Magnetic phase transitions in an electroelastic model for magnetically ordered spin-crossover solids

Ogou, Saliou Bolarinwa; Oke, T.D.; Hontinfinde, F.; Boukheddaden, Kamel

doi:10.1103/physrevb.104.024431

Cited by 5 publications

(2 citation statements)

References 115 publications

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“…To date, although the symmetry breaking has been well described from the experimental point of view, the physical mechanisms behind the short-and long-range ordering over the lattice always raise curiosity. Some recent theoretical works investigated the intrinsic elastic frustration in the lattice and led to a rich variety of complex self-organizations of spin domains attributed to the symmetry breaking [61][62][63][64][67][68][69][70]. The present contribution aims to investigate the effect of symmetry breaking as well as the synergy between short-range and long-range interactions on the spin transition.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric self-organization accompanying a thermoinduced spin transition with symmetry breaking: Microscopic modeling

Slimani,

Boukheddaden

2023

Phys. Rev. B

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A microscopic elastic model allowing a symmetry breaking upon a spin transition is developed based on competing interactions between the nearest and next-nearest neighbors. The model yields a structurally degenerated high-spin state with a diamond-shaped cell and a nondegenerated low-spin state with a square-shaped cell. We investigated the effect of the symmetry change of the unit cell on the thermoinduced spin transition by monitoring the ratio of the elastic energies involved in the nearest and next-nearest neighbors. The simulations are performed on a deformable two-dimensional lattice made of spins S = ±1 (representing the high-spin and low-spin molecules) coupled with springs. The numerical resolution of the model is based on the Monte Carlo metropolis approach, running on spins and positions variables. The simulations of the thermoinduced spin transition disclose asymmetric thermal hysteresis loops with quite different domain distributions on the heating and cooling branches. The analysis of the magnetic and structural properties pointed out that the spin transition with symmetry breaking is dependent on the sign of the thermal gradient. We demonstrated that the nucleation and growth process of spin domains might contrast with the structural self-organization of the lattice according to the energetic contribution of the symmetry breaking. Indeed, the examination of the spatial organization aspects revealed that the structural and elastic anisotropy in the lattice hinders the long-range character of the intermolecular interactions. The lattice configurations show a labyrinthlike structure during a transition from high-symmetry to low-symmetry phases and a multidomain structure upon a transition in the other way around regardless of the spin state in both phases. Furthermore, we found that thermal fluctuations have a crucial role depending on the thermal gradient and on the direction of evolution of the symmetry (reducing or increasing). We demonstrated that stepped and even incomplete spin transitions could be obtained by adjusting the elastic contribution responsible for the symmetry breaking.

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Section: Introductionmentioning

confidence: 99%

Asymmetric self-organization accompanying a thermoinduced spin transition with symmetry breaking: Microscopic modeling

Slimani,

Boukheddaden

2023

Phys. Rev. B

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“…Due to difficulties related to numerical aspects and computational time, the elastic models have been applied in most cases to 2D samples [25][26][27][28][29]. Only very recently, several studies referred to 3D samples of different shapes [24,30,31].…”

Section: Introductionmentioning

confidence: 99%

Mechanoelastic simulations of monolayer lattices of spin crossover molecules on a substrate

et al. 2023

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In this paper, we discuss in the framework of a mechanoelastic model the electronic and mechanical behavior of a single layer of spin crossover molecules self-organized on a substrate. We consider the molecules situated in a face-centered-cubic structure interacting in between and with sites in the substrate by the way of connecting springs with given elastic constants. The main experimental results are reproduced, i.e., typical thermal transitions with their incompleteness of the hysteresis loop, residual fractions after low-temperature relaxations, cooperativity, or kinetic features. However, we prove that the simple model, implying fixed neighbors on the substrate for every spin crossover molecule, leads in some cases to unphysical situations, corresponding to unexpected large curvatures of the spin crossover layer. Therefore, to go further, we allow every spin crossover molecule to change its adsorption site on the substrate at every moment, by connecting to the closest molecules on the substrate. This approach, corroborated with the use of different densities of the sites on the substrate, allows us to simulate further experimental observations, such as the appearance of cracks inside the layer or periodic arrangements of apparent heights of spin crossover molecules on the layer leading to moiré patterns, for which experimental data are also provided.

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On the role of random bond in spin-crossover compounds

Gudyma

Yarema

2022

Appl Nanosci

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Magnetic phase transitions in an electroelastic model for magnetically ordered spin-crossover solids

Cited by 5 publications

References 115 publications

Asymmetric self-organization accompanying a thermoinduced spin transition with symmetry breaking: Microscopic modeling

Asymmetric self-organization accompanying a thermoinduced spin transition with symmetry breaking: Microscopic modeling

Mechanoelastic simulations of monolayer lattices of spin crossover molecules on a substrate

On the role of random bond in spin-crossover compounds

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