Abstract
Orthorhombic copper polysilicate, CuSiO3, is isotypic to the spin-Peierls compound CuGeO3 and represents a further example of a quasi-one-dimensional spin = 1/2 antiferromagnetic Heisenberg chain system. This is a representation of the first Raman and IR/FIR spectra for CuSiO3, measured at room temperature on polycrystalline samples. A comparison of the optical phonons, predicted by a factor group analysis, with those observed for the CuGeO3 prototype, is presented. A mode assignment for the silicate is given. Surface effects due to a very small crystallite size may cause additional broad bands observed in the Raman spectrum of CuSiO3. From the analysis of the Davydov doublet an intralayer-to-interlayer bond strength of about 40 is derived for the silicate, which is about 20% lower than for the isotypic germanate, allowing for different magnetic responses at low temperature.
Highlights
Low-dimensional quantum spin systems are of considerable theoretical and experimental interest
The crystal structure of copper polygermanate consists of two types of chains which running down the shortest translation period: einer single chains of GeO4 tetrahedra are connected by chains of edge-sharing CuO4+2 “octahedra” [4] [5], which are in reality due to the Jahn-Teller effect strongly elongated and distorted tetragonal dipyramids
The Raman spectrum of CuSiO3 was recorded with a DILOR LabRAM spectrometer, using a Nd-YAG-laser with frequency doubler (λ = 532 nm) as an exciting source, and the spectrum of CuGeO3 with a Raman FRA 106 modul attached to a BRUKER IFS 66v interferometer, using once again a Nd-YAG-laser, but with λ = 1064 nm
Summary
Low-dimensional quantum spin systems are of considerable theoretical and experimental interest. The crystal structure of copper polygermanate consists of two types of chains which running down the shortest translation period: einer single chains of GeO4 tetrahedra are connected by chains of edge-sharing CuO4+2 “octahedra” [4] [5], which are in reality due to the Jahn-Teller effect strongly elongated and distorted tetragonal dipyramids. Because of this the magnetic chains are formed by ladders of CuO2 squares. Bond length (Å) 2.926 (7) x 2 1.941 (4) x 4 1.640 (7) x 2 1.582 (7) x 2 2.7549 (8) x 2 1.9326 (7) x 4 1.7730 (8) x 2 1.7322 (10) x 2
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