Thermodynamics of concomitant charge-transfer, antiferromagnetic, and isostructural transitions in Barocaloric ACu₃Fe₄O₁₂ quadruple perovskites
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| Autoři: | , |
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| Médium: | artículo original |
| Datum vydání: | 2026 |
| Popis: | We develop a minimal Landau theory of the concomitant intersite charge-transfer, antiferromagnetic, and isostructural transitions in the barocaloric quadruple perovskites ACu$_3$Fe$_4$O$_{12}$ (A = La, Pr, Nd, Sm, Eu, Gd, Tb). A non-symmetry-breaking order parameter for the Cu--Fe intersite transfer is taken as primary, with the Fe$^{3+}$ staggered magnetization and the volume strain enslaved to the charge transfer through magnetoelastic and charge-strain couplings. The volume and entropy discontinuities, the thermal expansivities and bulk moduli of the two phases, and the slope of the pressure--temperature phase boundaryare thereby tied to one another through the model couplings. The model yields a pressure-independent transition entropy, so the latent heat isproportional to the transition temperature, accounting for its near-constancy under A-site substitution. Applied to NdCu$_3$Fe$_4$O$_{12}$, the theory reproduces the charge, magnetic, and structural responses across the transition from parameters fixed by experimental data, and resolves the transition entropy into comparablecharge and magnetic contributions by anchoring the magnetic sector on the intrinsic ordering scale of the charge-transferred state. The barocaloric effect is inverse, with a peak isothermal entropy change at $0.5$~GPa of $\simeq 73~{\rm J\,K^{-1}\,kg^{-1}}$, comparable to the quasi-direct determination of $65~{\rm J\,K^{-1}\,kg^{-1}}$. The theory makes explicit the intrinsic thermal expansion of each phase, a contribution omitted in the entropy construction underlying the quasi-direct determination. |
| Země: | Kérwá |
| Instituce: | Universidad de Costa Rica |
| Repositorio: | Kérwá |
| Jazyk: | Inglés |
| OAI Identifier: | oai:kerwa.ucr.ac.cr:10669/104903 |
| On-line přístup: | https://advanced.onlinelibrary.wiley.com/journal/21983844. https://hdl.handle.net/10669/104903 |
| Klíčové slovo: | Thermodynamics Pressure Thermal properties Heat transfer Materials Physical properties |