(5FAP)2CuCl4
(5FAP)2CuCl4 is another quantum magnet composed of S=1/2 antiferromagnetic dimers. However, one thing does distinguish it from the others: here the dimers naturally form a weakly coupled layers. Thus, the problems of "magnetic Bose-Einstein condensation" type can be studied in a two-dimensional setting with this material.
D. Blosser, M. Horvatić, R. Bewley, S. Gvasaliya and A. Zheludev, Dynamics and field-induced order in the layered spin S=1/2 dimer system (C5H6N2F)2CuCl4, external pagearXiv:1906.00602; external pagePhys. Rev. Materials 3, 074410 (2019)
T. Hong, S. N. Gvasaliya, S. Herringer, M. M. Turnbull, C. P. Landee, L.-P. Regnault, M. Boehm, and A. Zheludev, Dynamics of the two-dimensional S=1/2 dimer system (C5H6N2F)2CuCl4, external pagePhys. Rev. B 83, 052401 (2011)