Magnetic properties of ferromagnetic lanthanoid elements under high pressures

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03379
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Physical properties of metals/Metal-base materials
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: Mito Masaki 九州工業大学, 大学院工学研究院, 教授 (60315108)
• Co-Investigator(Kenkyū-buntansha): 中村 和磨 九州工業大学, 大学院工学研究院, 准教授 (60525236)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: ランタノイド / 希土類金属 / 強磁性 / 高圧力 / 磁気測定

Outline of Final Research Achievements

We have developed a miniature diamond anvll cell (DAC) without any system to adjust clearance between two anvils, which is suitable for magnetic measurements over wide temperature range from liquid helium temperature to room temperature. By using the DAC, we succeeded in measuring ac magnetization for lanthanoid ferromagnetic metals such as Gd, Tb, Dy, and Ho at pressures more than 20 GPa. The cirtical pressures, above which the magnetic orders disappear, were precisely evaluated, and they were compared with the results in previous literatures. In particular, we had to revise the information on critical pressures for Tb and Ho. Consequently we mention that the above critical pressures should not be determined from the data of electrical resistance. A seres of critical pressures was also discussed on the basis of structural phase transitions under pressures.

Free Research Field

固体物性

Academic Significance and Societal Importance of the Research Achievements

“金属強磁性体の磁気秩序が高圧力下でどのようになるか？”は物質科学において重要な関心事である。例えば、鉄は10 GPa超の高圧力下で構造相転移に引きづられる形で強磁性状態が消失し、金属状態が超伝導状態にグレードアップする。ランタノイド系にも６種の強磁性元素が存在するが、高圧力下磁気測定から示唆された磁性状態と電気抵抗測定で主張されことが矛盾していた。今回、高圧力下磁気測定技術を向上させ、Gd-Hoの4元素に対して、信頼のおける磁気測定データを入手し、電位抵抗測定に頼らない形で磁性状態の温度・圧力相図を作成することが出来た。単一元素金属の物性ゆえに真相を明らかにしておく必要があった。