Searching for preferential orientations of magnetic fossils in rocks: possible clues to paleomagnetism and bacterial ecology

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K18744
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 17:Earth and planetary science and related fields
• Research Institution: Kanazawa University
• Principal Investigator: USUI Yoichi 金沢大学, 地球社会基盤学系, 准教授 (20609862)
• Co-Investigator(Kenkyū-buntansha): 加藤 真悟 国立研究開発法人理化学研究所, バイオリソース研究センター, 上級研究員 (40554548)
• Project Period (FY): 2022-06-30 – 2024-03-31
• Keywords: 磁性細菌 / 強磁性共鳴 / 異方性 / 地球磁場

Outline of Final Research Achievements

Bacteria called magnetotactic bacteria, which are often found in sediments, synthesize long chains of magnetite (natural magnets) in their bodies. These bacteria should align along the direction of the Earth's magnetic field, but there has been no direct detection of this alignment. In this study, we investigated a new method of detecting the alignment of magnetic bacteria by the absorption of microwaves by magnetite. Various fixtures were made to change the direction of the magnetic field applied to the sample, and measurements were performed. Currently, the expected direction-dependent signal and noise level are comparable, and no clear detection has been achieved.

Free Research Field

古地磁気学

Academic Significance and Societal Importance of the Research Achievements

既存のマイクロ波吸収測定装置内に収まるような治具の作成の試行錯誤を行った。特に、水分によるマイクロ波吸収を軽減することと、試料準備時の磁場方位と測定時の方位との関係をコントロールすることが課題であったが、その問題はおおむね解決している。継続的測定によって、この手法による配列検出の限界値を明らかにし、上記の試行錯誤と合わせて報告することで、さらなる研究の展開に貢献できると考えている。