Mössbauer spectroscopy of exchangeable ions

In this paper Mössbauer spectroscopy is used to study anion exchange processes. In β-FeOOH the effect of the exchangeable ions OH^?, Cl^? and F^? on lattice iron is studied. For the anion exchangers ZrO₂ and the resins amberlite IRA 400, Dowex MSA-1 and Dowex MWA-1, Fe(II)- and Fe(III) hexacyanides are used as Mössbauer probes. The confirmation of a third doublet in F^?-exchanged β-FeOOH and the perturbation of redox equilibrium in the other exchangers are the main observations.     

Cobalt-silicide structures studied by Mössbauer spectroscopy

Mössbauer spectroscopy of cobalt-silicides proved the existence of three stoichiometric phases: CoSi₂, CoSi and Co₂Si. The values of the hyperfine parameters indicated covalent bonds between Co and Si in all phases and could be understood on the basis of their crystallographic structure and of theoretical predictions for the electronic structure. For CoSi₂, anomalous spectra were obtained, the origin of which was not clear. The different spectra of the cobalt-silicides permit the prospective use of Mössbauer spectroscopy for the study of formation and structure of Co/silicide/silicon interfaces.     

Sensitivity of <Superscript>57</Superscript>Fe emission Mössbauer spectroscopy to Ar and C induced defects in ZnO

Emission Mössbauer Spectroscopy (eMS) measurements, following low fluence (<10¹² cm^?2) implantation of ⁵⁷Mn (t _1/2 = 1.5 min.) into ZnO single crystals pre-implanted with Ar and C ions, has been utilized to test the sensitivity of the ⁵⁷Fe eMS technique to the different types of defects generated by the different ion species. The dominant feature of the Mössbauer spectrum of the Ar implanted ZnO sample was a magnetic hyperfine field distribution component, attributed to paramagnetic Fe³⁺, while that of the C implanted sample was a doublet attributed to substitutional Fe²⁺ forming a complex with the C dopant ions in the 2^? state at O vacancies. Magnetization measurements on the two samples, on the other hand, yield practically identical m(H) curves. The distinctly different eMS spectra of the two samples display the sensitivity of the probe nucleus to the defects produced by the different ion species.     

Mössbauer study of the amorphization process in diamond

⁵⁷Co is implanted at different doses in diamond and graphite. The⁵⁷Fe Mössbauer spectrum is studied under various heat treatments. It is found that, in contrast with the measurements of⁵⁷Co implanted Si and Ge, the damage production in diamond can not be described by a direct amorphization model. At lower implantation doses, the defects in diamond can be partly annealed, when the sample is heated after or during implantation. At higher implantation doses graphitization occurs.     

Magnetism in iron implanted oxides: a status report

Emission Mössbauer spectroscopy on ⁵⁷Fe fed by ⁵⁷Mn ions implanted in the metal oxides ZnO, MgO and Al₂O₃ has been performed. The implanted ions occupy different lattice sites and charge states. A magnetic part of the spectra in each oxide can be assigned to Fe^3?+? ions in a paramagnetic state with unusually long relaxation time observable to temperatures up to several hundreds Kelvin. Earlier expectations that the magnetic spectra could correspond to an ordered magnetic state could not be confirmed. A clear decision for paramagnetism and against an ordered magnetic state was achieved by applying a strong magnetic field of 0.6 Tesla. The relaxation times deduced were compared to spin–lattice relaxation times from electron paramagnetic resonance (EPR).     

Mössbauer study of Fe in GaAs following 57Mn + implantation

The metastable 2S state in muonic hydrogen is particularily interesting because a measurement of the Lamb shift could reduce the uncertainty in the proton charge radius by an order of magnitude. The most important prerequisite for such a measurement is a sufficiently large population and lifetime of the 2S state. We have determined the long-lived and short-lived 2S population, the deexcitation mechanisms and lifetimes, and the cascade time in μp.     

Mössbauer spectroscopy investigation of the persistent photoionization of the DX-center in129mTe-implanted GaAs

Persistent photoionization of the DX-center in GaAs implanted with^129mTe isotopes is observed with Mössbauer spectroscopy. The time constant of the relaxation from the donor site to the DX-center defect site, after the illumination is stopped, is measured as a function of temperature. A small energy barrier for capture (1 meV) is derived from these measurements.     

Possible cage motion of interstitial Fe in α-Al 2 O 3

In addition to spectral components due to Fe^2?+? and Fe^3?+?, a single line is observed in emission Mössbauer spectra following low fluence (<10¹⁵ cm^???2) implantation of ⁵⁷Fe*, ⁵⁷Mn and ⁵⁷Co in α-Al₂O₃. For the ⁵⁷Co and ⁵⁷Mn implantations, the intensity of the single line is found to depend on the emission angle relative to the crystal symmetry axis. This angular dependence can be explained by a non-isotropic f-factor and/or motion of the Fe ion between sites in an interstitial cage. It is argued that interstitial cage motion is a more likely explanation, as this can account for the lack of quadrupole splitting of the line.