Date of Original Version
The spin-Peierls transition is considered as a progressive spin-lattice dimerization occurring below a transition temperature in a system of one-dimensional antiferromagnetic Heisenberg chains. In the simplest theories, the transition is second order and the ground state is a singlet with a magnetic gap. The historical origins and theoretical development of the concept are examined. Magnetic susceptibility and EPR measurements on the π-donor-acceptor compounds TTF·MS4C4(CF3)4 (M=Cu, Au; TTF is tetrathiafulvalene) are reported. These compounds exhibit clearly the characteristics of the spin-Peierls transition in reasonably good agreement with a mean-field theory. The susceptibility of each compound has a broad maximum near 50 K, while the transitions occur at 12 and 2.1 K for M=Cu and Au, respectively. EPR linewidth observations over a broad temperature range are examined. Areas for further experimental and theoretical work are indicated, and a critical comparison is made of related observations on other materials.
Jacobs, I. S., Bray, J. W., Hart, H. R., Interrrante, L. V., Kasper, J. S., Watkins, G. D., Prober, D. E., & Bonner, J. C. (1976). Phys. Rev. B, 14(7), 3036-3051. doi: 10.1103/PhysRevB.14.3036
Available at: http://dx.doi.org/10.1103/PhysRevB.14.3036