Date of Original Version
Magnetic-susceptibility and EPR measurements are reported which provide the first unambiguous evidence for a spin-Peierls transition in a system of linear one-dimensional antiferromagnetic Heisenberg chains. The material studied is TTFCuS4C4(CF3)4 (TFF stands for tetrathiafulvalinium). At 12 K, the spin-lattice system undergoes a second-order phase transition to a singlet ground state.
J. W. Bray, H. R. Hart, Jr., L. V. Interrante, I. S. Jacobs, J. S. Kasper, G. D. Watkins, S. H. Wee, and Jill C. Bonner Observation of a Spin-Peierls Transition in a Heisenberg Antiferromagnetic Linear-Chain System. Phys. Rev. Lett. 35 (1975), 744. Available at: http://dx.doi.org/10.1103/PhysRevLett.35.744