resumo
Maximizing the performance of magnetic refrigerators and thermomagnetic energy harvesters is imperative for their successful implementation and can be done by maximizing their operation frequency. One of the features delimiting the frequency and efficiency of such devices is the phase transition kinetics of their magnetocaloric/thermomagnetic active material. While previous studies have described the magnetic component governing the kinetics of the magnetovolume phase transition in La(Fe,Si)13 giant magnetocaloric materials, a comprehensive description of its structural component has yet to be explored. In this study, in situ synchrotron X-ray diffraction is employed to describe the structural changes upon magnetic field application/removal. Long magnetic field dependent relaxation times up to a few hundred seconds are observed after the driving field is paused. The phase transition is found to be highly asymmetric upon magnetic field cycling due to the different Gibbs energy landscapes and the absence of an energy barrier upon field removal. An exponential relationship is found between the energy barriers and the relaxation times, suggesting the process is governed by a non -thermal activation over an energy barrier process. Such fundamental knowledge on first -order phase transition kinetics suggests pathways for materials optimization and smarter design of magnetic field cycling in real -life devices.
palavras-chave
METAMAGNETIC TRANSITION; MAGNETIC REFRIGERATION; CALORIC MATERIALS; ENTROPY CHANGE; PERFORMANCE; EXPANSION; ALLOYS; LA(FE; STATE
categoria
Materials Science; Physics
autores
Beleza, AA; Pires, B; Almeida, R; Evans, JSO; dos Santos, AM; Frontzek, M; Lovell, E; Beckmann, B; Skokov, K; Gutfleisch, O; Araujo, JP; Abeykoon, AMM; Amaral, JS; Belo, JH
nossos autores
João Cunha de Sequeira Amaral
Investigador Auxiliar
João Silva
Bolseiro de pós-DoutoramentoProjectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
Work partially supported by the projects PTDC/EMETED/3099/2020, UIDP/04968/2020-Programatico (https://doi.org/10.54499/UIDP/04 968/2020), UIDB/04968/2020 (https://doi.org/10.54499/UIDB/04 968/2020"id="intref0030b), LA/P/0095/2020 (https://doi.org/10.5 4499/LA/P/0095/2020), NECL-NORTE-010145-FEDER-022096, CERN/FISTEC/0003/2019 and the bilateral research fund grant SMARTX from Fundacao para a Ciencia e Tecnologia (FCT) and from and the Portuguese Association of Researchers and Student in the UK (PARSUK), Portugal, and within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC) . J.H. Belo also deeply acknowledges Fullbright Portugal for his Fulbright Visiting Scholar grant, and FCT for his contract DL57/2016, with reference DL57/2016,, and DL57/2016/CP1454/CT0013, with reference 10.54499/DL57/2016/CP1454/CT0013, DOI: 10.54499/DL57/2016/CP1454/CT0013. R. Almeida acknowledges FCT for the PhD grant with reference 2022.13354.BD. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. We acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG) within the CRC/TRR 270 (Proj-ect-ID 405553726) .