Research Topics and Teaching
Physical-inorganic chemistry. Synthesis, crystal
growth, optical spectroscopy, neutron scattering,
magnetic and excited-state properties of d - and
f - coordination compounds.
courses: Spectroscopy of coordination compounds, theory
of coordination compounds, molecular magnetism, neutron
scattering, inorganic materials, inorganic luminescence.
synthesis is combined with a variety of physical
techniques to study new inorganic materials. The optical
or magnetic properties are influenced and tuned by
chemical and structural variation.
upconversion in lanthanide and transition metal
NIR to VIS photon upconversion
processes and materials are extensively studied using a
variety of optical spectroscopic techniques. Both
rare-earth (RE) and transition-metal (TM) systems as
well as RE / TM combinations are explored. Competing
radiative and nonradiative excited state processes and
thus the light emitting processes are influenced by
chemical variation. Understanding the basic physical
mechanisms is the primary goal, but materials with high
upconversion yield and a potential for applications as
display phosphors or laser materials are also explored.
In collaboration with the group of C.W.E. van Eijk and
P. Dorenbos in Delft we are preparing and studying new
Ce3+ doped chloride, bromide and iodide
materials with potential applications in scintillation
detection of X-rays and g-rays.
and anisotropy interactions in spin clusters and single-molecule
The ground-state properties of exchange-coupled spin
clusters of transition metal and rare earth metal ions
are studied by magnetic measurements, EPR, inelastic
neutron scattering (INS) and theoretical modelling. INS
is a powerful tool in evaluating competing interactions
in larger clusters and in quantifying anisotropy
effects. The effects of competing interactions are also
studied in low-dimensional rare-earth halide systems
exhibiting magnetic order at cryogenic temperatures.
Neutron scattering experiments are performed at SINQ
(Villigen), ILL (Grenoble), HMI (Berlin) and ISIS
Quantum magnetisation processes
in KCuCl3, TlCuCl3 and NH4CuCl3
compounds exhibit ladder type structures with dominant
antiferromagnetic interactions within Cu2+
dimers and weaker coupling between the dimers.
Singlet-triplet excitations and their dispersion are
measured by single crystal INS studies with temperature
and a magnetic field as variables. At low temperatures
they show quantum critical phenomena. Recently we could
show that TlCuCl3 exhibits Bose-Einstein
Condensation behavior in an external magnetic field,
the first demonstration of this phenomenon in a