Lattice Vibration Spectra

Zwinscher, J.; Lutz, H. D.

doi:10.1006/jssc.1995.1308

Cited by 28 publications

(17 citation statements)

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“…Explicit snapshots of the ion displacements for all phonon modes can be found in the work of Zwinscher and Lutz. 39 This strongly suggests that below T N inversion symmetry is lost in agreement with the theoretical predictions by Chern and co-workers, who stated that the spiral magnetic ground state could be enabled by a chiral nature of the underlying lattice and proposed I4 1 22 for the space-group symmetry. 14,15 From the infrared and Raman data we cannot identify a strong softening of an optical phonon mode in CdCr 2 O 4 .…”

Section: Raman Scatteringsupporting

confidence: 69%

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2
Kant
¹
,
Deisenhofer
²
,
Rudolf
³

et al. 2009
Phys. Rev. B
69
3
27
0
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We report on infrared, Raman, magnetic susceptibility, and specific-heat measurements on CdCr 2 O 4 and ZnCr 2 O 4 single crystals. We estimate the nearest-neighbor and next-nearest-neighbor exchange constants from the magnetic susceptibility and extract the spin-spin correlation functions obtained from the magnetic susceptibility and the magnetic contribution to the specific heat. By comparing with the frequency shift of the infrared optical phonons above T N , we derive estimates for the spin-phonon coupling constants in these systems. The observation of phonon modes which are both Raman and infrared active suggest the loss of inversion symmetry below the Néel temperature in CdCr 2 O 4 in agreement with theoretical predictions by Chern et al. ͓Phys. Rev. B 74, 060405͑R͒ ͑2006͔͒. In ZnCr 2 O 4 several new modes appear below T N but no phonon modes could be detected which are both Raman and infrared active.

show abstract

Section: Raman Scatteringsupporting

confidence: 69%

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2
Kant
¹
,
Deisenhofer
²
,
Rudolf
³

et al. 2009
Phys. Rev. B
69
3
27
0
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“…2). At ambient conditions, we could observe all of the expected Fd3 m Raman-active modes 56,57 . Upon increasing pressure, the Fd3 m Raman features could be followed up to 10 GPa.…”

Section: Resultsmentioning

confidence: 90%

Pressure-induced phase transitions in the CdCr2Se4 spinel

et al. 2016

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We have conducted high-pressure x-ray diffraction and Raman spectroscopic studies on the CdCr 2 Se 4 spinel at room temperature up to 42 GPa. We have resolved three structural transitions up to 42 GPa, i.e. the starting Fd3 m phase transforms at ~11 GPa into a tetragonal I4 1 /amd structure, an orthorhombic distortion was observed at ~15 GPa, whereas structural disorder initiates beyond 25 GPa. Our ab initio DFT studies successfully reproduced the observed crystalline-to-crystalline structural transitions. In addition, our calculations propose an anti-ferromagnetic ordering as a potential magnetic ground state for the high-pressure tetragonal and orthorhombic modifications, as compared to the starting ferromagnetic phase. Furthermore, the computational results indicate that all phases remain insulating in their stability pressure range, with a direct-to-indirect band gap transition for the Fd3 m phase taking place at 5 GPa.We attempted also to offer an explanation behind the peculiar first-order character of the Fd3 m (cubic)→I4 1 /amd (tetragonal) transition observed for several relevant Cr-spinels, i.e. the sizeable volume change at the transition point, which is not expected from space group symmetry considerations. We detected a clear correlation between the cubic-tetragonal transition pressures and the next-nearest-neighbor magnetic exchange interactions for the Crbearing sulphide and selenide members, a strong indication that the cubic-tetragonal transitions in these systems are principally governed by magnetic effects.

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“…43,44 In infrared experiments the oscillator strength is directly related to the ionicity of a bond. 47 The more ionic the character of the bond is, the stronger will be the vibrational mode belonging to that bond.…”

Section: Discussionmentioning

confidence: 99%

Evolution of the optical properties of chromium spinels CdCr2O4, HgCr2S
Rabia
¹
,
Baldassarre
²
,
Tsurkan
³

et al. 2014
Phys. Rev. B
10
2
4
0
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We report pressure-dependent reflection and transmission measurements on ZnCr2Se4, HgCr2S4, and CdCr2O4 single crystals at room temperature over a broad spectral range 200-24000 cm −1 . The pressure dependence of the phonon modes and the high-frequency electronic excitations indicates that all three compounds undergo a pressure-induced structural phase transition with the critical pressure 15 GPa, 12 GPa, and 10 GPa for CdCr2O4, HgCr2S4, and ZnCr2Se4, respectively. The eigenfrequencies of the electronic transitions are very close to the expected values for chromium crystal-field transitions. In the case of the chalcogenides pressure induces a red shift of the electronic excitation which indicates a strong hybridization of the Cr d-bands with the chalcogenide bands.

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Lattice Vibration Spectra

Cited by 28 publications

References 0 publications

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2
Kant
¹
,
Deisenhofer
²
,
Rudolf
³

et al. 2009
Phys. Rev. B
69
3
27
0
View full text Add to dashboard Cite

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2
Kant
¹
,
Deisenhofer
²
,
Rudolf
³

et al. 2009
Phys. Rev. B
69
3
27
0
View full text Add to dashboard Cite

Pressure-induced phase transitions in the CdCr2Se4 spinel

Evolution of the optical properties of chromium spinels CdCr2O4, HgCr2S
Rabia
¹
,
Baldassarre
²
,
Tsurkan
³

et al. 2014
Phys. Rev. B
10
2
4
0
View full text Add to dashboard Cite

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Lattice Vibration Spectra

Cited by 28 publications

References 0 publications

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2Kant1, Deisenhofer2, Rudolf3 et al. 2009Phys. Rev. B693270View full textAdd to dashboardCite

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2Kant1, Deisenhofer2, Rudolf3 et al. 2009Phys. Rev. B693270View full textAdd to dashboardCite

Pressure-induced phase transitions in the CdCr2Se4 spinel

Evolution of the optical properties of chromium spinels CdCr2O4, HgCr2SRabia1, Baldassarre2, Tsurkan3 et al. 2014Phys. Rev. B10240View full textAdd to dashboardCite

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Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2
Kant
¹
,
Deisenhofer
²
,
Rudolf
³

et al. 2009
Phys. Rev. B
69
3
27
0
View full text Add to dashboard Cite

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2
Kant
¹
,
Deisenhofer
²
,
Rudolf
³

et al. 2009
Phys. Rev. B
69
3
27
0
View full text Add to dashboard Cite

Evolution of the optical properties of chromium spinels CdCr2O4, HgCr2S
Rabia
¹
,
Baldassarre
²
,
Tsurkan
³

et al. 2014
Phys. Rev. B
10
2
4
0
View full text Add to dashboard Cite