We show by electron spin resonance (ESR) and Raman spectroscopies that the crystal phase transition of the lead-free double-perovskite Cs2AgBiBr6 has a profound symmetry-breaking effect on the high spin states of, for example, a transition-metal ion Fe3+ and the vibrational modes. It lifts their degeneracy when the crystal undergoes the cubic-tetragonal phase transition, splitting the six-fold degenerate S = 5/2 state of Fe3+ to three Kramer doublets and the enharmonic breathing mode Tg of the MBr6 octahedra (M = Ag, Bi, Fe) into Eg + Ag. The magnitudes of both spin and Raman line splitting are shown to directly correlate with the strength of the tetragonal strain field. This work, in turn, demonstrates the power of the ESR and Raman spectroscopies in probing structural phase transitions and in providing in-depth information on the interplay between the structural, spin, and vibrational properties of lead-free double perovskites, a newly emerging and promising class of materials for low-cost and high-efficiency photovoltaics and optoelectronics.

Puttisong, Y., Moro, F., Chen, S., Hojer, P., Ning, W., Gao, F., et al. (2020). Effect of Crystal Symmetry on the Spin States of Fe3+and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br6. THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 11(12), 4873-4878 [10.1021/acs.jpclett.0c01543].

Effect of Crystal Symmetry on the Spin States of Fe3+and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br6

Moro F.
Co-primo
;
2020

Abstract

We show by electron spin resonance (ESR) and Raman spectroscopies that the crystal phase transition of the lead-free double-perovskite Cs2AgBiBr6 has a profound symmetry-breaking effect on the high spin states of, for example, a transition-metal ion Fe3+ and the vibrational modes. It lifts their degeneracy when the crystal undergoes the cubic-tetragonal phase transition, splitting the six-fold degenerate S = 5/2 state of Fe3+ to three Kramer doublets and the enharmonic breathing mode Tg of the MBr6 octahedra (M = Ag, Bi, Fe) into Eg + Ag. The magnitudes of both spin and Raman line splitting are shown to directly correlate with the strength of the tetragonal strain field. This work, in turn, demonstrates the power of the ESR and Raman spectroscopies in probing structural phase transitions and in providing in-depth information on the interplay between the structural, spin, and vibrational properties of lead-free double perovskites, a newly emerging and promising class of materials for low-cost and high-efficiency photovoltaics and optoelectronics.
Articolo in rivista - Articolo scientifico
iron, perovskites, electron paramagnetic resonance
English
3-giu-2020
2020
11
12
4873
4878
reserved
Puttisong, Y., Moro, F., Chen, S., Hojer, P., Ning, W., Gao, F., et al. (2020). Effect of Crystal Symmetry on the Spin States of Fe3+and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br6. THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 11(12), 4873-4878 [10.1021/acs.jpclett.0c01543].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/289265
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