Thermally driven low-spin∕high-spin phase transitions in solids

Biernacki, S. W.; Clerjaud, B.

doi:10.1103/physrevb.72.024406

Cited by 30 publications

(21 citation statements)

References 16 publications

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“…Solid curves are the fittings to the data with the spin-crossover model. tization curves with the spin crossover model of a single ion based on Biernacki and Clerjaud's formulation [29], which is shown to give a qualitative agreement with the experimental results. However, the experimentally obtained y dependence of ∆M does not agree with the model calculation especially when approaching low temperatures.…”

Section: Discussionsupporting

confidence: 65%

“…Last, we note the apparent contrast of the present phase diagram to that of LaCoO 3 and discuss the difference of microscopic origin of those ground states. The spin crossover model used here is based on Biernacki and Clerjaud's formulation [29] where the Boltzmann distribution on a level scheme of a single-ion spin-gap is considered with further modification by mean fields of inter-ion interactions (see the Appendix for details). The calculated B C as a function of T using Eq.…”

Section: Discussionmentioning

confidence: 99%

“…The transition fields as a function of temperature B C (T ) can be obtained by numerically solving Eq. (A5) with the condition of n = 1/2 as [29] T C = ∆ k ln P…”

Section: Discussionmentioning

confidence: 99%

“…Simulated magnetization curves based on the spin-crossover model of a single ion based on Biernacki and Clejaud's formulation[29].…”

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confidence: 99%

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Magnetic-field-induced spin crossover of Y-dopedPr0.7Ca0.3CoO3

et al. 2016

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The family of hole-doped Pr-based perovskite cobaltites, Pr 0.5 Ca 0.5 CoO 3 and (Pr 1−y RE y ) 0.3 Ca 0.7 CoO 3 (where RE is rare earth) has recently been found to exhibit simultaneous metal-insulator, spin-state, and valence transitions. We have investigated magnetic-field-induced phase transitions of (Pr 1−y Y y ) 0.7 Ca 0.3 CoO 3 by means of magnetization measurements at 4.2−100 K up to an ultrahigh magnetic field of 140 T with the chemical pressure varied by y = 0.0625, 0.075, 0.1. The observed magnetic-field-induced transitions were found to occur simultaneously with the metal-insulator transitions up to 100 T. The obtained magnetic field-temperature (B-T ) phase diagram and magnetization curves are well analyzed by a spin-crossover model of a single ion with interion interactions. On the other hand, the chemical pressure dependence of the experimentally obtained magnetization change during the phase transition disagrees with the single ion model when approaching low temperatures. The significant y dependence of the magnetization change at low temperatures may arise from the itinerant magnetism of Co 3+ in the paramagnetic metallic phase, where the chemical pressure enhances the exchange splitting by promoting the double-exchange interaction. The observed B-T phase diagrams of (Pr 1−y Y y ) 0.7 Ca 0.3 CoO 3 are quite contrary to that of LaCoO 3 , indicating that in (Pr 1−y Y y ) 0.7 Ca 0.3 CoO 3 the high-field phase possesses higher entropy than the low-field phase, whereas it is the other way around in LaCoO 3 .

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Section: Discussionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 99%

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Magnetic-field-induced spin crossover of Y-dopedPr0.7Ca0.3CoO3

et al. 2016

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“…7 and 14 and the present work, the ball's radius only with two allowed values, 11,12 or both elastic constants and ball's radii 15,16 ). Quite recently, quantum models based on vibronic (or crystal field) descriptions of the spin-crossover molecules, which include the spin-orbit coupling, have been also proposed 16,17 to describe the thermal properties of SCC.…”

Section: Introductionmentioning

confidence: 74%

Dynamic phase transitions in the one-dimensional spin-phonon coupling model

2013

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An interesting model for spin crossover compounds (SCC) is the so-called spin-phonon coupling model. In this model, the SC units are linked by springs, with elastic constants dependent on their spin states. In the present work, we investigate by means of Monte Carlo Metropolis method, the one-dimensional version of the model at T > 0 K. The relevance of our numerical analysis stands in the possibility of studying this model in the general case, i.e., outside the analytical limits of the mean-field approximation (MFA). First, we investigate a couple of model properties, such as pressure-induced-like effects on thermal hysteresis loops, system size and degeneracy influences on the dynamic phase diagrams. We find a high sensitivity of the hysteresis loops on the system size for small sizes only. Second, we qualitatively compare our results with those analytically obtained in the MFA and determine the limits of the latter. Third, we study the kinetic effects on the dynamic phase diagrams and the critical temperature. We find a slow asymptotic decrease of the critical temperature T c to zero as the kinetics becomes infinitely long. This might be important in the experimental studies of pressure-induced phase transitions for clusters or nanosize SC compounds at low temperatures, as this means that, in practice, there will always be a pseudophase transition, as the measurement time is finite. The transition temperatures are smaller than 0.1 /k B , meaning that is not a question of thermal activation, but it is really the mechanism of spin-phonon coupling that helps the transition from the low-spin to the high-spin level state.

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Ising‐Like Model Hasn't Yet Said Its Last Word: Exact and Mean‐Field Investigations of 2, 3 and 4‐Body Interactions in 1D Ising Chain of Binuclear Spin‐Crossover Solids

Boukheddaden,

Belmouri,

di Scala

2024

ChemPhysChem

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We investigate the static properties of a new class of 1D Ising‐like Hamiltonian for binuclear spin‐crossover materials accounting for two‐, three‐, and four‐body short‐range interactions between binuclear units of spins [[EQUATION]] and [[EQUATION]]. The following 2‐, 3‐ , and 4‐body [[EQUATION]], [[EQUATION]], and [[EQUATION]] terms are considered, in addition to intra‐binuclear interactions, such as effective ligand‐field energy and exchange‐like coupling. An exact treatment is carried out within the frame of the transfer matrix method, leading to a [[EQUATION]] matrix from which, we obtained the thermal evolution of the thermodynamic quantities. Several situations of model parameter values were tested, among which that of competing intra‐ and inter‐molecular interactions, leading to the occurrence of (i) one‐step spin transition, (ii) two‐, three‐, and four‐step transitions, obtained with a reasonable number of parameters. To reproduce first‐order phase transitions, we accounted for inter‐chains interactions, treated in the mean‐field approach. Hysteretic multi‐step transitions, recalling experimental observations, are then achieved. Overall, the present model not only suggests new landscapes of interaction configurations between SCO molecules but also opens new avenues to tackle the complex behaviors often observed in the properties of SCO materials.

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Thermally driven low-spin∕high-spin phase transitions in solids

Cited by 30 publications

References 16 publications

Magnetic-field-induced spin crossover of Y-dopedPr0.7Ca0.3CoO3

Magnetic-field-induced spin crossover of Y-dopedPr0.7Ca0.3CoO3

Dynamic phase transitions in the one-dimensional spin-phonon coupling model

Ising‐Like Model Hasn't Yet Said Its Last Word: Exact and Mean‐Field Investigations of 2, 3 and 4‐Body Interactions in 1D Ising Chain of Binuclear Spin‐Crossover Solids

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