We study the one-dimensional isotropic spin-1 Heisenberg magnet with antiferromagnetic nearest-neighbor (nn) and next-nearest-neighbor (nnn) interactions by using the modified spin wave theory (MSWT). The ground state energy and the singlet-triplet energy gap are obtained for several values of...

We have studied the behavior of the energy gap of the 1D AF spin-<InlineEquation ID="Equ1"> <EquationSource Format="TEX">$\frac{1}{2}$</EquationSource> </InlineEquation> XXZ model in a transverse magnetic field (h) using the exact diagonalization technique. The ground state phase diagram consists of two spin-flop and paramagnetic phases. Using a modified finite-size scaling...</equationsource></inlineequation>

Excitations of the polaron types are investigated in the spin-1/2 quantum chain with XY exchange and Dzyaloshinsky-Moriya interaction, both coupled to acoustic vibrations of the substrate lattice. The study is carried out via Jordan-Wigner transformation with the help of which the spin chain is...

Motivated by field-theoretic predictions we investigate the stable excitations that exist in two characteristic gapped phases of a spin-1 model with Ising-like and single-ion anisotropies. The sine-Gordon theory indicates a region close to the phase boundary where a stable breather exists...

The critical behavior of the Ising chain with long-range ferromagnetic interactions decaying with distance r<Superscript>α</Superscript>, 1α2, is investigated using a numerically efficient transfer matrix (TM) method. Finite size approximations to the infinite chain are considered, in which both the number of spins and...</superscript>

The chemical selectivity and great sensitivity of the Extended X-ray Absorption Spectroscopy technique allowed the determination, in the paramagnetic phase, of the structural distortions induced by doping in the spin-Peierls CuGeO<Subscript>3</Subscript> compound. The distorted environments were analyzed as a function...</subscript>

We numerically investigate an S=1/2 spin model, in which two dimerized antiferromagnetic rings interact with each other ferromagnetically. It is shown that the order of the magnetoelastic transition is strongly affected by the interring coupling J<Subscript>⊥</Subscript> and there may exist a critical J<Subscript>⊥</Subscript> <Superscript>*</Superscript>...</superscript></subscript></subscript>