Spin cross-over and the Mössbauer emission spectrum of cobalt-57-labelled di-isothiocyanatobis(1,10-phenanthroline)-iron(II) and -cobalt(II)

Pressure-induced multi-step and self-organized spin states in an electro-elastic model for spin-crossover solids

“…It is interesting to remark that the Hamiltonian ( 27) with homogeneous bond lengths can be developed and re-written under the form of a special Ising model. Replacing the instantaneous distance r ij by x eq , given in eqn (30) and inserting the expressions of the lattice bond lengths (2), leads after some longer calculations to the following Ising-like model,…”

“…In cooperative spin-crossover solids, the nucleation and the growth of the spin states during the spin transition arise from local volume expansions taking place at several regions in the lattice and their propagation is caused by their interference in the whole lattice (due to the long-range character of the emerging elastic interactions) resulting in a global volume expansion accompanied by significant deformation of the crystal lattice, which produces inhomogeneous mechanical stresses inside the system leading in some extreme cases to the breakdown of the crystals at the transition. From the experimental point of view, the investigations on the SCO molecular complexes benefited from a large panel of techniques, like x-ray diffraction, optical microscopy, colorimetry, Mössbauer and uv-visible spectroscopies, reflectively, photoluminescence [22,24,[27][28][29][30][31][32][33][34][35][36][37][38][39] etc showing many features in the thermal properties of these materials such as gradual transition which follows the Boltzmann statistics, first-order transition with hysteresis, incomplete spin transitions with residual HS fraction at low-temperature, two-and multi-step transitions characterized by intermediate plateaus in which the spin states are self-organized [40][41][42][43][44][45][46][47][48] etc. Theoretically, the mechanism behind all these behaviors are often investigated using macroscopic or microscopic descriptions such as the regular solutions model [49,50] based on a thermodynamical approach where the interaction parameters related to the weak intermolecular interactions in iron(III) compounds are introduced in a phenomenological way, continuous medium model [51] which do not explicitly describe the particular micro-organization of the HS and the LS domains, and also Ising-like models [52][53][54]…”

Hexagonal-Shaped Spin Crossover Nanoparticles Studied by Ising-Like Model Solved by Local Mean Field Approximation

“…The change in spin state is accompanied by significant changes in the color, volume, magnetic state, and electrical conductivity of the compound, which can be observed by using different characterization techniques (such as magnetometry, Mössbauer, optical spectroscopy, X-ray diffraction, and calorimetry) [20][21][22][23][24].…”

Dance of Interference Patterns during the Spin Transition of a Single Crystal

“…The large volume and electronic changes accompanying the spin transition affect significantly the physical properties of the SCO materials, such as color and mechanical properties. Due to this wide range of changes, several experimental techniques were used to monitor and study the SCO phenomenon, such as differential scanning calorimetry, − magnetometry, − X-ray diffraction, − Mössbauer spectroscopy, , diffuse reflectivity, , quite recently, optical microscopy (OM), − and, very recently, resonant ultrasonic spectroscopy in a ferroelastic SCO compound.…”