The high-field magnetic properties and magnetic order of the gem mineral green dioptase Cu6[Si6O18]⋅6H2O have been studied by means of single-crystal neutron diffraction in magnetic fields up to 21T and magnetization measurements up to 30T. In zero field, the Cu2+-moments in the antiferromagnetic chains are oriented along the c-axis with a small off-axis tilt. For a field applied parallel to the c-axis, the magnetization shows a spin-flop-like transition at B∗=12.2T at 1.5K. Neutron diffraction experiments show a smooth behavior in the intensities of the magnetic reflections without any change in the periodicity of the magnetic structure. Bulk and microscopic observations are well described by a model of ferromagnetically coupled antiferromagnetic XXZ spin-21 chains, taking into account a change of the local easy-axis direction. We demonstrate that the magnetic structure evolves smoothly from a deformed N\'eel state at low fields to a deformed spin-flop state in a high field via a strong crossover around B∗. The results are generalized for different values of interchain coupling and spin anisotropy.
@article{arxiv.2101.08555,
title = {High-field spin-flop state in green dioptase},
author = {O. Prokhnenko and G. Marmorini and S. E. Nikitin and D. Yamamoto and A. Gazizulina and M. Bartkowiak and A. N. Ponomaryov and S. A. Zvyagin and H. Nojiri and I. F. Díaz-Ortega and L. M. Anovitz and A. I. Kolesnikov and A. Podlesnyak},
journal= {arXiv preprint arXiv:2101.08555},
year = {2021}
}