The cooperative spin transition in [FexZn1 − x(ptz)6](BF4)2: I. Elastic properties — an oriented sample rotation study by Brillouin spectroscopy

Jung, Johann; Bruchhäuser, F.; Feile, R.; Spiering, H.; Gütlich, Philipp

doi:10.1007/s002570050156

Cited by 55 publications

(43 citation statements)

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“…Indeed, the variations of the equilibrium intermolecular distance and bond stiffness upon the LS → HS transition result in volume and bulk modulus changes, which are major experimental features of the spin transition. The values of the intermolecular interactions A ij in the HS and LS phases can be derived from the bulk modulus, E ≈ A 0 R [32], which in spin-crossover solids has been estimated by Brillouin spectroscopy in the range 5-20 GPa [27,33]. Accordingly, an order of magnitude of the stiffness constant A 0 could be obtained by considering the elongation of a cubic cell using a 3D lattice, with lattice parameter a, submitted to an uniaxial stress, and neglecting the transversal effects.…”

Section: Calculation Detailsmentioning

confidence: 99%

“…However, a gradual transition described by a simple Boltzmann distribution between the two states * ahmed@tcl.t.u-tokyo.ac.jp † kbo@physique.uvsq.fr is generally obtained in highly diluted crystals, considered as noncooperative systems [15]. Several research works have focused on the contribution of the elastic interactions from the theoretical [16][17][18][19][20][21][22][23][24][25][26] and experimental points of view [27,28]. In fact, theoretical models devoted to the investigation of the spin transition simulate quite well the experimental phase diagrams; however, some limitations emerge when the spatiotemporal aspects of the transition are considered.…”

Section: Introductionmentioning

confidence: 99%

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Effect of intermolecular interactions on the nucleation, growth, and propagation of like-spin domains in spin-crossover materials

2015

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The nucleation, growth, and propagation of like-spin domains in spin-crossover materials was investigated during the relaxation process of a metastable HS state at low temperature using an electroelastic model running on a deformable two-dimensional square lattice. We distinguish the onset of patterns formation of low-spin domain as the intermolecular interaction is increased, passing successively through random dispersion to clustering pattern and ending up with an impressive single macroscopic domain growth. Attaining and maintaining a single-domain configuration through the transition is attributed to the long-range character of interactions. Qualitative investigation of the elastic energy, of the propagation of the low-spin domain, and of the displacement field are presented. We demonstrate that as the intermolecular interaction increases the propagation of the like-spin domain slowdown. The deformations are believed as the prolonged effect of the intermolecular interactions that are at the origin of the onset of dispersed, poly-, and single-domain nucleation. Spatial autocorrelation of the deformations analysis based on Moran's I index is used. We demonstrate that at short distance significant spatially autocorrelated patterns are detected, and the extent of the autocorrelation decreases with the distance.

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Section: Calculation Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of intermolecular interactions on the nucleation, growth, and propagation of like-spin domains in spin-crossover materials

2015

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“…The volume change at the transition induces differences in the bulk moduli of the LT and HT phases. When analyzed within the frame of the Grüneisen approximation, considering the quadratic dependence of the bulk modulus B on the Debye frequency (or temperature), it leads to the following relation34:…”

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confidence: 99%

Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4

Yangui

et al. 2015

Sci Rep

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The dynamics of the thermally induced first-order structural phase transition in a high-quality single crystal of the organic-inorganic perovskite (C12H25NH3)2PbI4 was investigated by optical microscopy. The propagation of the straight phase front (habit plane) during the phase transition along the cooling and heating pathways of the thermal hysteresis was observed. The thermochromic character of the transition allowed monitoring of the thermal dependence of average optical density and aided the visualization of the interface propagation. The thermal hysteresis loop is 10 K wide, and the interface velocity is constant at V ≈ 1.6 mm s–1. The transition is accompanied with sizeable change in crystal size, with elongation of ~6% along the b axis and compression of ~ –2% along the a axis, in excellent agreement with previously reported X-ray diffraction data. The progression of the habit plane is at least 160 times faster than in spin-crossover materials, and opens new prospects for organic-inorganic perovskites as solid switching materials. Moreover, the crystals of (C12H25NH3)2PbI4 are unusually mechanically robust and present excellent resilience to thermal cycling. These hitherto unrecognized properties turn this and possibly similar hybrid perovskites into perspective candidates as active medium for microscopic actuation.

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“…This pressure effectively interacts with all molecules in the crystal (independent of distances) by the same strength. In fact, the contribution of the elastic interactions has been studied in detail both theoretically [18,19] and experimentally by measuring elastic constants by Brillouin spectroscopy [20] and temperature dependent X-ray diffraction [21]. It turns out that the interaction constants obtained from transition curves of the metal dilution series in [Fe x Zn 1 − x (propyltetrazole) 6 ](BF 4 ) 2 essentially are explained by the elasticity theory (about 80%), where the molecules are treated as point defects and the lattice as a homogeneous medium [22,23].…”

Section: Introductionmentioning

confidence: 99%

Correlations of the distribution of spin states in spin crossover compounds

Spiering

Kohlhaas

Romstedt

et al. 1999

Coordination Chemistry Reviews

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136

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The cooperative spin transition in [FexZn1 − x(ptz)6](BF4)2: I. Elastic properties — an oriented sample rotation study by Brillouin spectroscopy

Cited by 55 publications

References 2 publications

Effect of intermolecular interactions on the nucleation, growth, and propagation of like-spin domains in spin-crossover materials

Effect of intermolecular interactions on the nucleation, growth, and propagation of like-spin domains in spin-crossover materials

Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4

Correlations of the distribution of spin states in spin crossover compounds

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