Structural Phase Transition and Dielectric Properties of ZnCr 2 O 4

Kagomiya, Isao; Sawa, Hiroshi; Siratori, Kiiti; Kohn, Kay; Toki, M.; Hata, Yoshiaki; Kita, Eiji

doi:10.1080/00150190211050

Cited by 25 publications

(25 citation statements)

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“…A x-ray powder-diffraction study was also performed for ZnCr 2 O 4 by Kagomiya et al 35 and a Rietveld refinement below T N was performed for the orthorhombic Fddd symmetry ͑70͒. For this structure the factor-group analysis gives ⌫ = 7B 1u + 7B 2u + 7B 3u ͑IR active͒ + 3A g + 4B 1g + 4B 2g + 4B 3g ͑Raman active͒ + 6A u ͑silent͒.…”

Section: Infrared Spectroscopymentioning

confidence: 99%

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
71
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.

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Section: Infrared Spectroscopymentioning

confidence: 99%

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
71
3
27
0
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“…[1][2][3] At the same time, it was disclosed that a magnetic field of several tens of kOe, applied along the h111i axis during the cooling of the specimen through T N , affects the intensities of the magnetic diffraction peaks in the low-temperature phase. 4) Thus, the magnetic symmetry of the low-temperature phase of ZnCr 2 O 4 is monoclinic or lower, with a possible 2-fold axis along one of the h110i axes and a possible mirror plane perpendicular to the 2-fold axis.…”

Section: Introductionmentioning

confidence: 99%

Symmetry Breaking in a Frustrated Heisenberg Spin System, ZnCr₂O₄: I. Magnetic Measurements

et al. 2006

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Magnetization was measured for a ZnCr 2 O 4 single crystal as a function of field direction, in a magnetic field range of 0.5 -50 kOe, mainly at 5 K. To examine the effect of magnetic domain distribution, the crystal was cooled through T N , 12.2 K, with or without pressure along the [001] axis and a magnetic field of 50 kOe along the [1 "1 11] or of 60 kOe along the [0 "1 11] axis. No spontaneous magnetization was detected within the accuracy of the experiment. Above 3 kOe, the anisotropy of magnetic susceptibility decreases with increasing magnetic field, to approximately two or three orders of magnitude smaller at 30 kOe. This finding indicates that the ground state lies near the magnetically isotropic (symmetric) state but is slightly distorted. The energy difference between the symmetric state and the ground state was estimated to be on the order of 10 À2 J/g or 10 À3 cm À1 /Cr ion, by magnetization curves. It was suggested that the magnetic symmetry of the ground state is lower than monoclinic.

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“…Arguments for both tetragonal and orthorhombic symmetry for the crystal structure have been advanced. 132 Finally, this material is extremely sensitive to positional disorder; only 3% substitution of Ga 3+ for Cr 3+ and 5% Cd 2+ for Zn 2+ can induce a spin glass ground state. valence.…”

Section: 128mentioning

confidence: 99%

Magnetic Oxides

Greedan

2005

Encyclopedia of Inorganic Chemistry

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An attempt has been made to survey the research activity in selected aspects of the field of magnetic oxides for the period ∼1993 to the present. Emphasis has been placed on oxides with the perovskite and related structures such as the Ruddlesden–Popper phases, A‐site and B‐site ordered perovskites, pillared perovskites, and materials with structures related to the hexagonal perovskites. As well, the field of geometrically frustrated magnetic materials is reviewed with emphasis on materials with the pyrochlore, spinel, and related structures. Phenomena exhibited by such compounds include colossal magneto‐resistance, charge and orbital ordering, half‐metallic ferromagnetism, low‐dimensional magnetism, spin glass, spin liquid, and spin ice ordering, among others.

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Structural Phase Transition and Dielectric Properties of ZnCr 2 O 4

Cited by 25 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
71
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
71
3
27
0
View full text Add to dashboard Cite

Symmetry Breaking in a Frustrated Heisenberg Spin System, ZnCr₂O₄: I. Magnetic Measurements

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Structural Phase Transition and Dielectric Properties of ZnCr 2 O 4

Cited by 25 publications

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Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2Kant1, Deisenhofer2, Rudolf3 et al. 2009Phys. Rev. B713270View full textAdd to dashboardCite

Optical phonons, spin correlations, and spin-phonon coupling in the frustrated pyrochlore magnetsCdCr2O4andZnCr2Kant1, Deisenhofer2, Rudolf3 et al. 2009Phys. Rev. B713270View full textAdd to dashboardCite

Symmetry Breaking in a Frustrated Heisenberg Spin System, ZnCr2O4: I. Magnetic Measurements

Magnetic Oxides

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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
71
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
71
3
27
0
View full text Add to dashboard Cite

Symmetry Breaking in a Frustrated Heisenberg Spin System, ZnCr₂O₄: I. Magnetic Measurements