Investigation into giant magnetoresistance in molecular conductor by resonant x-ray scattering

2015 Fiscal Year Final Research Report

• Project/Area Number: 24340084
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Osaka University
• Principal Investigator: Hanasaki Noriaki 大阪大学, 理学(系)研究科(研究院), 教授 (70292761)
• Co-Investigator(Kenkyū-buntansha): NOGAMI Yoshio 岡山大学, 大学院自然科学研究科, 教授 (10202251)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: 強相関電子系 / 巨大磁気抵抗 / 電荷秩序 / 分子性伝導体 / フタロシアニン

Outline of Final Research Achievements

In this study, we investigated the mechanism of the giant magnetoresistance observed in the phthalocyanine (Pc) molecular conductor. We found that the x-ray absorption spectra are sensiive to the Pc molecular charge just above the Fe K edge, and tried to detect the charge order of the pi conduction electron by measuring the resonant x-ray scattering. We found that the intramolecular interaction between the pi conduction electron and the d local moment is a ferromagnetic one, which is larger than 500K. This indicates that the magnetic order of the local moments controls the stability of the charge order in the pi conduction electron system. We reduced the density of the local moments by substituting with the Co atom, and observed the giant magnetoresistance in the low spin density. This giant magnetoresistance cannot be explained by the conventional model such as the manganese oxides, indicating the nontrivial electronic state.

Free Research Field

物性物理学