The local structure and ferromagnetism in Fe-implanted SrTiO₃ single crystals

Journal Article · Mon Jul 07 04:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4886875· OSTI ID:22306177

Chavarha, M. ^[1]; Yiu, Y. M. ^[2]; Sham, T. K.; Goncharova, L. V. ^[1]

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1. Department of Physics and Astronomy, The University of Western Ontario, London ON N6A 5B7 (Canada)
2. Department of Chemistry, The University of Western Ontario, London ON N6A 5B7 (Canada)

We report a connection between the local structure of low-level Fe impurities and vacancies as the cause of ferromagnetic behavior observed in strontium titanate single crystals (STO), which were implanted with Fe and Si ions at different doses then annealed in oxygen. The effects of Fe doping and post-implantation annealing of STO were studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy and Superconducting Quantum Interference Device magnetometry. XANES spectra for Fe and Ti K- and L-edge reveal the changes in the local environment of Fe and Ti following the implantation and annealing steps. The annealing in oxygen atmosphere partially healed implantation damages and changed the oxidation state of the implanted iron from metallic Fe⁰ to Fe²⁺/Fe³⁺ oxide. The STO single crystals were weak ferromagnets prior to implantation. The maximum saturation moment was obtained after our highest implantation dose of 2×10¹⁶ Fe atom/cm², which could be correlated with the metallic Fe⁰ phases in addition to the presence of O/Ti vacancies. After recrystallization annealing, the ferromagnetic response disappears. Iron oxide phases with Fe²⁺ and Fe³⁺ corresponding to this regime were identified and confirmed by calculations using Real Space Multiple Scattering program (FEFF9).

• OSTI ID: 22306177
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 1 Vol. 116; ISSN JAPIAU; ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ABSORPTION SPECTROSCOPY
ANNEALING
FERROMAGNETISM
IMPURITIES
IRON ADDITIONS
IRON OXIDES
MONOCRYSTALS
MULTIPLE SCATTERING
OXYGEN
RECRYSTALLIZATION
SATURATION
SILICON IONS
SPECTRA
SQUID DEVICES
STRONTIUM TITANATES
VACANCIES
X RADIATION
X-RAY SPECTROSCOPY