Using analytical series expansion by continuous unitary transformations we study the magnetic properties of a frustrated tetrahedral spin-<InlineEquation ID="Equ1"> <EquationSource Format="TEX">$\frac{1}{2}$</EquationSource> </InlineEquation> chain. Starting from the limit of isolated tetrahedra we analyze the evolution of the ground state energy and the elementary triplet...</equationsource></inlineequation>

The electronic structures (especially 4f states) of hexagonal and tetragonal erbium silicides are investigated within density functional theory. Contrary to previous theoretical studies on these compounds, Er 4f electrons are treated as valence state electrons, explicitly taking into account the...

We study the magnetic excitation spectrum of the spin-1 chain with Hamiltonian <Emphasis FontCategory="NonProportional">H=Σ<Subscript> i </Subscript> cos θ <Emphasis Type="Bold">S <Subscript> i </Subscript> · <Emphasis Type="Bold">S <Subscript> i+1</Subscript> + sin θ(<Emphasis Type="Bold">S <Subscript> i </Subscript> · <Emphasis Type="Bold">S <Subscript> i+1</Subscript>)<Superscript>2</Superscript>. We focus on the range 0 ≤ θ ≤ + π/4 where the spin chain is in the gapped Haldane phase. The excitation spectrum and static structure factor is studied...</superscript></subscript></emphasis></subscript></emphasis></subscript></emphasis></subscript></emphasis></subscript></emphasis>