From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) it is evident that the spin state transition behavior of Fe(ii) spin crossover coordination polymer crystallites at the surface differs from the bulk.
[Fe(Htrz)2(trz)](BF4) (Fe-triazole)
spin
crossover molecules show thermal, electrical, and optical switching
between high spin (HS) and low spin (LS) states, making them promising
candidates for molecular spintronics. The LS and HS transitions originate
from the electronic configurations of Fe(II) and are considered to
be diamagnetic and paramagnetic, respectively. The Fe(II) LS state
has six paired electrons in the ground states with no interaction
with the magnetic field and a diamagnetic behavior is usually observed.
While the bulk magnetic properties of Fe-triazole compounds are widely
studied by standard magnetometry techniques, their magnetic properties
at the individual level are missing. Here we use nitrogen vacancy
(NV) based magnetometry to study the magnetic properties of the Fe-triazole
LS state of nanoparticle clusters and individual nanorods of size
varying from 20 to 1000 nm. Scanning electron microscopy (SEM) and
Raman spectroscopy are performed to determine the size of the nanoparticles/nanorods
and to confirm their respective spin states. The magnetic field patterns
produced by the nanoparticles/nanorods are imaged by NV magnetic microscopy
as a function of applied magnetic field (up to 350 mT) and correlated
with SEM and Raman. We found that in most of the nanorods the LS state
is slightly paramagnetic, possibly originating from the surface oxidation
and/or the greater Fe(III) presence along the nanorods’ edges.
NV measurements on the Fe-triazole LS state nanoparticle clusters
revealed both diamagnetic and paramagnetic behavior. Our results highlight
the potential of NV quantum sensors to study the magnetic properties
of spin crossover molecules and molecular magnets.
Future molecular microelectronics require the electronic conductivity of the device to be tunable without impairing the voltage control of the molecules electronic properties. Here, we report the effect of creating...
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