Ising-Like Model of Nanosize
Spin-Crossover Molecular Crystals
Iurii Gudyma and Artur Maksymov
1 Introduction
The transition coordination complexes with pseudo-octahedral (O h ) symmetry containing metal ion surrounded by nitrogen ligands under external stimuli show a socalled spin-crossover (SCO) transition between low-spin (LS) and high-spin (HS)
states with diamagnetic and paramagnetic properties, respectively. Such a transition
could be induced by weak external perturbations like temperature, pressure, light,
magnetic, or electrical field. The properties of spin states in SCO compounds are
determined by the redistribution of the electrons on the d-shell of the metal ion that
can be controlled by external driving force. Therefore, the LS and HS states of an SCO
compound demonstrate not only various magnetic properties but different optical,
structural, and electrical properties as well. Due to increased energy gap of the SCO
molecule in HS state, it is characterized by higher effective degeneracy and, therefore, by larger volume than the LS molecule. The different molecular volumes of HS
and LS states could provoke the breaking of equilibrium of local forces and cause the
localized elastic distortions. These effects could lead to the appearance of effective
long-range elastic interactions. Physically, to such a size, differences may, at least
partially, contribute the Jahn–Teller effect that also can be the reason for reduced
degeneracy of the spin state and can change the symmetry of SCO molecule [1].
However, the Jahn–Teller effect may be very different for various SCO compounds,
i.e., the complexes with 3d
4 , 3d
5 , and 3d
7 electronic configurations manifest weak
Jahn–Teller distortion for LS state, whereas the strong Jahn–Teller effect is observed
for HS and LS states of the compounds with 3d
4 and 3d
7 electronic configurations,
I. Gudyma (B)
Department of General Physics, Institute of Physical, Technical and Computer Sciences,
Yuriy Fedkovych Chernivtsi National University, 2 Kotsjubynskyi Str.,
Chernivtsi 58012, Ukraine
e-mail: yugudyma@gmail.com
A. Maksymov
Marian Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11,
30-348 Kraków, Poland
e-mail: maxyartur@gmail.com
© Springer Nature Switzerland AG 2021
O. Fesenko and L. Yatsenko (eds.), Nanomaterials and Nanocomposites,
Nanostructure Surfaces, and Their Applications, Springer Proceedings
in Physics 246, https://doi.org/10.1007/978-3-030-51905-6_11
143
Spin-Crossover Molecular Crystals
Iurii Gudyma and Artur Maksymov
1 Introduction
The transition coordination complexes with pseudo-octahedral (O h ) symmetry containing metal ion surrounded by nitrogen ligands under external stimuli show a socalled spin-crossover (SCO) transition between low-spin (LS) and high-spin (HS)
states with diamagnetic and paramagnetic properties, respectively. Such a transition
could be induced by weak external perturbations like temperature, pressure, light,
magnetic, or electrical field. The properties of spin states in SCO compounds are
determined by the redistribution of the electrons on the d-shell of the metal ion that
can be controlled by external driving force. Therefore, the LS and HS states of an SCO
compound demonstrate not only various magnetic properties but different optical,
structural, and electrical properties as well. Due to increased energy gap of the SCO
molecule in HS state, it is characterized by higher effective degeneracy and, therefore, by larger volume than the LS molecule. The different molecular volumes of HS
and LS states could provoke the breaking of equilibrium of local forces and cause the
localized elastic distortions. These effects could lead to the appearance of effective
long-range elastic interactions. Physically, to such a size, differences may, at least
partially, contribute the Jahn–Teller effect that also can be the reason for reduced
degeneracy of the spin state and can change the symmetry of SCO molecule [1].
However, the Jahn–Teller effect may be very different for various SCO compounds,
i.e., the complexes with 3d
4 , 3d
5 , and 3d
7 electronic configurations manifest weak
Jahn–Teller distortion for LS state, whereas the strong Jahn–Teller effect is observed
for HS and LS states of the compounds with 3d
4 and 3d
7 electronic configurations,
I. Gudyma (B)
Department of General Physics, Institute of Physical, Technical and Computer Sciences,
Yuriy Fedkovych Chernivtsi National University, 2 Kotsjubynskyi Str.,
Chernivtsi 58012, Ukraine
e-mail: yugudyma@gmail.com
A. Maksymov
Marian Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11,
30-348 Kraków, Poland
e-mail: maxyartur@gmail.com
© Springer Nature Switzerland AG 2021
O. Fesenko and L. Yatsenko (eds.), Nanomaterials and Nanocomposites,
Nanostructure Surfaces, and Their Applications, Springer Proceedings
in Physics 246, https://doi.org/10.1007/978-3-030-51905-6_11
143