Strong correlation effects of the Re 5d electrons on the metal-insulator transition in Ca2FeReO6

H. Iwasawa, T. Saitoh, Y. Yamashita, D. Ishii, H. Kato, N. Hamada, Y. Tokura, and D. D. Sarma
Phys. Rev. B 71, 075106 – Published 8 February 2005

Abstract

We have investigated the electronic structure of polycrystalline Ca2FeReO6 using photoemission spectroscopy and band-structure calculations within the local-density approximation+U (LDA+U) scheme. In valence-band photoemission spectra, a double-peak structure which is characteristic of the metallic double-perovskite series has been observed near the Fermi level (EF), although it is less distinct compared to the Sr2FeMoO6 case. The leading near-EF structure has a very weak spectral weight at EF above the metal-insulator transition (MIT) temperature TMI of 140K, and it loses the EF weight below TMI, forming a small energy gap. To reproduce this small energy gap in the calculation, we require a very large effective U (Ueff) for Re (4eV) in addition to a relatively large Ueff for Fe (4eV). Although the most of the experimental features can be interpreted with the help of the band theory, the overall agreement between the theory and experiment was not satisfactory. We demonstrate that the effective transfer integral between Fe and Re is actually smaller than that between Fe and Mo in Ca2FeMoO6, which can explain both the MIT and very high ferrimagnetic transition temperature.

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  • Received 11 August 2004

DOI:https://doi.org/10.1103/PhysRevB.71.075106

©2005 American Physical Society

Authors & Affiliations

H. Iwasawa, T. Saitoh*, Y. Yamashita, and D. Ishii

  • Department of Applied Physics, Tokyo University of Science, Shinjuku-ku, Tokyo 162-8601, Japan

H. Kato

  • Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan

N. Hamada

  • Department of Physics, Tokyo University of Science, Chiba 278-8510, Japan

Y. Tokura

  • Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan, Spin Superstructure Project, ERATO, Japan Science and Technology Corporation (JST), Tsukuba 305-8562, Japan, and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan

D. D. Sarma

  • Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India

  • *Corresponding author. Electronic address: t-saitoh@rs.kagu.tus.ac.jp
  • Present address: Fuji Electric Advanced Technology Co. Ltd., Hino 191-8502, Japan.
  • Also at Jawaharlal Nehru Centre for Advanced Scientific Research, India.

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Issue

Vol. 71, Iss. 7 — 15 February 2005

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