Spin State and Spin-State Transition of Co3+ Ion in BiCoO3

Confusion has arisen about the Co spin-state transition under high pressure for multiferroic BiCoO3. The crystal structure analysis indicates a high-spin (HS) to low-spin (LS) state transition with increasing pressure, while Co K beta X-ray emission spectra present a high-spin to intermediate-spin (IS) state transition. Herein, the spin state of Co3+ in BiCoO3 is investigated utilizing soft X-ray absorption spectroscopy (XAS) at the Co-L-2,L-3 and O-K edges at room temperature under ambient pressure. Furthermore, the spin state transition of Co3+ under high pressure is investigated by Co K beta X-ray emission spectra. A pure HS-Co3+ ground state is found in the BiCoO3 sample prepared from the precursor and oxidizer mixed method-and the existence of a small part of LS-Co3+ in the BiCoO3 sample prepared from the precursor and oxidizer sandwiched method. A complete HS-Co3+ to LS-Co3+ transition is observed under high pressure up to 32.3 GPa. The results clarify the debate on the spin-state transition of BiCoO3 under high pressure and will deepen our understanding of the intrinsic physical properties on it.

Automated summary

This study investigates the spin state transition of Co3+ in BiCoO3 using various techniques, revealing a complete transition from high-spin to low-spin state under high pressure. These findings clarify the debate on the spin-state transition of BiCoO3 and contribute to a deeper understanding of its intrinsic physical properties.