The Jordan-Wigner transformation is applied to study the ground state properties and dimerization transition in the J<Subscript>1</Subscript>-J<Subscript>2</Subscript> XXZ chain. We consider different solutions of the mean-field approximation for the transformed Hamiltonian. Ground state energy and the static structure factor are compared...</subscript></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>

Ho<Subscript>0.1</Subscript>Ca<Subscript>0.9</Subscript>MnO<Subscript>3</S ubscript> is a canted antiferromagnet with the magnetic space group Pn′ma′. The magnetic structure is a superposition C<Subscript> x </Subscript>F<Subscript> y </Subscript>A<Subscript> z </Subscript> of the three types of order allowed in Pn′ma′. In the Ca-rich corner of the system Ho<Subscript>1−x </Subscript>Ca<Subscript> x </Subscript>MnO<Subscript>3</Subscript> the title compound has a strong magnetoelastic...</subscript></subscript></subscript></subscript></subscript></subscript><//s></subscript></subscript></subscript>

The magnetic properties of (La<Subscript>1 − x </Subscript>Sr<Subscript> x </Subscript>)MnO<Subscript>3</Subscript> crystals have been studied. The ac susceptibility χ=χ′ + iχ″ has been measured at frequencies ranging from 10 Hz to 1 000 Hz. The x=0.25 crystal shows a typical ferromagnetic behaviour with a dimensionless SI susceptibility of 6 below T...</subscript></subscript></subscript></subscript>