Artículos (Física de la Materia Condensada)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10869

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    Acceso AbiertoPremio Anual Publicación Científica Destacada de la US. Facultad de FísicaArtículo
    A quantitative criterion for determining the order of magnetic phase transitions using the magnetocaloric effect
    (Nature Publishing Group, 2018) Law, Jia Yan; Franco García, Victorino; Moreno Ramírez, Luis Miguel; Conde Amiano, Alejandro; Karpenkov, Dmitriy Y.; Radulov, Iliya; Skokov, Konstantin P.; Gutfleisch, Oliver; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
    The ideal magnetocaloric material would lay at the borderline of a first-order and a second-order phase transition. Hence, it is crucial to unambiguously determine the order of phase transitions for both applied magnetocaloric research as well as the characterization of other phase change materials. Although Ehrenfest provided a conceptually simple definition of the order of a phase transition, the known techniques for its determination based on magnetic measurements either provide erroneous results for specific cases or require extensive data analysis that depends on subjective appreciations of qualitative features of the data. Here we report a quantitative fingerprint of first-order thermomagnetic phase transitions: the exponent n from field dependence of magnetic entropy change presents a maximum of n > 2 only for first-order thermomagnetic phase transitions. This model-independent parameter allows evaluating the order of phase transition without any subjective interpretations, as we show for different types of materials and for the Bean–Rodbell model.
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    Acceso AbiertoPremio Anual Publicación Científica Destacada de la US. Facultad de FísicaArtículo
    Additive manufacturing of magnetocaloric (La,Ce)(Fe,Mn,Si)13–H particles via polymer-based composite filaments
    (Elsevier, 2022-11) Díaz García, Álvaro; Revuelta Losada, Jorge; Moreno Ramírez, Luis Miguel; Law, Jia Yan; Mayer, C.; Franco García, Victorino; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Junta de Andalucía; Air Force Office of Scientific Research
    Additive manufacturing could be an excellent way of shaping magnetocaloric heat exchangers in magnetic refrigerators. However, the metal additive manufacturing techniques present the serious limitation that the melting of a magnetocaloric material can cause its transformation and the loss of functionality. Fused deposition modeling using polymer-based composite filaments is presented as a promising alternative as temperatures are low enough to preserve the magnetocaloric material. To prove this claim, a polymer-based composite filament containing 55 wt% of (La,Ce)(Fe,Mn,Si)13–H magnetocaloric fillers has been manufactured using custom-made polymer capsules as the feedstock for the extrusion. Both adiabatic temperature change and isothermal entropy change have been characterized for the fillers, as-prepared filaments and as-printed parts, indicating that the magnetocaloric material functionality is not altered along the whole process. Printing resolution is comparable to the raw PLA filament.