y(Ba,X)Co2O5+¦Ä for¦Ä ¡Ö 0.5, which focusses on the effects of the substitution of Ba with X=Ca,Sr. Through thiscation substitution, we could stabilize different crystal and magnetic structures, mappingthe complex phase diagram of this layered cobaltite using thermodiffraction techniques. Byadding Ca at the Ba site, the low temperature antiferromagnetic (AFM) long¨Crange orderof the parent compound YBaCo2O5.5 is destroyed, and a ferrimagnetic phase with spinstate order can be stabilized. For the parent compound a two¨Cphase scenario is proposed.In contrast with the effect of substituting Ba sites with Ca, Sr favors a tetragonal symmetryand reinforces the two-phase scenario. We have found that small amounts of Sr quicklydestabilize the ferrimagnetic spin-state ordered phase, leading to a phase separation intodifferent magnetic arrangements at low temperature.