Abstract
We synthesized single crystals of composition and investigated their quantum magnetic properties. The crystal structure is closely related to that of the quasi-two-dimensional (2D) dimerized magnet also known as Han purple. has a singlet ground state with an excitation gap of K. The magnetization curves for two different field directions almost perfectly coincide when normalized by the factor except for a small jump anomaly for a magnetic field perpendicular to the axis. The magnetization curve with a nonlinear slope above the critical field is in excellent agreement with exact-diagonalization calculations based on a 2D coupled spin-dimer model. Individual exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate a 2D exchange network and weak frustration between interdimer exchange interactions, supported by weak spin-lattice coupling implied from our magnetostriction data. The magnetic-field-induced spin ordering in is described as the quasi-2D Bose-Einstein condensation of triplets.
- Received 15 May 2016
- Revised 27 June 2016
DOI:https://doi.org/10.1103/PhysRevB.94.094421
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