Physical Properties of 2D Spin-Crossover Solids from an Electro-Elastic Description: Effect of Shape, Size, and Spin-Distortion Interactions

Boukheddaden, Kamel; Slimani, Ahmed; Sy, Mouhamadou; Varret, F.; Oubouchou, Hassane; Traiche, Rachid

doi:10.1201/b19845-9

Cited by 5 publications

(5 citation statements)

References 155 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a result of our simple assumption, the thermal hysteresis moves according to the atomic surface/volume ratio, in very good agreement with the available experimental data of Volatron et al [64]. Since this pioneering work, the electroelastic model has been extended to incorporate the case of core-shell SCO nanoparticles, made of an active SCO core and an inert shell, where we investigated the detailed properties of the SCO core as a function of the elastic properties (rigidity, lattice parameter misfit, and size) of the shell [65][66][67][68][69][70]. It is worth mentioning that other groups investigated the problem of active core-shell SCO nanoparticles by considering hollow core-shell configurations, or by studying their vibrational properties as well the role of the elastic interface energy in the stability of the nanoparticles [71][72][73].…”

Section: Introductionsupporting

confidence: 79%

Magnetoelastic modeling of core-shell spin-crossover nanocomposites

2018

Self Cite

View full text Add to dashboard Cite

Spin-crossover (SCO) solids have been studied from magnetic and structural viewpoints under the form of powder, single crystals, and nanoparticles. Recently, an important progress made in chemistry allowed the design of spin-crossover nanocomposites, combining the properties of two types of spin-crossover solids having different properties, for example, different transition temperatures, ligand fields, etc. In this work, we sketch theoretical investigations based on an elastic description of a SCO nanocomposite, aiming to reproduce the experimental results of literature which exhibited two-step and even three-step spin transitions. Our results not only reproduce the experimental features but also allow a better understanding of the interplay between the elastic and electronic structures of the two components of the SCO nanocomposite. The obtained data offer serious possibilities of extensions to several configurations of nanocomposites according to the shape of the lattice and the relative sizes of the two components under study.

show abstract

Section: Introductionsupporting

confidence: 79%

Magnetoelastic modeling of core-shell spin-crossover nanocomposites

2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…This two-dimensional system was originally designed to mimic a core-shell structure formed by an inner spin-active core with spin crossover properties and an outer spin-inactive shell. The electroelastic model has shown its merits in the analysis of the thermal spin transition of spin crossover nanoparticles [46][47][48]. The additional insight gained through this study will be a useful step toward the elucidation of the structural relationship between the core and the shell properties.…”

Section: Introductionmentioning

confidence: 85%

“…The surrounding environment of the spin crossover materials, like the shell in a core/shell structure [29][30][31][32][33][34] offers the possibility to design and control the spin transition in a way that can go beyond naturally occurring in a free spin crossover nanosystem. Different approaches have been proposed to realize speculative ideas about the impact of the surrounding environment on the yielding of the spin crossover materials [38][39][40][41][42][43][44][45][46][47][48], but a detailed understanding of such relationship between the spin crossover core and the surrounding environment as well as their interplay with structural changes is challenging to unravel. The core-shell nanoparticles display a variety of complex phenomena as a marginal change in the transition temperature, a partial character of the spin transition as well as a significant lattice contraction through the spin transition which induces strain on the shell.…”

Section: Introductionmentioning

confidence: 99%

Structural synergy in a core-shell spin crossover nanoparticle investigated by an electroelastic model

2017

Self Cite

View full text Add to dashboard Cite

Understanding how surrounding environments act on the functional properties of switchable nano-objects across extended and multiple length scales is of growing interest in many areas of material science. Here, we examine in details, using a microscopic model, the interplay between the structural properties of an inert shell and a spin-active spin-crossover (SCO) core, composed of atoms which can switch thermally between the low-spin (LS) and high-spin (HS) states, a transition which is accompanied with a volume expansion. To come closer to realistic experimental data, we considered a shell having the lattice parameter of the HS state. Intensive Monte Carlo simulations, running on the spin states and atomic positions, are performed on the core-shell spin-crossover nanoparticle using an electroelastic model based on a compressible 2D lattice. A detailed analysis of the effect of the shell's size and rigidity on the magnetostructural properties of the core allows us to address the following issues: (i) the heteroelastic properties of the lattice induce a spatially inhomogeneous pressure (negative in the shell and positive in the core) which strongly distorts the lattice when the core is in the LS state, creating a visible spatial deflection of the shell/core interface; (ii) the thermally-induced first-order SCO transition of the core is significantly affected by the increase of the shell size, which lowers the transition temperature and reduces the thermal hysteresis width; (iii) the shell's rigidity dependence of the thermal hysteresis of the nanoparticle exhibited a resonance behavior when the shell's rigidity equals that of the core, a feature that is analyzed on the basis of acoustic impedance mismatch between the core and the shell. All these outcomes reflect the crucial influence of the surrounding environment on the structural properties of the nanoparticle and provide potentialities in the control of the bistability and cooperativity of the SCO nanoparticles by acting on their shell's rigidity.

