Wolter, A.U.B.; Wzietek, P.; Jerome, D.; Süllow, S.; Litterst, F.J.; Feyerherm, R.; Klauss, H.-H.: Observation of solitons in the S=1/2 antiferromagnetic chain [CuPM(NO3)2(H2O)2]_ by ^{13}C-NMR. Journal of Magnetism and Magnetic Materials 290-291 (2005), p. 302-305
10.1016/j.jmmm.2004.11.214
Abstract:
We present 13C-NMR investigations of the S = 1/2 antiferromagnetically coupled Heisenberg chain system [CuPM(NO3)2(H2O)2]n, (PM=C4N2H4=pyrimidine). For this material, as result of the Dzyaloshinskii¿Moriya interaction and an alternating g-tensor, the ground state is characterized by a giant static spin canting and an anisotropic magnetic field-induced spin excitation gap. We measured the spin¿lattice relaxation rate 1/T1 at three inequivalent carbon sites in the pyrimidine molecule as function of temperature. From these studies we deduce the magnetic excitation spectrum of copper pyrimidine dinitrate at a constant applied magnetic field of 9.3 T. The experimental data are discussed in context with recent ESR investigations, which have been interpreted in terms of breather, soliton and multi-particle excitations based on the quantum sine-Gordon field theory.