Magnetic excitations in the quasi-one-dimensional singlet ground-state systems CsFeBr3 and CsFeCl3 under hydrostatic pressure: a neutron scattering study

The quasi-one-dimensional magnets AFeX3 have aroused much interest in recent years due to their unique magnetic properties. It has been shown that the magnetic excitations in linear chain systems with half-integer and integer spin value differ fundamentally. Haldane conjectured that an energy gap will arise in linear chain systems with integer spin. The magnetic systems studied in this thesis: CsFeBr3 and CsFeCl3 are linear chain compounds which have a singlet ground state and are described by an effective spin S=1 formalism. [Continues.]