Simultaneous first-order valence and oxygen vacancy order/disorder transitions in (Pr0.85Y0.15)0.7Ca0.3CoO3-δ via analytical transmission electron microscopy

Ahmet Gulec, Daniel Phelan, Chris Leighton, Robert F. Klie

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Perovskite cobaltites have been studied for years as some of the few solids to exhibit thermally driven spin-state crossovers. The unanticipated first-order spin and electronic transitions recently discovered in Pr-based cobaltites are notably different from these conventional crossovers, and are understood in terms of a unique valence transition. In essence, the Pr valence is thought to spontaneously shift from 3+ toward 4+ on cooling, driving subsequent transitions in Co valence and electronic/ magnetic properties. Here, we apply temperature-dependent transmission electron microscopy and spectroscopy to study this phenomenon, for the first time with atomic spatial resolution, in the prototypical (Pr0.85Y0.15)0.70 Ca0.30CoO3-δ. In addition to the direct spectroscopic observation of charge transfer between Pr and Co at the 165 K transition (on both the Pr and O edges), we also find a simultaneous order/disorder transition associated with O vacancies. Remarkably, the first-order valence change drives a transition between ordered and random O vacancies, at constant O vacancy density, demonstrating reversible crystallization of such vacancies even at cryogenic temperatures.

Original languageEnglish (US)
Pages (from-to)938-947
Number of pages10
JournalACS Nano
Volume10
Issue number1
DOIs
StatePublished - Jan 26 2016

Fingerprint

Order disorder transitions
Oxygen vacancies
Vacancies
disorders
Transmission electron microscopy
valence
transmission electron microscopy
oxygen
Electron spectroscopy
crossovers
Crystallization
Perovskite
Cryogenics
Charge transfer
Magnetic properties
cryogenic temperature
Cooling
electronics
Temperature
electron spectroscopy

Keywords

  • Electron energy loss spectroscopy
  • Oxygen vacancy ordering
  • Perovskite cobaltites
  • Spin-state transitions
  • Transmission electron microscopy

Cite this

Simultaneous first-order valence and oxygen vacancy order/disorder transitions in (Pr0.85Y0.15)0.7Ca0.3CoO3-δ via analytical transmission electron microscopy. / Gulec, Ahmet; Phelan, Daniel; Leighton, Chris; Klie, Robert F.

In: ACS Nano, Vol. 10, No. 1, 26.01.2016, p. 938-947.

Research output: Contribution to journalArticle

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