show abstract

“…34,35 Indeed, this configuration corresponds to the shortest interface length, which is the one which minimizes the elastic energy resulting from the lattice parameter misfit between the two phases. Moreover, prior theoretical investigations on the spatiotemporal aspects of the spin transition, based on Monte-Carlo simulations, showed that the geometry of the single crystal controls the interface dynamics on the one hand, and the elastic energy is strongly correlated with the length of the interface, 24,25,36,37 on the other. This reasoning has however severe limitations, when the change in the unit cell between the LS and HS is anisotropic, as we have reported in the single crystal [{Fe(NCSe)(py) 2 } 2 (μ-bpypz)].…”

Section: The Velocity Fieldmentioning

confidence: 99%

“…The presented experimental spatiotemporal results derived from OM studies on the SCO single crystal, [Fe(2pytrz) 2 {Pd(CN) 4 }]•3H 2 O, are interpreted here using a reaction diffusion model, developed in the group 36,38 which takes into account the local change in the HS fraction, and its spatial variation along the spin transition process. In contrast with the previous homogeneous mean-field approach where the HS fraction (or the magnetization) only depended on temperature, here we extend this study to include time and space in the order parameter.…”

Section: Theoretical Descriptionmentioning

confidence: 99%

Interplay between a crystal's shape and spatiotemporal dynamics in a spin transition material

Fourati

Milin

Slimani

et al. 2018

Phys. Chem. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

We investigated by means of optical microscopy (OM) the spatiotemporal features of the thermo-induced spin transition of [Fe(2-pytrz)2{Pd(CN)4}]·3H2O (1) (2-pytrz = 4-(2-pyridyl)-1,2,4,4H-triazole) single crystals having two different shapes (triangle and rectangle). While magnetic and calorimetric measurements, performed on a polycrystalline material, showed the respective average heating and cooling transition temperatures of (Tdown1/2 ∼ 152 K, Tup1/2 ∼ 154 K) and (Tdown1/2 ∼ 160.0 K, Tup1/2 ∼ 163.5 K), OM studies performed on a unique single crystal revealed significantly different switching temperatures (Tdown1/2 ∼ 152 K and Tup1/2 ∼ 162 K). OM investigations showed an interface spreading over all crystals during the spin transition. Thanks to the color contrast between the low-spin (LS) and the high-spin (HS) states, we have been able to follow the real time dynamics of the spin transition between these two spin states, as well as access the thermal hysteresis loop of each single crystal. After image processing, the HS-LS interface's velocity was carefully estimated in the ranges [4.4-8.5] μm s-1 and [2.5-5.5] μm s-1 on cooling and heating, respectively. In addition, we found that the velocity of the interface is shape-dependent, and accelerates nearby the crystal's borders. Interestingly, we observed that during the propagation process, the interface optimizes its shape so as to minimize the excess of elastic energy arising from the lattice parameter misfit between the LS and HS phases. All of these original experimental results are well reproduced using a spatiotemporal model based on the description of the spin-crossover problem as a reaction diffusion phenomenon.

show abstract

Physical Properties of 2D Spin-Crossover Solids from an Electro-Elastic Description: Effect of Shape, Size, and Spin-Distortion Interactions

Cited by 5 publications

References 155 publications

Magnetoelastic modeling of core-shell spin-crossover nanocomposites

Magnetoelastic modeling of core-shell spin-crossover nanocomposites

Structural synergy in a core-shell spin crossover nanoparticle investigated by an electroelastic model

Interplay between a crystal's shape and spatiotemporal dynamics in a spin transition material

Contact Info

Product

Resources

About