Abstract of Publication No. 407
S=1/2 dimer clusters are an excellent example
for singlet-triplet magnetic units which can be assembled into spin chains, spin ladders or
more complicated models
of quantum magnetism. The microscopic characterization of the resulting
ground-state and elementary excitations constitutes a lively research
field, involving neutron scattering at its forefront. In Cu2+ KCuCl3,
S=1/2 dimers are at the origin of well-defined singlet-triplet modes, which propagate in reciprocal space
above a finite energy gap of quantum nature. The spin symmetry of these collective
quantum excited states was investigated by polarized neutron scattering on single
crystals. Complete experimental results concerning the transversal and longitudinal
components of the triplet modes are presented in the context of an S=1/2 dimer model.
The assumption of spin isotropic Heisenberg interactions finds confirmation in the
polarization factors measured along the three crystallographic axes.