Speaker
Ms
Ursula Bengaard Hansen
(The Niels Bohr Institute)
Description
CoCl2·2D2O can be considered as an example of a one-dimensional magnetic system. The dominant magnetic interactions are ferromagnetic and couple nearest neighbour spins lying on chains oriented along the crystallographic c-axis. Weaker inter-chain interactions gives rise to an antiferromagnetic ordering below 17.2 K. When a magnetic field is applied along the easy axis CoCl2·2D2O has two metamagnetic transitions at Hc1 = 3.1 T and at Hc2 = 4.5 T. The transition at Hc1 is from the antiferromagnetic state (AF) to a ferrimagnetic state (FI) and the transition at Hc2 is to a ferromagnetic state (FE).
We have studied the phase ordering kinetics between the AF-phase and the FI-phase. It is possible to follow the domain coarsening of the AF long range order close to the phase boundary. The transition from short range to long range order is both temperature and field dependent and the corresponding timescales will vary from seconds to hours.
Here we will also present inelastic neutron scattering results and theoretical modelling of the spin wave spectrum of CoCl2·2D2O in the AF-, FI- and FE-phases. The conventional one spin flip spin waves are modified by a hybridisation with higher order spin flip excitations. In general excitations involving more than one spin-flip are normally to weak to be observed, but here we have the unique situation that they fall in the same energy range as the normal spin waves, which allows for the hybridisation to occur.
Primary author
Ms
Ursula Bengaard Hansen
(The Niels Bohr Institute)
