Publisher Summary This chapter discusses percolation theory as well as spin-glass
phenomena, the former of which is used to understand subjects as diverse as fluid flow in …

We discuss the nature and sequence of phase transitions in two-dimensional systems with
continuous degeneracy, in which other factors must be taken into account in addition to the …

We study the ground-state and low-energy properties of classical vector spin models with
nearest-neighbor antiferromagnetic interactions on a class of geometrically frustrated …

The quantum pyrochlore antiferromagnet is studied by perturbative expansions and exact
diagonalization of small clusters. We find that the ground state is a spin-liquid state: The spin …

A group-symmetry analysis of the low-lying levels of the spin-1/2 kagomé Heisenberg
antiferromagnet is performed for small samples up to N= 27. This approach allows one to …

In recent work, we argued that a particular algebraic spin liquid (ASL) may be the ground
state of the S= 1/2 kagome lattice Heisenberg antiferromagnet. Furthermore, this state, which …

We study the exact low energy spectra of the spin 1/2 Heisenberg antiferromagnet on small
samples of the kagomé lattice of up to N= 36 sites. In agreement with the conclusions of …

Starting from a modified version of the S= 1/2 Kagome antiferromagnet to emphasize the
role of elementary triangles, an effective Hamiltonian involving spin and chirality variables is …

Static and dynamic magnetic correlations in the geometrically frustrated pyrochlore
antiferromagnet Y 2 M o 2 O 7 have been studied using neutron scattering. The material is …

This book was written from lectures given to MSc students following the'Matter and
Radiation'course at the University of Grenoble I. Although magnetism and superconductivity …