Low-temperature infrared studies

Heyns, A.M.; Schutte, C. J. H.

doi:10.1016/0022-2860(71)80011-x

Cited by 20 publications

(12 citation statements)

References 19 publications

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“…We emphasize that the 2 H-and 1 H-resonance lines measured with NMR on deuterated and protonated powder samples are split at T 150 K [15]. Further evidence for a structural transition in NH 4 CuCl 3 is reported in an early IR absorption study [16] as well as in ultrasonic experiments with anomalies in the temperature dependence of the elastic constants occurring at T 70 K [17]. Recent NMR results additionally show a splitting of the 15 N-resonance line around this temperature [18].…”

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confidence: 85%

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3
Rüegg
¹
,
Oettli
²
,
Schefer
³

et al. 2004
Phys. Rev. Lett.
36
2
13
0
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Elastic and inelastic neutron scattering experiments have been performed on the dimer spin system NH4CuCl3, which shows plateaus in the magnetization curve at m=1/4 and m=3/4 of the saturation value. Two structural phase transitions at T1 approximately 156 K and at T(2)=70 K lead to a doubling of the crystallographic unit cell along the b direction and as a consequence a segregation into different dimer subsystems. Long-range magnetic ordering is reported below T(N)=1.3 K. The magnetic field dependence of the excitation spectrum identifies successive quantum phase transitions of the dimer subsystems as the driving mechanism for the unconventional magnetization process in agreement with a recent theoretical model.

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mentioning

confidence: 85%

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3
Rüegg
¹
,
Oettli
²
,
Schefer
³

et al. 2004
Phys. Rev. Lett.
36
2
13
0
View full text Add to dashboard Cite

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“…6(a), Tables 6, S5). The Cu-O ax stretching modes found for the hexaaquacopper(II) complex in Cu ClO 4 2 Ð 6H 2 O (1), at 333 cm 1 (Raman) and at 382 cm 1 (IR), are close to the corresponding Raman and IR bands for LiCuCl 3 Ð 2H 2 O (6) at 335 and 378 cm 1 , and are assigned as the symmetric, 2 A 1g , and asymmetric, 6 A 2u , Cu-O ax stretchings, respectively (Tables 4, S5, S10). For the equatorial plane of a dimeric Cu 2 Cl 6 complex with D 2h point group symmetry, the symmetric Cu-Cl term stretching for the terminal chlorides, 1 A g , at 272 cm 1 and the symmetric Cu-Cl br stretching for the bridging chlorides, 2 A g , at 235 cm 1 give rise to prominent Raman bands.…”

Section: Aquachlorocuprates(ii)mentioning

confidence: 99%

Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr₃

Stepakova

Skripkin

Chernykh

et al. 2007

J Raman Spectroscopy

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Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching Cu II -X modes in the equatorial plane, were found in the ranges 247-288 cm −1 for X = Cl, and 173-189 cm −1 for X = Br, while the low-wavenumber stretching modes for the weaker axial Cu-X interactions varied considerably. The tetrahedral coordination for Cs 2 CuCl 4 and Cs 2 CuBr 4 leads to somewhat lower Cu-X symmetric stretching wavenumbers, 295 and 173 cm −1 , respectively. The assignments of the copper-ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged Cu-X stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn-Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer-sphere cations. Force constant ratios for terminal and bridging metal-halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M 2 X 6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr 3 (K 2 Cu 2 Br 6 ), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu 2 Br 6 ] 2− complexes held together by weak axial Cu-Br interactions.

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“…It has been reported that NH 4 CuCl 3 undergoes a structural phase transition at T s ∼ 70 K. 16,17) The locking of the rotational motion of NH 4+ ions seems to cause the structural phase transition. It is likely that the unit cell is enlarged below T s , so that the exchange interactions are modulated.…”

