We investigate the ground-state magnetic long-range order of quasi-one-dimensional quantum Heisenberg antiferromagnets for spin quantum numbers s=1/2 and s=1. We use the coupled cluster method to calculate the sublattice magnetization and its dependence on the inter-chain coupling J<Subscript>⊥</Subscript>. We find...</subscript>

We have investigated the ground state phase diagram of the 1D AF spin-<InlineEquation ID="Equ2"> <EquationSource Format="TEX">$\frac{1}{2}$</EquationSource> </InlineEquation> Heisenberg model with the staggered Dzyaloshinskii-Moriya (DM) interaction in an external uniform magnetic field H. We have used the exact diagonalization technique. In the absence of the uniform magnetic...</equationsource></inlineequation>

We report results of susceptibility χ and <Superscript>7</Superscript>Li NMR measurements on LiVSi<Subscript>2</Subscript>O<Subscript>6</Subscript>. The temperature dependence of the magnetic susceptibility χ(T) exhibits a broad maximum, typical for low-dimensional magnetic systems. Quantitatively it is in agreement with the expectation for an S=1 spin chain,...</subscript></subscript></superscript>

The energy gap of the 1D AF-Heisenberg model in the presence of both uniform (H) and staggered (h) magnetic fields is investigated using the exact diagonalization technique. The opening of the gap in the presence of a staggered field is found to scale with h<Superscript>ν</Superscript>, where ν=ν(H) is the critical...</superscript>

The exact solutions for the energy spectrum of the XX model with a periodic coupling and an external transverse magnetic field h are obtained. The diagonalization procedure is discussed, and analytical and numerical solutions are given. Using the solutions for period-two coupling, the free...