Zur Kristallstruktur von CuGeO3

Völlenkle, H.; Wittmann, A.; Nowotny, H.

doi:10.1007/bf00909002

Cited by 195 publications

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“…The crystal structure is orthorhombic with a ¼ 4:81 Å , b ¼ 8:47 Å , and c ¼ 2:94 Å . 10) In this material, spins of Cu 2þ ions form S ¼ 1=2 antiferromagnetic (AF) chains along c. The material undergoes a spin-Peierls transition below T sP ¼ 14 K.…”

Section: Lettersmentioning

confidence: 99%

First Demonstration of Novel Method for Inelastic Neutron Scattering Measurement Utilizing Multiple Incident Energies

et al. 2009

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We succeeded in experimentally demonstrating that a series of two-dimensional maps of a dynamical structure factor in momentum-energy space with multiple incident energies can be simultaneously obtained by one measurement. This method reduces the dead time of time-of-flight measurement, and thus, it markedly increases the measurement efficiency. Our achievement realized using the Fermi chopper spectrometer 4SEASONS in J-PARC is expected to open up new possibilities of inelastic neutron scattering measurements.KEYWORDS: pulsed neutron source, Fermi chopper spectrometer, inelastic neutron scattering, multi-E i measurement, J-PARC DOI: 10.1143/JPSJ.78.093002A ''Fermi chopper'' spectrometer is a typical instrument for inelastic neutron scattering (INS) measurement at a pulsed neutron source. The Fermi chopper is used for monochromating the incident neutron beam. Inelastic scattering from a sample is measured by a time-of-flight (TOF) technique over a neutron source period. The accumulated TOF data can be converted to a dynamical structure factor. In fact, the INS measurements conducted using Fermi chopper spectrometers have revealed various mysteries of materials science, and thus, a Fermi chopper spectrometer should remain to be a flagship instrument in new-generation pulsed neutron sources such as the Japan Proton Accelerator Research Complex (J-PARC), which is one of the world's highest intensity pulsed neutron sources.A conventional Fermi chopper has a set of curved slits. The curvature is adjusted to the passage of neutrons with a selected velocity, which means that neutron transmission is optimized for a specific single incident energy (E i ). From another point of view, the curved slits would bring about the inefficiency of an INS measurement. Chopper rotation frequency (100 -600 Hz) is typically much higher than the frequency of the pulsed source (25 Hz in J-PARC), and the utilized TOF region of INS measurement with single E i is approximately less than 10% of the source period (40 ms in J-PARC). To reduce the dead time of TOF measurement, we have proposed the method of utilizing multiple E i beams. 1,2)We apply a set of straight and wide slits to a Fermi chopper, and consequently, a high transmission of neutrons can be achieved over a wide E i range, though the energy resolution is relaxed. Thus, this type of Fermi chopper can select multiple E i beams within the source period, and the simultaneous INS measurements with multiple E i 's can be realized. We refer to this method as Multi-E i measurement.Another technique, the so-called ''repetition rate multiplication (RRM) method'', for reducing the dead time of TOF measurement has also been developed, 3,4) and recently its first implementation has been reported. 5) The RRM method is mainly applied to measurements with cold neutrons, such as those involving quasi-elastic neutron scattering. It requires several disk choppers to suppress the contamination of slow neutrons and produce the symmetric pulse shape of incident neutrons. On the other hand, Multi-E i m...

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Section: Lettersmentioning

confidence: 99%

First Demonstration of Novel Method for Inelastic Neutron Scattering Measurement Utilizing Multiple Incident Energies

et al. 2009

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“…Here we exemplify the phenomenon of a spin-Peierls transition for the linear-chain compound CuGeO 3 (Nishi et al, 1994), followed by a discussion of the three-dimensional compound CeRu 2 Al 10 , in which recently a dimerization has been suggested to occur (Robert et al, 2010). CuGeO 3 is a linear Cu 2+ (s i = 1/2) chain compound crystallizing in the orthorhombic space group P bmm with a = 4.81Å, b = 8.47Å, and c = 2.941Å at room temperature (Völlenkle et al, 1967). The coupling of the Cu 2+ ions positioned at (1/2,0,0) is strong along the c axis giving rise to physical properties typical of a onedimensional magnet.…”

Section: Spin-peierls Dimerizationmentioning

confidence: 99%

Magnetic Cluster Excitations

Fürrer

2010

Int. J. Mod. Phys. B

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Magnetic clusters, i.e., assemblies of a finite number (between two or three and several hundred) of interacting spin centers which are magnetically decoupled from their environment, can be found in many materials ranging from inorganic compounds, magnetic molecules, artificial metal structures formed on surfaces to metalloproteins. The magnetic excitation spectra in them are determined by the nature of the spin centers, the nature of the magnetic interactions, and the particular arrangement of the mutual interaction paths between the spin centers. Small clusters of up to four magnetic ions are ideal model systems to examine the fundamental magnetic interactions which are usually dominated by Heisenberg exchange, but often complemented by anisotropic and/or higher-order interactions. In large magnetic clusters which may potentially deal with a dozen or more spin centers, the possibility of novel many-body quantum states and quantum phenomena are in focus. In this review the necessary theoretical concepts and experimental techniques to study the magnetic cluster excitations and the resulting characteristic magnetic properties are introduced, followed by examples of small clusters demonstrating the enormous amount of detailed physical information which can be retrieved. The current understanding of the excitations and their physical interpretation in the molecular nanomagnets which represent large magnetic clusters is then presented, with an own section devoted to the subclass of the singlemolecule magnets which are distinguished by displaying quantum tunneling of the magnetization. Finally, some quantum many-body states are summarized which evolve in magnetic insulators characterized by built-in or field-induced magnetic clusters. The review concludes addressing future perspectives in the field of magnetic cluster excitations.

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“…4 Above 14 K, CuGeO 3 has an orthorhombic unit cell ͑originally the Pbmm space group has been proposed, [5][6][7] although recent measurements 8 suggest P2 1 2 1 2͒ with a long-range-order antiferromagnetic coupling. The low-temperature phase also shows an orthorhombic unit cell ͑Bbcm space group͒ but slightly distorted to give a ''dimer'' character to the chains.…”

Section: Introductionmentioning

confidence: 99%

Theoretical approach to the magnetostructural correlations in the spin-Peierls compoundCuGeO3

et al. 2000

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A theoretical density-functional study has been carried out to analyze the exchange coupling in the chains of CuGeO 3 using discrete models. The results show a good agreement with the experimental exchange coupling constant ͑J͒ together with a strong dependence of J with the Cu-O-Cu angle. The calculation of the J values for a distorted model indicates a larger degree of dimerization than those reported previously.

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Zur Kristallstruktur von CuGeO3

Cited by 195 publications

References 0 publications

First Demonstration of Novel Method for Inelastic Neutron Scattering Measurement Utilizing Multiple Incident Energies

First Demonstration of Novel Method for Inelastic Neutron Scattering Measurement Utilizing Multiple Incident Energies

Magnetic Cluster Excitations

Theoretical approach to the magnetostructural correlations in the spin-Peierls compoundCuGeO3

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