Quantum critical state and electronic structure of two-dimensional Kondo lattice

• Project/Area Number: 26400337
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Keio University
• Principal Investigator: MATOBA Masanori 慶應義塾大学, 理工学部(矢上), 教授 (20229595)
• Co-Investigator(Kenkyū-buntansha): 神原 陽一 慶應義塾大学, 理工学部(矢上), 准教授 (50524055)
• Co-Investigator(Renkei-kenkyūsha): OKADA Satoshi 日本大学, 理工学部, 助教 (50453915)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥4,940,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥1,140,000); Fiscal Year 2016: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2015: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2014: ¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000)
• Keywords: 強磁性量子臨界状態 / 二次元近藤格子系 / 重い電子系

Outline of Final Research Achievements

We have studied Cr-doping effects on the suppressed magnetism and the electronic structure of quasi-2D layered oxypnictide CeFePO with alternating stack of Ce2O2 and Fe2P2 layers to find two quantum critical points (Cr5%, Cr45%) and reveal novel Kondo lattice picture as follows.
The increasing phenomena of the electronic specific heat of CeFePO indicates that the existence of the Kondo singlet was confirmed below 12 K (Kondo temperature). On the other hand, in Cr20%, the appearance of the ferromagnetic transition, the decrease with remarkable electronic thermal capacity and the Kondo breakdown phenomenon are observed below 6 K. Also, the increase of the magnetic phase transition temperature due to applied magnetic field is confirmed, indicating the existence of the ferromagnetic fluctuation in Cr20%. Moreover, from the 57Fe Mossbauer spectrum analysis of Cr50%, it is expected that Fe spin states change into a spin density wave (SDW) below 25 K.

Research Products

• [Journal Article] A Ferromagnetic Quantum Critical Point in Heavy-Fermion Iron Oxypnictide CeFe1-xCrxPO (2015)
  • Author(s): T. Okano, S. Kitao, M. Seto, T. Atou, M. Itoh, M. Matoba, and Y. Kamihara
  • Journal Title: Journal of Applied Physics Volume: 117
  • DOI: 10.1063/1.4916808
  • Peer Reviewed / Acknowledgement Compliant
• [Presentation] Magnetic phases in a 2 dimensional Kondo lattice, CeTMPO (TM = Fe, Ru, Cr, Ni) (2017)
  • Author(s): 神原陽一
  • Organizer: 動的平均場近似計算に関する情報交流会(ワークショップ)
  • Place of Presentation: 東京大学本郷キャンパス（東京都・文京区）
  • Year and Date: 2017-02-16
• [Presentation] 二次元近藤格子系CeFe1-xCrxPOのMossbauer分光及び比熱測定 (2016)
  • Author(s): 谷中慎太郎, 井田和則, 岡野智宏, 北尾真司, 瀬戸誠, 金道浩一, 小濱芳允, 的場正憲, 神原陽一
  • Organizer: 日本磁気学会 第40回学術講演会
  • Place of Presentation: 金沢大学角間キャンパス（石川県・金沢市）
  • Year and Date: 2016-09-08
• [Presentation] 57Fe Mossbauer spectroscopy of heavy fermion CeFe1-xCrxPO (2015)
  • Author(s): Kazunori Ida, Tomohiro Okano, Shinji Kitao, Makoto Seto, Masanori Matoba, Yoichi Kamihara
  • Organizer: International Conference on Electron Spectroscopy and Structure: ICESS-2015
  • Place of Presentation: Charles B Wang Center, Stony Brook University (New York, USA)
  • Year and Date: 2015-09-28
  • Int'l Joint Research
• [Presentation] A Possible Ferromagnetic Quantum Critical Point in Heavy-Fermion Iron Oxypnictide Ce(Fe1-xCrx)PO (2014)
  • Author(s): Tomohiro Okano, Shinji Kitao, Makoto Seto, Toshiyuki Atou, Mitsuru Itoh, Masanori Matoba, Yoichi Kamihara
  • Organizer: The 59th Annual Magnetism and Magnetic Materials (MMM) Conference
  • Place of Presentation: Hilton Hawaiian Village Conference Center (Hawaii, USA)
  • Year and Date: 2014-11-04