Study on Pressure-Induced Valence Transition of Europium Compounds by Thermal Conductivity and Specific Heat Measurements Under Pressure

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K03837
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Shimane University
• Principal Investigator: Nishigori Shijo 島根大学, 学術研究院理工学系, 准教授 (50273917)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: ユーロピウム化合物 / 圧力効果 / 熱伝導率 / 比熱 / 価数転移 / 価数揺動状態 / 熱緩和法

Outline of Final Research Achievements

Using a three-dimensional thermal relaxation method, the pressure dependence of thermal conductivity and specific heat were measured for europium compounds which shows a variety of phenomena arising from valence instability namely valence transitions and fluctuations. To observe the first-order valence transitions correctly, the relaxation method was improved in experimental and analytical aspects. Then the anomalies arising from the valence instability are systematically observed in a wide pressure range. The results provide critical information for understanding the electronic states such as the number of 4f electron levels contributing to the phenomena obtained from the analysis for the magnetic entropy.

Free Research Field

固体物理学

Academic Significance and Societal Importance of the Research Achievements

本研究で発展させた3次元熱緩和法は圧力下での熱特性測定の現状を一変させる画期的なものである。1次相転移の観測および評価が可能になったことは学術的に大きな意味を持つ。その手法を用いて研究対象のユーロピウム化合物の多彩な物性を系統的・網羅的に明らかに出来た。ユーロピウム化合物は特に価数が不安定な物質として注目されており、その物性を理解することは将来的に価数由来の現象を利用した新たなデバイスの開発に繋がると期待できる。