A Complete
High-to-Low spin state Transition of Trivalent
Cobalt Ion in Octahedral Symmetry in SrCo<sub>0.5</sub>Ru<sub>0.5</sub>O<sub>3‑δ</sub>
Jin-Ming Chen
Yi-Ying Chin
Martin Valldor
Zhiwei Hu
Jenn-Min Lee
Shu-Chih Haw
Nozomu Hiraoka
Hirofumi Ishii
Chih-Wen Pao
Ku-Ding Tsuei
Jyh-Fu Lee
Hong-Ji Lin
Ling-Yun Jang
Arata Tanaka
Chien-Te Chen
Liu Hao Tjeng
10.1021/ja4114006.s001
https://acs.figshare.com/articles/journal_contribution/A_Complete_High_to_Low_spin_state_Transition_of_Trivalent_Cobalt_Ion_in_Octahedral_Symmetry_in_SrCo_sub_0_5_sub_Ru_sub_0_5_sub_O_sub_3_sub_/2328280
The complex metal oxide SrCo<sub>0.5</sub>Ru<sub>0.5</sub>O<sub>3‑δ</sub> possesses a
slightly distorted perovskite
crystal structure. Its insulating nature infers a well-defined charge
distribution, and the six-fold coordinated transition metals have
the oxidation states +5 for ruthenium and +3 for cobalt as observed
by X-ray spectroscopy. We have discovered that Co<sup>3+</sup> ion
is purely high-spin at room temperature, which is unique for a Co<sup>3+</sup> in an octahedral oxygen surrounding. We attribute this to
the crystal field interaction being weaker than the Hund’s-rule
exchange due to a relatively large mean Co–O distances of 1.98(2)
Å, as obtained by EXAFS and X-ray diffraction experiments. A
gradual high-to-low spin state transition is completed by applying
high hydrostatic pressure of up to 40 GPa. Across this spin state
transition, the Co Kβ emission spectra can be fully explained
by a weighted sum of the high-spin and low-spin spectra. Thereby is
the much debated intermediate spin state of Co<sup>3+</sup> absent
in this material. These results allow us to draw an energy diagram
depicting relative stabilities of the high-, intermediate-, and low-spin
states as functions of the metal–oxygen bond length for a Co<sup>3+</sup> ion in an octahedral coordination.
2014-01-29 00:00:00
EXAFS
metal oxide SrCo 0.5Ru
Trivalent Cobalt Ion
Co K β emission spectra
crystal field interaction
state transition
perovskite crystal structure