Controlling the electronic structure of Co1-xFe2+xO4 thin films through iron doping
The electronic, magnetic and transport properties of iron-doped cobalt ferrite (Co{sub 1-x}Fe{sub 2+x}O{sub 4}) thin films grown epitaxially on MgO (001) substrates are investigated by soft x-ray absorption and photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, superconducting quantum interference device magnetometry, and resistivity measurements. The crystal structure for Co{sub 1-x}Fe{sub 2+x}O{sub 4} is determined to be nearly inverse spinel, with the degree of inversion increasing for increased doping until it becomes fully inverse spinel for Fe{sub 3}O{sub 4}. The doped iron cations have a valency of 2+ and reside solely on octahedral sites, which allows for conduction owing to hopping between Fe{sup 2+} and Fe{sup 3+} octahedral cations. The addition of Fe{sup 2+} cations increases the electron density of states near the Fermi energy, shifting the Fermi level from 0.75 to 0 eV with respect to the top of the valence band, as the doping increases from x = 0.01 to 1. This change in electronic structure results in a change in resistivity by over two orders of magnitude. In contrast, the magnetic properties of CoFe{sub 2}O{sub 4} thin films, characterized by a significantly reduced saturation magnetization compared to the bulk and large magnetic anisotropies, are affected less significantly by doping in the range from 0 to 0.63. These results show that Co{sub 1-x}Fe{sub 2+x}O{sub 4} has tunable electronic properties while maintaining magnetic properties similar to CoFe{sub 2}O{sub 4}.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1020876
- Report Number(s):
- BNL-94713-2011-JA; R&D Project: LS001; KC0401030; TRN: US1103870
- Journal Information:
- Physical Review. B. Condensed Matter and Materials Physics, Vol. 83, Issue 3; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
CATIONS
COBALT
CRYSTAL STRUCTURE
ELECTRON DENSITY
ELECTRONIC STRUCTURE
FERMI LEVEL
FERRITE
IRON
MAGNETIC PROPERTIES
MAGNETIZATION
PHOTOELECTRON SPECTROSCOPY
SATURATION
SPINELS
SQUID DEVICES
SUBSTRATES
THIN FILMS
TRANSPORT
VALENCE
national synchrotron light source