Enhancing spin state phase separation by strontium addition in the Y(Ba1−xSrx)Co2O5.5 layered cobaltite

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

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Año: 2009 vol. 21 p. 326002 - 326008

0953-8984

In this paper we present a neutron diffraction study of the effects of replacing Ba with smallerSr cations in the layered cobaltite YBaCo2O5+¦Ä for ¦Ä ¡Ö 0.5. Neutron thermodiffractograms arereported in the temperature range 20 K < T < 300 K, as well as high-resolution neutrondiffraction experiments at selected temperatures. The systematic refinement of the series ofsamples with Sr substituting at the Ba site permits the understanding of the complex magneticbehaviour of this system, and reinforces a two-phase scenario for the parent compound. Wehave found that Sr addition destabilizes the ferrimagnetic spin state ordered phase, as well asthe ¡®122¡¯ order characteristic of cobaltites with ¦Ä = 0.5, favouring instead a tetragonal and lessordered structure.