論文

査読有り
2013年7月

Ferromagnetic amorphous oxides in the EuO-TiO2 system studied by the Faraday effect in the visible region and the x-ray magnetic circular dichroism at the Eu M-4,M-5 and L-2,L-3 edges

PHYSICAL REVIEW B
  • Takahiro Kawamoto
  • ,
  • Koji Fujita
  • ,
  • Hirofumi Akamatsu
  • ,
  • Tetsuya Nakamura
  • ,
  • Toyohiko Kinoshita
  • ,
  • Masaichiro Mizumaki
  • ,
  • Naomi Kawamura
  • ,
  • Motohiro Suzuki
  • ,
  • Yoshiro Kususe
  • ,
  • Shunsuke Murai
  • ,
  • Katsuhisa Tanaka

88
2
開始ページ
024405
終了ページ
1
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1103/PhysRevB.88.024405
出版者・発行元
AMER PHYSICAL SOC

Amorphous Eu2TiO4 and EuTiO3 have been studied by a combination of the Faraday effect in the visible region and polarization-dependent x-ray absorption spectroscopy at the Eu M-4,M-5 and L-2,L-3 edges to examine the role of Eu 4f-5d exchange interactions on the ferromagnetic behavior. The bulk-sensitive x-ray absorption spectra (XAS) for Eu L-2,L-3 edges show that most of the europium ions are present as the divalent state in the amorphous Eu2TiO4 and EuTiO3. The Eu M-4,M-5 edge x-ray magnetic circular dichroism (XMCD) signals, measured for the amorphous Eu2TiO4, dramatically increase upon cooling through the Curie temperature (16 K) determined by a superconducting quantum interference device (SQUID) magnetometer. Sum-rule analysis of the XMCD at Eu M-4,M-5 edges measured at 10 K yields a 4f spin magnetic moment of 6.6 mu(B) per Eu2+ ion. These results confirm that the ferromagnetic properties exclusively arise from 4f spins of Eu2+. In addition, for both the amorphous Eu2TiO4 and EuTiO3, the temperature and magnetic-field dependence of Eu L-2,L-3 edge XMCD signals can be scaled with the corresponding magnetization measured by SQUID, indicating that the 5d magnetic polarization of Eu2+ is involved in the process to cause the ferromagnetic interaction between Eu2+ ions. We further discuss the origin of ferromagnetism in the amorphous system on the basis of the energy diagram of Eu 4f and 5d levels deduced from the Faraday effect in the visible region. From the wavelength dependence of Faraday rotation angles of the amorphous EuO-TiO2 system in comparison with those of the divalent Eu chalcogenides as reported previously, it is found that the magnitude of crystal-field splitting of Eu 5d levels in the former is on the same order as that in the latter, which explains an enhanced ferromagnetic exchange interaction between Eu 4f and 5d states.


リンク情報
DOI
https://doi.org/10.1103/PhysRevB.88.024405
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000321669300010&DestApp=WOS_CPL
URL
http://repository.kulib.kyoto-u.ac.jp/dspace/handle/2433/188014
ID情報
  • DOI : 10.1103/PhysRevB.88.024405
  • ISSN : 1098-0121
  • Web of Science ID : WOS:000321669300010

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