Optical Techniques for Systems with Competing Interactions

Abstract

Optical spectroscopy and Raman scattering can be used to probe all the relevant degrees of freedom in a solid. In this chapter, we present an overview of the elementary and collective excitations accessible in compounds where spin, orbital, and lattice degrees of freedom compete strongly. For illustration, we will focus in particular on the magnetic response of the weakly coupled spin-tetrahedron system Cu2Te2O5(Br,Cl)2, on optical phonons in the highly frustrated pyrochlore antiferromagnets CdCr2O4 and ZnCr2O4, and on exciton-magnon excitations in the quasi-one-dimensional spin-1/2 Heisenberg antiferromagnet KCuF3.