arXiv:cond-mat/9906273 · Physical review. B, Condensed matter
High magnetic-field ESR in the Haldane spin chains NENP and NINO
M. Sieling, U. Löw, B. Wolf, S. Schmidt, Sergei A. Zvyagin, B. Lüthi
Abstract
We present electron spin resonance experiments in the one-dimensional antiferromagnetic $S=1$ spin chains NENP and NINO in pulsed magnetic fields up to 50 T. The measured field dependence of the quantum energy gap for $B||b$ is analyzed using the exact diagonalization method and the density matrix renormalization group method. A staggered anisotropy term $(\ensuremath{-}{1)}^{i}{d(S}_{i}^{x}{S}_{i}^{z}{+S}_{i}^{z}{S}_{i}^{x})$ was considered in addition to a staggered field term $(\ensuremath{-}{1)}^{i}{S}_{i}^{x}{B}_{\mathrm{st}}.$ We show that the spin dynamics in high magnetic fields strongly depends on the orthorhombic anisotropy E.