Magnetic solitons investigated by NMR and ESR

Experimental Evidence for Soliton Pairing in TMMC below T N

“…The transition from the 1D to the 3D ordered phase was checked from the shape of the NMR spectrum: below TN(H) there occurs a characteristic splitting of lines. Above TN, in the 1D regime, the T1 data show a universal exponential decrease with respect to HIT as reported in the literature [14,15]. Below TN, however, we found that the behaviour of T, is just reverse: instead of a decrease there occurs a much steeper increase which is also exponential in HIT, but no longer universal for different fields (see fig.…”

“…The spin-lattice relaxation rate probes the local fluctuations of the hyperfine field which can be expressed in terms of the integrated dynamic structure factor [15]: UT1--1 dqA;S"(q, 0). It was shown [14,151 that within the investigated regimes of H and T the dominating contribution results from the soliton-induced sublattice flips, giving rise to large fluctuations of the staggered spin component S&.…”

“…The sublattice flipping rate r = 4n, zj , is proportional to the density n, = m d w e x p [-E,lkB TI and to the average velocity gn = c q m of the x-kink solitons. In terms of field and temperature this rate can be expressed by [15] W/kB c: a,H exp [-a,H/T]. The parameter a, represents a measure for the activation energy of a static x-kink E i k ~ a,H, which can directly be obtained from experiment, and hmc = gpBH 2 : a,HkB/S.…”

Nonlinear dynamics of the TMMC chain

“…A simple sine-Gordon theory explains these results for fields under 40 kOe; there T −1 1 decreases with the field. For stronger fields the increase of T −1 1 suggests a deviation from the sine-Gordon theory since it may be interpreted by a switching of the roles of the magnetic field and the anisotropy [2]. Consequently, two extreme cases are predicted to occur as regards low-temperature excitations: first, a soliton consisting in a rotation of the spins up to an angle π from an antiferromagnetic or a spin-flop order in a plane perpendicular to the chain direction (x-y soliton), and second, an analogous rotation but now in a plane containing the chain direction (y-z soliton).…”

“…Literature pertinent to magnetic excitations in this system can be found in [2][3][4][5][6][7][8][9]. We are interested in the analysis of the coherent and chaotic structures of the TMMC chain.…”