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Magnetic Ground State and Magnetic Excitations in Black Dioptase Cu6Si6O18



A. Podlesnyak, O. Prokhnenko, S. E. Nikitin, A. I. Kolesnikov, M. Matsuda, Sachith E. Dissanayake, Timothy R Prisk, H. Nojiri, I. F. Diaz-Ortega, L. M. Anovitz


The low-temperature magnetic properties and magnetic structure of fully dehydrated black dioptase Cu6Si6O18 have been studied by single-crystal neutron diffraction and magnetization measurements in magnetic fields up to 30 T. The intrachain Jc and interchain Jab interactions as well as the anisotropy of the exchange coupling Jc have been determined using inelastic neutron scattering technique. Zero-field antiferromagnetic order at TN = 6.7 K can be described by a commensurate propagation vector of K = (0,0,3/2) with respect to the hexagonal R3:H unit cell. The Cu magnetic moments are aligned antiferromagnetically along the c-axis with about 12° tilt and are coupled ferromagnetically between the chains. The high-field magnetization measurements provide strong evidence for the presence of a spin-flop phase above 8 T. We found that Jc in black dioptase is significantly increased, while Jab is much weaker, compared to its counterpart, green dioptase Cu6[Si6O18]&#82266H2O. We suggest that black dioptase behaves like a nearly ideal spiral S=1/2 antiferromagnetic Heisenberg chain with enhanced quantum fluctuations and weak spinon confinement Jab/Jc 0.02.
Physical Review B


Podlesnyak, A. , Prokhnenko, O. , Nikitin, S. , Kolesnikov, A. , Matsuda, M. , Dissanayake, S. , Prisk, T. , Nojiri, H. , Diaz-Ortega, I. and Anovitz, L. (2019), Magnetic Ground State and Magnetic Excitations in Black Dioptase Cu<sub>6</sub>Si<sub>6</sub>O<sub>18</sub>, Physical Review B, [online], (Accessed April 23, 2024)
Created October 31, 2019, Updated October 12, 2021