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Magnetization Plateaus in NH₄CuCl₃

et al. 1998

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The magnetic susceptibility and high-field magnetization process of NH 4 CuCl 3 with double chains of CuCl 3 have been measured using single crystals. No anomaly indicative of the threedimensional ordering is observed in susceptibility data above 1.7 K. It is found, by magnetization measurement down to 0.5 K, that in contrast to KCuCl 3 and TlCuCl 3 , NH 4 CuCl 3 has a gapless magnetic ground state at zero field. It is observed that the magnetization curve has two plateaus at one-quarter and three-quarters of the saturation magnetization, irrespective of the external field direction. The origin of the plateaus is attributed not to the magnetic anisotropy, but to the quantum effect. The relation between the plateaus and the period of the spin state is discussed in terms of a recent theory presented by Oshikawa et al. [Phys. Rev. Lett. 78 (1997) 1984.KEYWORDS: NH 4 CuCl 3 , double chain, high field, magnetization process, magnetization plateausThe magnetization processes of low-dimensional quantum spin systems with spatial structures such as spin ladders and exchange-alternating chains, are new problems in magnetism. In particular, magnetization plateaus are of great interest, because the magnetization is quantized at the plateaus. In a spin-1/2 Heisenberg chain with ferromagnetic (J F )-ferromagnetic (J F )-antiferromagnetic (J AF ) interactions, the magnetization curve has a plateau at 1/3 of the saturation magnetization M s , when J F /J AF < 5 ∼ 6.1, 2) For a spin-1/2 antiferromagnetic alternating Heisenberg chain with the next-nearestneighbor interaction, a plateau can appear at (1/2)M s in an appropriate parameter region. 3,4) In this case the next-nearest-neighbor interaction is essential for the existence of the plateau. The period of the spin state at the plateau is twice as large as the period of the Hamiltonian.4) Thus the plateau is caused by the quantum manybody effect. For a spin-1 antiferromagnetic Heisenberg chain, a plateau exists at (1/2)M s as long as the exchange interaction alternates.5, 6) The 1/2-plateau has been observed experimentally in the nickel compound8) investigated general Heisenberg chains in a magnetic field. They showed that the magnetization can have plateaus, and that it is quantized at the plateaus aswhere n is the period of the spin state, S the magnitude of spin and m the magnetization per site in the unit of gμ B . All of the above-mentioned plateaus satisfy this quantization condition. * Author to whom correspondence should be addressed. E-mail: tanaka@lee.cme.phys.titech.ac.jp 1548In this letter we report the magnetization plateaus observed in NH 4 CuCl 3 . At room temperature, NH 4 CuCl 3 is isostructural with KCuCl 3 which belongs to the monoclinic space group P 2 1 /c. 9, 10) The crystal structure is composed of double chains of edge-sharing CuCl 6 octahedra along the a-axis. The double chains are located at the corners and center of the unit cell in the bc-plane, and are separated by NH 4+ ions. There are three kinds of nearest-neighbor-interactions, J 1 , J 2 and J 3...

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Low-temperature infrared studies

Cited by 20 publications

References 19 publications

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3
Rüegg
¹
,
Oettli
²
,
Schefer
³

et al. 2004
Phys. Rev. Lett.
36
2
13
0
View full text Add to dashboard Cite

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3
Rüegg
¹
,
Oettli
²
,
Schefer
³

et al. 2004
Phys. Rev. Lett.
36
2
13
0
View full text Add to dashboard Cite

Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr₃

Magnetization Plateaus in NH₄CuCl₃

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Low-temperature infrared studies

Cited by 20 publications

References 19 publications

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3Rüegg1, Oettli2, Schefer3 et al. 2004Phys. Rev. Lett.362130View full textAdd to dashboardCite

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3Rüegg1, Oettli2, Schefer3 et al. 2004Phys. Rev. Lett.362130View full textAdd to dashboardCite

Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr3

Magnetization Plateaus in NH 4CuCl 3

Contact Info

Product

Resources

About

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3
Rüegg
¹
,
Oettli
²
,
Schefer
³

et al. 2004
Phys. Rev. Lett.
36
2
13
0
View full text Add to dashboard Cite

Neutron Scattering Study of the Field-Dependent Ground State and the Spin Dynamics in Spin-One-HalfNH4CuCl3
Rüegg
¹
,
Oettli
²
,
Schefer
³

et al. 2004
Phys. Rev. Lett.
36
2
13
0
View full text Add to dashboard Cite

Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr₃

Magnetization Plateaus in NH₄CuCl₃