Direct measurements of the conventional and rotational magnetocaloric effects in Gd thick films

abstract

Magnetic refrigeration (MR) offers a sustainable and emission-free solution to the prevalent heat-pumping systems used worldwide. Typically, it utilizes the magnetocaloric effect (MCE) to achieve cooling by changing the external magnetic field intensity. However, an alternative approach involves maintaining a fixed field intensity while manipulating its orientation to induce temperature changes, in an effect known as the rotating MCE (RMCE). While the RMCE has been extensively studied in materials with magnetocrystalline anisotropy, its investigation in polycrystalline magnetocaloric samples with asymmetric shapes has been lacking until recently. In this case, the RMCE is induced by the demagnetizing effect, which becomes more pronounced in high aspect-ratio sample geometries exhibiting different effective demagnetizing factors at different orientations, such as in films. In this work, we characterize the conventional and rotational MCE of 40 mu m-thick gadolinium films through magnetization and direct temperature measurements. The maximum adiabatic temperature change achieved under a 1 T magnetic field was 2.05 K when the film was oriented in plane with the field and 1.25 K when the film was perpendicular to the magnetic field, corresponding to an adiabatic temperature difference of around 0.8 K which may be induced through magnetic field rotation. Additionally, the maximum adiabatic temperature change upon rotation is shown to exhibit a non-monotonous behavior with field intensity, displaying a peak value for field intensities of around 0.8 T. The high aspect ratio of the Gd film has been demonstrated to considerably enhance the intensity of demagnetizing field-based RMCE compared to bulk samples, paving the way for future research in this emerging field of MR cooling.

keywords

MICROWIRES; BEHAVIOR

subject category

Physics

authors

Pereira, CS; Almeida, R; Niehoff, T; Kiefe, R; Fontana, E; Silva, DJ; Gottschall, T; Wosnitza, J; Devillers, T; Dempsey, NM; Amaral, JS; Belo, JH

Groups

G2 - Photonic, Electronic and Magnetic Materials

Projects

Demagnetizing-based magnetocaloric refrigeration (MAGCAL)

Clean and efficient cooling in vaccine transportation using Rotating Magnetocaloric Effect (MAGCCINE )

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

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)

acknowledgements

The work carried out at Universidade do Porto 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) and LISBOA-01-0247-FEDER-039985/POCI-01-0247-FEDER- 039985. This work has received funding from the European Union's Horizon Europe research and innovation programme through the European Innovation Council under the grant agreement No. 101161135 - MAGCCINE. The work carried out at Universidade de Aveiro 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). The fabrication of Gd thick films was developed during the 'HiPerTher-Mag' project (ANR-18-CE05-0019) financed by the French National Research Agency. J H Belo also thanks FCT for the Projects PTDC/FISMAC/31302/2017 and CERN/FISTEC/0003/2019 and FCT for his Contract DL57/2016, with reference SFRH-BPD-87430/2012, 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. We acknowledge the support of the High Magnetic Field Laboratory (HLD) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a member of the European Magnetic Field Laboratory (EMFL), the European Union's Horizon 2020 research and innovation programme through the ISABEL project (No. 871106), the Deutsche Forschungsgemeinschaft (DFG) through SFB 1143, and the Wurzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat (EXC 2147, Project No. 390858490).