ELEMENTARY EXCITATIONS AND SPIN DYNAMICS IN NANOWIRE QUANTUM MAGNETS

We investigate the elementary excitations and magnetization dynamics of the recently synthesized single-chain magnets, which consist of Mn and Ni ions, and some related systems, using the numerical exact diagonalization of finite-size clusters and the density matrix renormalization group method. It is found that, as the easy-axis anisotropy D increases, a crossover of the lowest-lying elementary excitation should exist between the spin wave and Ising-like excitations. For the realistic trimer single-chain magnet, we estimate several crossover temperatures. In addition we predict that a magnetization plateau at 2/3 of the saturation magnetization would appear in the (s, S) = (1, 2) spin-alternating chain. The phase diagram of the plateau is also presented.