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. 2019 Mar 1;9(1):3223.
doi: 10.1038/s41598-019-39031-6.

Spin-charge-lattice coupling in YBaCuFeO5: Optical properties and first-principles calculations

H W Chen  1 , Y-W Chen  2 , J-L Kuo  2 , Y C Lai  3   4 , F C Chou  3 , C H Du  4 , H L Liu  5
Affiliations

Spin-charge-lattice coupling in YBaCuFeO5: Optical properties and first-principles calculations

H W Chen et al. Sci Rep. .

Abstract

We combined spectroscopic ellipsometry, Raman scattering spectroscopy, and first-principles calculations to explore the optical properties of YBaCuFeO5 single crystals. Measuring the optical absorption spectrum of YBaCuFeO5 at room temperature revealed a direct optical band gap at approximately 1.41 eV and five bands near 1.69, 2.47, 3.16, 4.26, and 5.54 eV. Based on first-principles calculations, the observed optical excitations were appropriately assigned. Analysis of the temperature dependence of the band gap indicated anomalies in antiferromagnetic phase transition at 455 and 175 K. Additionally, a hardening in the frequency of the Eg phonon mode was observed at 175 K. The value of the spin-phonon coupling constant was 15.7 mRy/Å2. These results suggest a complex nature of spin-charge-lattice interactions in YBaCuFeO5.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
X-ray powder diffraction patterns of YBaCuFeO5 at 300 and 90 K.
Figure 2
Figure 2
(a) Dielectric function for YBaCuFeO5 at room temperature. (b) Optical absorption coefficient of YBaCuFeO5 at room temperature. The dashed lines indicate the best fit from the Lorentzian model. The inset illustrates the direct band gap analysis of YBaCuFeO5.
Figure 3
Figure 3
Temperature dependence of the optical absorption spectra of YBaCuFeO5.
Figure 4
Figure 4
The energy band gap as a function of temperature for YBaCuFeO5. The thin solid line indicates the result of the fitting using the Bose–Einstein model. Vertical dashed lines denote transition temperatures.
Figure 5
Figure 5
(a) Calculated electronic band structure, density of states (DOS), and (b) calculated and experimental optical absorption coefficient of YBaCuFeO5. The inset in (b) depicts the atomic structure of the simulation model with dark cyan, green, blue, brown, and red spheres representing the Y, Ba, Cu, Fe, and O atoms, respectively. The pyramids formed by oxygen atoms embracing Cu and Fe atoms are also highlighted.
Figure 6
Figure 6
(a) Unpolarized Raman scattering spectrum of YBaCuFeO5 at room temperature. The inset illustrates the Raman scattering spectra in parallel and cross scattering geometries. (b) Temperature dependence of unpolarized Raman scattering spectra of YBaCuFeO5. The inset denotes the fitting results of spectra at 300 and 10 K using the Lorentzian and Fano models.
Figure 7
Figure 7
Temperature dependence of the frequency, linewidth, normalized intensity, and asymmetry factors of (a) Eg and (b) A1g phonon modes of YBaCuFeO5. The thin solid lines indicate the results of the fitting from the anharmonic model. Vertical dashed lines denote transition temperatures.
See this image and copyright information in PMC

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