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Description:

For cryogenic temperature magnetic refrigeration, we focused on materials containing Eu2+ ions and synthesized sintered composite materials comprising Eu2TiO4 and Eu3Ti2O7. Eu3Ti2O7 and Eu2TiO4 exhibited second-order phase transitions between the paramagnetic and ferromagnetic states at 7 K and 8 K, respectively. The magnetocaloric effect was evaluated from the magnetization and specific heat. It was shown that Eu2+ ions behave similarly to free ions with J=7/2. The maximum magnetic entropy change per unit volume exceeded 0.3 J/cm3K at a magnetic field of 5 T. The Carnot cycle at the hydrogen liquefaction temperature was evaluated using the obtained entropy temperature diagram. It was found that the cooling capacity is several times higher than that of known materials such as GGG, DGAG and GTP. It was also shown that the present composite materials are useful for extending the operating temperature range of the adiabatic demagnetization refrigerator (ADR). These results indicate that Eu2TiO4 and Eu3Ti2O7 composites are promising magnetic refrigerants for cryogenic magnetic refrigeration.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: Magnetocaloric refrigeration, Magnetocaloric effect, Ferromagnetism, Phase transitions, Cooling capacity, Composite materials, Ceramics

Date published: 2025-07-21

Publisher: AIP Publishing

Journal:

• Journal of Applied Physics (ISSN: 00218979) vol. 138 issue. 3 033901

Funding:

• Japan Science and Technology Agency JPMJMI18A3

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1063/5.0278479

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Updated at: 2025-08-19 16:30:28 +0900

Published on MDR: 2025-08-19 16:19:48 +0900