Excitations in the paramagnetic phase of dioptase
‘The gem-stone mineral green dioptase, CuSiO3.H2O, crystallizes in the space group R3. Hexagonal rings of silica tetrahedra interconnect the magnetic Cu2+ ions with spin 1/2. ‘The Cu2+ are surrounded by axially-elongated oxygen octahedra [1, 2]. ‘The copper-oxygen network forms corner-sharing spirals along the hexagonal c-axis, neighbouring copper sites along the spiral are displaced by c/3. ‘The spiral chains have a honeycomb arrangement in the ab-plane. Th‘e small amount of entropy involved in the phase transition, and the small size of the ordered moment point to dominant quantum flƒuctuations and a close-by spin-liquid phase. Moreover, dioptase is quasi-one dimensional with dominant AF-intrachain interactions. We therefore wonder if the broadened features in the inelastic spectra are related to remainders of spinon-continua as in the ordered phase of KCuF3 (TN =39 K). To prove this idea we propose to explore the inelastic spectrum above the Neel temperature, at about 20 K, up to twice the 1D-spin-wave zone boundary energy (11meV) on IN20.
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SAFIULINA Irina; ENDERLE Mechthild and HANSEN Ursula Bengaard. (2020). Excitations in the paramagnetic phase of dioptase. Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.4-05-764
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