The doping series Eu1-xCaxCoO3-δ provides a rather peculiar way to study the spin-state transitions in cobalt-based complex oxides since partial substitution of Eu3+ ions by Ca2+ ions does not increase the mean valence of cobalt but is accompanied by appearance of oxygen vacancies in the ratio δ∼ x/2. In the parent compound EuCoO3, the low spin (LS)–intermediate spin (IS) or high spin (HS) transition takes place at temperatures so high that the chemical decomposition prevents its direct observation. The substitution of Eu3+ by Ca2+ shifts the spin state transition to lower temperatures and the associated energy gap Δ in octahedrally-coordinated Co3+ ions changes from 1940 K in EuCoO3 to 1540 K in Eu0.9Ca0.1CoO2.95 and 1050 K in Eu0.8Ca0.2CoO2.9. Besides, each O2- vacancy reduces the local coordination of two neighboring Co3+ ions from octahedral to pyramidal thereby locally creating magnetically active sites which couple to dimers. These dimers form another gapped magnetic system with a very different energy scale, Ddim∼3Ddim∼3 K, on the background of the intrinsically non-magnetic lattice of octahedrally-coordinated low-spin Co3+ ions.
Spin-state transition, magnetism and local crystal structure in Eu 1-xCaxCoO3-δ
LOMACHENKO, KIRILL;
2013-01-01
Abstract
The doping series Eu1-xCaxCoO3-δ provides a rather peculiar way to study the spin-state transitions in cobalt-based complex oxides since partial substitution of Eu3+ ions by Ca2+ ions does not increase the mean valence of cobalt but is accompanied by appearance of oxygen vacancies in the ratio δ∼ x/2. In the parent compound EuCoO3, the low spin (LS)–intermediate spin (IS) or high spin (HS) transition takes place at temperatures so high that the chemical decomposition prevents its direct observation. The substitution of Eu3+ by Ca2+ shifts the spin state transition to lower temperatures and the associated energy gap Δ in octahedrally-coordinated Co3+ ions changes from 1940 K in EuCoO3 to 1540 K in Eu0.9Ca0.1CoO2.95 and 1050 K in Eu0.8Ca0.2CoO2.9. Besides, each O2- vacancy reduces the local coordination of two neighboring Co3+ ions from octahedral to pyramidal thereby locally creating magnetically active sites which couple to dimers. These dimers form another gapped magnetic system with a very different energy scale, Ddim∼3Ddim∼3 K, on the background of the intrinsically non-magnetic lattice of octahedrally-coordinated low-spin Co3+ ions.File | Dimensione | Formato | |
---|---|---|---|
Vasiliev JPSJ13 Cobaltites.pdf
Accesso riservato
Descrizione: Articolo principale
Tipo di file:
PDF EDITORIALE
Dimensione
2.6 MB
Formato
Adobe PDF
|
2.6 MB | Adobe PDF | Visualizza/Apri Richiedi una copia |
Vasiliev JPSJ13.pdf
Open Access dal 03/05/2016
Descrizione: Postprint Open Access
Tipo di file:
POSTPRINT (VERSIONE FINALE DELL’AUTORE)
Dimensione
1.58 MB
Formato
Adobe PDF
|
1.58 MB | Adobe PDF | Visualizza/Apri |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.