Different Look at the Spin State ofCo3+Ions in aCoO5Pyramidal Coordination

Abstract

Using soft-x-ray absorption spectroscopy at the Co L(2,3) and O K edges, we demonstrate that the Co3+ ions with the CoO5 pyramidal coordination in the layered Sr2CoO3Cl compound are unambiguously in the high spin state. Our result questions the reliability of the spin state assignments made so far for the recently synthesized layered cobalt perovskites and calls for a reexamination of the modeling for the complex and fascinating properties of these new materials.

Long-range ferromagnetic order inLaCoO3−δepitaxial films due to the interplay of epitaxial strain and oxygen vacancy ordering

“…The reference spectrum from CoO represents HS Co 2+ in an octahedral coordination, 25 while EuCoO 3 spectrum represents LS Co 3+ in an octahedral coordination. 26 The only available reference spectra for purely HS Co 3+ is that of Sr 2 CoO 3 Cl where HS Co 3+ is in a pyramidal coordination.…”

“…26 While temperature dependent spectra of octahedrally coordinated Co in a mixture of high and low spin configurations do exist for bulk LCO (and show similar line shape trends with temperature and spin state) 27 we chose these extreme cases (100% HS and 100% LS at 300K) for our comparisons. But even in these references the differences are subtle and it is difficult to make strong statements concerning the quantity of HS Co 3+ in our samples.…”

Valence, spin, and orbital state of Co ions in one-dimensionalCa3Co2O6: An x-ray absorption and magnetic circular dichroism study

“…8 The Co-L 2,3 XAS spectra of Ca 3 Co 2 O 6 and of CoO and EuCoO 3 (Ref. 20) as references were recorded at the Dragon beamline of the National Synchrotron Radiation Research Center (NSRRC) in Taiwan with an energy resolution of 0.3 eV. The first sharp peak at 777 eV of photon energy at the Co-L 3 edge of CoO was used for energy calibration, which enabled us to achieve better than 0.05 eV accuracy in the relative energy alignment.…”

Ferrimagnetism in PrCoO3epitaxial films

“…XMCD signals are found at both the Co L 2,3 (2p to 3d ) and Pr M 4,5 (3d to 4f ) absorption edges, thus indicating that the ferromagnetism comes from both Co and Pr. The spectra from our films are compared to spectral results in literature [18][19][20][21] to provide insight into the films' spin state, valence, and site symmetry.…”