Abstract
This work investigates the electronic structure of CoF3 by optical absorption and its relationship with the ground-state spin and the Jahn–Teller (JT) effect exhibited by Co3+(d6) in octahedral coordination (CoF6)3−. The results are compared with other Co3+ fluorides and oxides, where Co3+ is high spin (HS) and low spin (LS), respectively. In CoF3 we detect an absorption band with a doublet structure at 1.89 eV (657 nm) and 1.45 eV (855 nm) at 2.5 GPa, which is associated with the T ⊗ e JT effect on the 5T2 HS ground state. Absorption measurements under pressure have been carried out around the HS–LS (5T2 ↔1A1) spin crossover transition in the 0–20 GPa range. We show that the JT effect is stable in a wide pressure range. No sign of intermediate spin (3T1, 2 states) is observed in the explored pressure range.
Acknowledgements
Financial support from the Spanish MEC (Project No MAT2005-00099) and MALTA INGENIO-CONSOLIDER 2010 (Ref. CDS2007-0045) are acknowledged. MNSO thanks the Spanish MEC for a FPU grant (Ref. AP-2004-5954).