Local interactions of⁵⁷Fe after electron capture of⁵⁷Co implanted in alpha-Al₂O₃and in alpha-Fe₂O₃

Abstract

-Al2 O3 and -Fe2 O3 were implanted with 57 Co at room temperature. -Al2 O3 showed complex Mössbauer spectra indicating paramagnetic hyperfine splitting for high-spin Fe3+ and electric quadrupole-split spectra for Fe2+ ions. In canted antiferromagnet -Fe2 O3 , the implanted Co atoms were positioned substitutionally in Fe2 O3 and at higher doses in Fe3 O4 and in Fe1-x O. In the different phases, the ions were in Fe2+ and/or in Fe3+ states after the electron capture of 57 Co; no after-effects were observed. The results suggest that the phases are formed during fast cooling and crystallization of the oxide from the high-temperature state of the thermal spike.

Mössbauer spectroscopy of 57Fe in α-Al2O3 following implantation of 57Mn*

“…A similar (if not identical) single line component (δ = 0.54-0.55 mm/s) was observed in the 57 Co data of Dézsi et al [9]. In the electron capture of 57 Co, only a minor (<1 eV) recoil is imparted on the 57 Fe daughter nuclei, so it seems unlikely that S1 originates from a recoil produced 57 Fe.…”

“…1, but with the central part removed and the vertical scale expanded to reveal the structure in the outer flanks the central part of the spectra contains a single line (S1) with room temperature parameters similar to those observed by Dézsi et al [9]. Below room temperature, this line shows broadening and disappears from the spectra at T > 500 K. At T > 600 K, the central part of the spectra is dominated by a quadrupole doublet (D1).…”

“…Together with the data from [8] and [9], we can extend the range in implantation fluence, where the average valence state of Fe is determined. The results are shown in Fig.…”

“…They observed a gradual change from an Fe 2+ dominated spectrum to a spectrum dominated by uncharged iron. Dézsi et al [9] performed 80 keV 57 Co implantations to fluences of (1-3) × 10 14 57 Co/cm 2 and observed Fe in the 3+ and 2+ charge states, together with a single line of unknown origin.…”

Anticoincidence measurement of 57Fe Mössbauer spectra obtained after 57Mn implantation: application to Fe in α-Al2O3

“…The electron density and the electric field gradient in various clusters of Fe@Al n O m were calculated by the ORCA program. The obtained [11]. The temperature dependence of the relative intensities in this study suggests that the lattice defects gradually recover with an increase of temperature.…”