2010/04/21 by O. Janson, Oleg Janson, A. A. Tsirlin +4
Biochemistry, Genetics and Molecular Biology · Energy · Physics and Astronomy · #Geomagnetism and Paleomagnetism Studies #Iron oxide chemistry and applications #Theoretical and Computational Physics #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.82.014424
published as Phys. Rev. B 82, 014424 (2010) · Dedicated to Stefan-Ludwig Drechsler on the occasion of his 60th birthday (9 pages, 6 figures)
arxiv created 2010/04/21 · openalex publication_date 2010/07/22 · arxiv updated 2010/07/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We unravel the magnetic nature of the mineral dioptase Cu6Si6O18\ensuremath⋅6H2O and show that strong quantum fluctuations can be realized in an essentially framework-type spin lattice of coupled chains, thus neither frustration nor geometric low dimensionality are prerequisites. We present a microscopic magnetic model for the green dioptase. Based on full-potential density-functional theory calculations, we find two relevant couplings in this system: an antiferromagnetic coupling Jc, forming spiral chains along the hexagonal c axis, and an interchain ferromagnetic coupling Jd within structural Cu2O6 dimers. To refine the Jc and Jd values and to confirm the proposed spin model, we perform quantum Monte Carlo simulations for the dioptase spin lattice. The derived magnetic susceptibility, the magnetic ground state, and the sublattice magnetization are in remarkably good agreement with the experimental data. The refined model parameters are Jc=78 K and Jd=\ensuremath-37 K with Jd/Jc\ensuremath≃\ensuremath-0.5. Despite the apparent three-dimensional features of the spin lattice and the lack of frustration, strong quantum fluctuations in the system are evidenced by a broad maximum in the magnetic susceptibility, a reduced value of the N'eel temperature TN\ensuremath≃15 K⪡Jc, and a low value of the sublattice magnetization m=0.55 \ensuremathμB. All these features should be ascribed to the low coordination number of 3 that outbalances the three-dimensional nature of the spin lattice.