INVESTIGADORES
AURELIO Gabriela
artículos
Título:
On the Location of Host Ca Atoms Responsible for Ferrimagnetism in the Layered Cobaltites YBaCo 2 O 5.5
Autor/es:
AURELIO, G.; BARDELLI, F.; JUNQUEIRA PRADO, R.; SÁNCHEZ, R. D.; SALETA, M; GARBARINO, G.
Revista:
CHEMISTRY OF MATERIALS
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2013 vol. 25 p. 3307 - 3314
ISSN:
0897-4756
Resumen:
Recent studies have shown that the addition of Ca as host
ion in the layered compounds RBaCo 2 O 5+δ (with R a rare earth or
yttrium) produces a dramatic effect on their magnetic properties, as well
as on their Seebeck coefficient and resistivity. Studies performed so far
have opened up the possibility that the substitution site for Ca atoms
might not be obvious, having been reported at the Y site, at the Ba site, or
regarded as not decisive to the ferromagnetism enhancement. In this
work, we present a comparative study of Ca-doped cobaltite samples
synthesized with two different nominal substitution sites, namely, Ca
replacing Ba, and Ca replacing Y. X-ray absorption spectroscopy
performed at the Ca, Ba, and Co edges to study the local environment
around these elements allowed to unequivocally determine that the
substitutional site of Ca is the Y site. This important result helps to clarify
the mixed valence state of cobalt as Co 3+ and Co 4+ , which would be responsible for the ferromagnetic interactions, and explains
the antiferromagnetic to ferrimagnetic switch occurring already at 10% Ca doping level.