https://doi.org/10.1007/s100510050855
Analytical solution of 1D Ising-like systems modified by weak long range interaction
Application to spin crossover compounds
1
Laboratoire de Magnétisme et d'Optique (CNRS-URA 1531) ,
Université de Versailles,
78035 Versailles Cedex, France
2
Institut für Anorganische Chemie und Analytische Chemie, Johannes
Gutenberg-Universität Mainz, 55090 Mainz, Germany
Corresponding author: a spiering@iacgu7.chemie.uni-mainz.de
Received:
26
November
1998
Published online: 15 July 1999
It is well-known that 1D systems with only nearest neighbour interaction
exhibit no phase transition. It is shown that
the presence of a small long range interaction treated
by the mean field approximation in addition to strong nearest neighbour
interaction gives rise to hysteresis curves of large width. This situation
is believed to exist in spin crossover systems where by the deformation
of the spin changing molecules,
an elastic coupling leads to a long range
interaction, and strong bonding between the molecules in a
chain compound leads to large values for nearest neighbour interaction constants. For this
interaction scheme an analytical solution has been derived and the interplay
between these two types of interaction is discussed on the basis of
experimental data of the chain compound
which exhibits a very large hysteresis of 50 K
above RT at 370 K.
The width and shape of the hysteresis
loop depend on the balance between long
and short range interaction.
For short range interaction energies much larger
than the transition
temperature
the hysteresis
width is determined by the long range interaction alone.
PACS: 64.30.+t – Equations of state of specific substances / 64.60.Cn – Order-disorder transformations; statistical mechanics of model systems
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999