2023 Fiscal Year Final Research Report

Microscopic and systematic investigations for realization of ferromagnetic quantum critical point at zero field

Research Project

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Project/Area Number	21K03446
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	Kobe University
Principal Investigator	Kotegawa Hisashi 神戸大学, 理学研究科, 准教授 (30372684)
Co-Investigator(Kenkyū-buntansha)	松岡英一神戸大学, 理学研究科, 准教授 (20400228)
Project Period (FY)	2021-04-01 – 2024-03-31
Keywords	強磁性体 / 量子臨界点 / 量子相転移 / 異常ホール効果 / 反強磁性
Outline of Final Research Achievements	It has been considered that ferromagnetic quantum critical point (QCP) cannot be realized without an external magnetic field, but NQR measurement for CeRh6Ge4 revealed that a second-order phase transition is maintained even under pressure near the QCP. For CeZn, our measurements show that a new phase like antiferromagnetic phase suddenly appears near the QCP. This impresses the instability of the ferromagnetic QCP and show the variety of the behavior near the ferromagnetic CQCP. We also revealed a magnetic structure of NbMnP. It showed an anomalous Hall effect, which is a ferromagnetic response, even in the antiferromagnetic structure.
Free Research Field	固体物理
Academic Significance and Societal Importance of the Research Achievements	強磁性量子臨界点はゼロ磁場では実現しないとされており、固体物理の中で一種の普遍的性質の一つと考えるのが通説であった。しかし、本研究を通して物質によっては強磁性量子臨界点を持ち得ることが明らかになりつつあり、物質の多様性を強く印象付ける成果を得ていることが学術的な意義である。また、本研究を通して異常ホール効果などの強磁性的応答を示す反強磁性的物質も見つかっている。本系は将来的に反強磁性体を用いたメモリは熱電変換材料への応用に結びつく可能性がある。