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@PHDTHESIS{Shahed:1027489,
author = {Shahed, Hend},
title = {{E}lucidation of {B}arocaloric {E}ffect in {I}-4{S}pin
{C}rossover {C}ompounds},
volume = {630},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {FZJ-2024-03898},
isbn = {978-3-95806-758-5},
series = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
Umwelt / Energy $\&$ Environment},
pages = {x, 261},
year = {2024},
note = {Dissertation, RWTH Aachen University, 2024},
abstract = {The search for new materials for energy-efficient and
environmentally friendly refrigerant technologies is a key
challenge to replace conventional vapor compression
technology. An attractive alternative approach uses the
barocaloric refrigeration cycle, which is based on the
adiabatic temperature and isothermal entropy change of a
material upon tuning an external hydrostatic pressure.
Recently, spin crossover (SCO) compounds have been pointed
out as promising candidates, which exhibit large barocaloric
effects: large isothermal entropy changes have been reported
for some of these SCO compounds at fairly low hydrostatic
pressures (< 1.2 GPa). In SCO complexes, the central metal
ion switches between a low spin (LS) state at low
temperature / high pressure and a high spin (HS) state at
high temperature/low pressure. The LS to HS transition
involves an increase of the spin entropy, but the larger
part of the entropy change originates from changes in the
intramolecular vibrations. The fundamental understanding of
the nature of HS-LS transition and its effect on the
physical properties is still being explored fervently, and
in particular, the microscopic knowledge of the transition
mechanism is essential to tailor new materials. Although the
spin crossover is by essence a molecular scale phenomenon,
the large diversity in the spin transition characteristics
makes it challenging to predict. The spin transition is
controlled by cooperativity, which is a parameter that
describes to what extent the spin transition occurs
collectively across the material rather than in isolated
molecules. The exploration of the intricate interplay
between cooperativity and structural changes in the SCO
material is in the focus of this thesis. The compound
Fe(Pm-Bia)2(NCS)2, where Pm-Bia =
(N-(21-pyridylmethylene)-4-amino-bi-phenyl), is an ideal
candidate for these studies, as it exists in two different
polymorphs which exhibit SCO transitions with significantly
different characteristics.},
cin = {JCNS-2 / JARA-FIT},
cid = {I:(DE-Juel1)JCNS-2-20110106 / $I:(DE-82)080009_20140620$},
pnm = {899 - ohne Topic (POF4-899)},
pid = {G:(DE-HGF)POF4-899},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
doi = {10.34734/FZJ-2024-03898},
url = {https://juser.fz-juelich.de/record/1027489},
}