Structural analysis ofCuGeO3: Relation between nuclear structure and magnetic interaction

Abstract

The structure of CuGeO 3 has been analyzed by means of x-ray and neutron single-crystal diffraction as a function of temperature. There is a pronounced temperature dependency of the atomic positions in the hightemperature Pbmm phase. The observed deformation scheme on cooling from 295 to 20 K may be characterized by a rotation of the Cu͓O͑2͔͒ 2 ribbons around the c axis. It is related to the distortion below the spin-Peierls transition, and has an impact on the magnetic interaction parameter J. For the distorted structure in the spin-Peierls phase, based on a large set of superstructure reflections, we qualitatively confirm the proposed model ͑space group Bbcm͒ with a slightly different direction of the oxygen displacements. A computation of J reveals that its splitting in the spin-Peierls phase is dominated by the modulation of the Cu-O-Cu bond angle.

Decorated Shastry-Sutherland lattice in the spin-12magnet CdCu2(BO3)Janson1, Rousochatzakis2, Tsirlin3 et al. 2012Phys. Rev. B

“…Using a closely related approach, Braden et al 30 Here, we try to apply this phenomenological approach and estimate the respective exchange integrals. The intradimer Cu(1)-O-Cu(1) angle in CdCu 2 (BO 3 ) 2 is 98.2 • , only slightly exceeding 97 • .…”

Anisotropic superexchange for nearest and next-nearest coppers in chain, ladder, and lamellar cuprates

“…1) the leading order magnetic exchange is small. Therefore, higher-order perturbation processes, as well as details of the structure like the presence of side groups 11,12 have a significant contribution. For the same reason, next-nearest-neighbor CuCu couplings are expected to be much more important than in the case of the linear Cu-Cu bond configuration.…”

The random mass Dirac model and long-range correlations on an integrated optical platform

“…For example, in the spin-Peierls material CuGeO 3 , the angle of the Cu À O À Cu bond has a crucial impact on the coupling between the spin carrying Cu-atoms J, as well as on the dimerization strength d (ref. 26). By tuning the corresponding parameters k and s along the transverse axis of the waveguide lattice, one could investigate the impact of a deformation of the chain due to external effects, such as strain.…”

“…For specific compounds and doping conditions, certain predictions of the model, such as phase transitions or long-range ordering, have been experimentally tested, either by the measurement of macroscopic quantities 22,24,25 or by scattering techniques 23,[26][27][28] . However, some configurations are difficult to investigate experimentally, such as the impact of boundaries 29 or spatial variations in the coupling or dimerization strength.…”