Complete thermodynamic characterization of second-order phase transition magnetocaloric materials exclusively through magnetometry

resumo

To fully assess and improve the performance of near room-temperature magnetic refrigerants, it is crucial to measure and compare their three most relevant thermodynamic properties, and their dependence on temperature (T) and applied magnetic field (H): the isothermal entropy change, Delta Siso(T, H); the adiabatic temperature change, Delta Tad(T, H); and the heat capacity, Cp(T, H). Typically, each thermodynamic property requires its own specialized measurements, which are very time-demanding and can be challenging to setup. In this work, we report a complete thermomagnetic characterization of a benchmark magnetocaloric material, gadolinium, using a single and commercially available SQUID magnetometer. By improving a recently reported method with incremental field ramping steps for measuring temperature through magnetization, we obtained a Delta Tad(T) curve under a 1 T field change with its peak amplitude and maximizing temperature respectively within 2 % and 0.8 % of previously reported values for gadolinium. We were also able to estimate the temperature dependent heat capacity, Cp(T, mu 0H = 0.85T), using the Delta Tad(T) measurements from magnetometry combined with magnetization versus temperature curves at different field values. This estimate of Cp around the transition temperature of gadolinium is within a relative error of 11 % of the experimental and reported values. The reported methodology allows the complete characterization of a second-order magnetocaloric material (Delta Siso(T,H), Delta Tad(T,H), Cp(T,H)) around its Curie temperature using a single and widely available device, which can accelerate studies of different magnetocaloric materials' performance, and approximate their implementation in magnetic refrigeration and/or waste heat energy harvesting industries.

palavras-chave

REFRIGERATION

categoria

Chemistry; Materials Science; Metallurgy & Metallurgical Engineering

autores

Pereira, CS; Almeida, R; Kiefe, R; Amorim, C; Silva, DJ; Amaral, JS; Belo, JH

Grupos

G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G6 - Materiais Virtuais e Inteligência Artificial

Projectos

Demagnetizing-based magnetocaloric refrigeration (MAGCAL)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

agradecimentos

We would like to pay our humble tribute to Vitalij K. Pecharsky whose work opened pathways for an ever-growing scientific and in-dustrial community dedicated to the study of solid-state refrigerants and refrigeration devices and whose life inspired so many young researchers as us.This work was developed within the scope of the following projects financed by EEA grants via the project FBR_OC1_85 and by national funds through the FCT/MCTES (PIDDAC) , UIDB/04968/2020, UIDP/04968/2020, PTDC/EME-TED/3099/2020 (IFIMUP) , LA/P/0006/2020 (CICECO) , LISBOA-01-0247-FEDER-039985/POCI-01-0247-FEDER-039985, LA/P/0037/2020, UIDP/50025/2020, and UIDB/50025/2020 (i3N) . This work was developed 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 thanks FCT for the projects PTDC/FISMAC/31302/2017 and CERN/FISTEC/0003/2019 and for his contract DL57/2016 reference SFRH-BPD-87430/2012. R. Almeida acknowledges FCT for the PhD grant with reference 2022.13354.BD.