Non-equilibrium kinetics of phase transition under adiabatic processes in Fe-based magnetocaloric compounds

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01609
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26010:Metallic material properties-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Fujita Asaya 国立研究開発法人産業技術総合研究所, 材料・化学領域, 上級主任研究員 (10323073)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 磁気熱量効果 / 磁気冷凍 / 熱力学サイクル / 遍歴電子メタ磁性転移 / 非定常現象

Outline of Final Research Achievements

To incorporate a phase-transition kinetics into the classical (ideal gas-based) thermodynamical cycle concept, a new method was developed to observe both the temperature and magnetic state especially during an adiabatic process. Since transient characteristics of the 1st-order phase transition are involved, the adiabatic process as inevitable branches in the thermodynamic cycles accompanies a unique kinetic feature. These results are analyzed based on the phenomenological model of the equation of state (EoS) and it was found that the magnetic state varies by tracing the saddle-point at EoS during the adiabatic process. Also, an in-situ observation for the adiabatic branch in operation of the magnetic refrigeration module indicates that non-steady features of the phase transition were involved in the local fearure of thermodynamic cycles.

Free Research Field

磁性材料工学

Academic Significance and Societal Importance of the Research Achievements

学術面としては、理想気体ベースの古典熱力学（熱サイクル概念）に相転移論を融合させることで、新たな学理基盤が固められる。特に、固体の電子自由度(スピン系)に由来する相転移は、気液相変化現象に比べ未解明な事項も多く、固体電子論的な相転移起源の解明にも寄与する。同時に、工学的側面では、現代社会において急激に重要化している熱マネージメントへの貢献として、低環境負荷/高効率な磁気冷凍技術の進展、さらには社会実装にむけた開発を大きく進展することが可能になる。