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Title: Spontaneous formation of suboxidic coordination around Co in ferromagnetic rutile Ti 0.95Co 0.5O 2 film

To evaluate local atomic structures around Co in high temperature diluted ferromagnetic semiconductor Co-doped TiO 2, x-ray fluorescence holography and x-ray absorption fine structure experiments were carried out on rutile paramagnetic Ti 0.99Co 0.01O 2 and ferromagnetic Ti 0.95Co 0.05O 2 films. The Co atoms in the Ti 0.99Co 0.01O 2 simply substituted for Ti sites in the rutile structure, whereas a suboxidic arrangement of CoO 2Ti 4 formed around Co in the Ti 0.95Co 0.05O 2 films. A theoretical investigation based on a series of first-principles calculations indicated the stability of the aggregated suboxidic clusters in the rutile TiO 2, supporting our hypothesis for the formation of suboxidic coordination in the highly Co-doped sample. As a result, the suboxidic coordination may be the source of strong exchange interaction, resulting in the high Curie temperature in Co-doped TiO 2.
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [4] ;  [5] ;  [6] ;  [6] ;  [7] ;  [3]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Tohoku Univ., Sendai (Japan)
  3. The Univ. of Tokyo, Tokyo (Japan)
  4. Hiroshima City Univ., Hiroshima (Japan)
  5. Kumamoto Univ., Kumamoto (Japan)
  6. Japan Atomic Energy Agency, Hyogo (Japan)
  7. JASRI/SPring-8, Hyogo (Japan)
Publication Date:
OSTI Identifier:
1237178
Report Number(s):
BNL-108462-2015-JA
Journal ID: ISSN 0003-6951; APPLAB
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 106; Journal Issue: 22; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; diluted magnetic semiconductor; X-ray fluorescence holography; ferromagnetic materials; crystal structure; X-ray absorption near edge structure; vacancies; exchange interactions