The pressure evolution of the local structure of Fe2O3 hematite has been determined by extended x-ray absorption fine structure up to ∼79 GPa. Below the phase-transition pressure at ∼50 GPa, no increasing of FeO6 octahedra distortion is observed as pressure is applied. Above the phase transition, an abrupt decrease of the nearest-neighbor Fe-O distance is observed concomitantly with a strong reduction in the FeO6 distortion. This information on the local structure, used as a test-bench for the different high-pressure forms proposed in the literature, suggests that the orthorhombic structure with space group Aba2, recently proposed by Bykova [Nat. Commun. 7, 10661 (2016)2041-172310.1038/ncomms10661], is the most probable, but puts into question the presence of the P21/n form in the pressure range 54-67 GPa. Finally, the crossover from Fe high-spin to low-spin states with pressure increase has been monitored from the pre-edge region of the Fe K-edge absorption spectra. Its "simultaneous" comparison with the local structural changes allows us to conclude that it is the electronic transition that drives the structural transition and not vice versa.

Sanson, A., Kantor, I., Cerantola, V., Irifune, T., Carnera, A., Pascarelli, S. (2016). Local structure and spin transition in Fe2O3 hematite at high pressure. PHYSICAL REVIEW. B, 94(1) [10.1103/PhysRevB.94.014112].

Local structure and spin transition in Fe2O3 hematite at high pressure

Cerantola V;
2016

Abstract

The pressure evolution of the local structure of Fe2O3 hematite has been determined by extended x-ray absorption fine structure up to ∼79 GPa. Below the phase-transition pressure at ∼50 GPa, no increasing of FeO6 octahedra distortion is observed as pressure is applied. Above the phase transition, an abrupt decrease of the nearest-neighbor Fe-O distance is observed concomitantly with a strong reduction in the FeO6 distortion. This information on the local structure, used as a test-bench for the different high-pressure forms proposed in the literature, suggests that the orthorhombic structure with space group Aba2, recently proposed by Bykova [Nat. Commun. 7, 10661 (2016)2041-172310.1038/ncomms10661], is the most probable, but puts into question the presence of the P21/n form in the pressure range 54-67 GPa. Finally, the crossover from Fe high-spin to low-spin states with pressure increase has been monitored from the pre-edge region of the Fe K-edge absorption spectra. Its "simultaneous" comparison with the local structural changes allows us to conclude that it is the electronic transition that drives the structural transition and not vice versa.
Articolo in rivista - Articolo scientifico
hematite; spin transition; structural transition; XAS; EXAFS; diamond anvil cell; high pressure
English
Sanson, A., Kantor, I., Cerantola, V., Irifune, T., Carnera, A., Pascarelli, S. (2016). Local structure and spin transition in Fe2O3 hematite at high pressure. PHYSICAL REVIEW. B, 94(1) [10.1103/PhysRevB.94.014112].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/397792
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