Alloying by high dose ion implantation of iron into magnesium and aluminium

Alloys of the systems Fe–Al (mixable over the whole concentration range) and Fe–Mg (insoluble with each other) were produced by implantation of Fe ions into Al and Mg, respectively. The implantation energy was 200 keV and the ion doses ranged from 1 × 10₁₄ to 9 × 10₁₇cm^-2The obtained implantation profiles were determined by Auger electron spectroscopy depth profiling. Maximum iron concentrations reached were up to 60 at.% for implantation into Al and 94 at.% for implantation into Mg. Phase analysis of the implanted layers was performed by conversion electron Mössbauer spectroscopy and X‐ray diffraction. For implantation into Mg, two different kinds of Mössbauer spectra were obtained: at low doses paramagnetic doublets indicating at least two different iron sites and at high doses a dominant ferromagnetic six‐line‐pattern with a small paramagnetic fraction. The X‐ray diffraction pattern concluded that in the latter case a dilated αiron lattice is formed. For implantation into Al, the Mössbauer spectra were doublet structures very similar to those obtained at amorphous Fe–Al alloys produced by rapid quenching methods. They also indicated at least two different main iron environments. For the highest implanted sample a ferromagnetic six‐line‐pattern with magnetic field values close to those of Fe₃Al appeared.     

DCEMS of neon implantation in yttrium iron garnet

⁵⁷Fe-enriched, epitaxial Y₃Fe₅O₁₂ films have been implanted with 50 keV and 100 keV neon ions with a dose of 4·10¹⁴Ne⁺/cm². Depth-selective conversion electron Mössbauer spectroscopy has been performed at 300 K and 40 K. The results show that the 50 keV-implanted sample can be interpreted as an amorphous layer on top of an almost unperturbed YIG layer. In the 100 keV-implanted film a buried amorphous layer is observed.     

Lattice site location and electronic structure of Te in GaAs

High purity <100> wafers of GaAs were implanted with radioactive^129mTe and stable¹²⁸Te at 110 keV to total doses of 2×10¹⁴ and 2×10¹⁵ Te/cm² respectively and studied with RBS/ channeling and Mössbauer spectroscopy on the 27.8 keV level of¹²⁹I. After implantation and/or annealing at temperatures between 200–300°C the Mössbauer spectra are dominated by a single line. Channeling reveals an appreciable residual damage in the host lattice, but also points to a substitutional position of the Te atoms. After annealing above ≌500°C, where nearly complete lattice damage recovery is obtained, the Te atoms become defect-associated. The results clearly point to the formation of Te_As?V_Ga complexes.     

Phase analysis in α-Fe after high-dose Si ion implantation by depth-selective conversion-electron Mössbauer spectroscopy (DCEMS)

Si⁺ ions of 50 keV in energy were implanted into α-Fe (95% ⁵⁷Fe) with a nominal dose of 5 × 10¹⁷ cm^?2 at 350°C. The depth distribution of the Fe-Si phases formed by ion implantation after annealing at 300 and 400°C for 1 h was studied quantitatively by depth-selective conversion-electron Mössbauer spectroscopy (DCEMS). Ordered Fe₃Si and ε-FeSi was observed.     

Ion beam induced phase transformation in Fe–Mn bilayers: a Mössbauer study

Ion‐beam mixing of Fe–Mn bilayers induced by 100 keV krypton ions in the dose range (0.1-15)×10¹⁵ ions/cm²has been studied by means of conversion electron Mössbauer spectroscopy and X‐ray diffraction. The results indicate that a dose of about 1 ×10¹⁵ Kr⁺/cm² is sufficient to induce an appreciable mixing between the two atomic species. The α-Fe(Mn)solid solution presents a maximum at this dose, while at higher doses also the ? and γFe–Mn phases are formed in an appreciable amount. Heating of irradiated samples evidences the metastable character of ? phase and favours the growth of the terminal structures γ-Fe(Mn) and α-Mn(Fe) of the Fe–Mn equilibrium phase diagram.     

Electric field gradients at Os nuclei in the hexagonal transition metals Os and Re

The electric field gradient eq at Os nuclei in Os and Re single crystals has been determined by Mössbauer transmission experiments with the 137 keV resonance in ¹⁸⁶Os as -4.5 (3) × 10¹⁷ V/cm² and - 3.8 (3) × 10¹⁷ V/cm², respectively.     

A cems study of119Sn ion-implanted into Ni

Conversion electron Mössbauer spectroscopy (CEMS) was applied to study the behaviour of¹¹⁹Sn atoms implanted into Ni at the accelerating energy of 100–400KeV and doses of 5×10¹⁵–5×10¹⁶ ions/cm² at room temperature. All CEMS spectra were measured at room temperature and successfully analyzed by two components. The energy and dose dependence of CEMS spectra were well explained by the depth distribution of¹¹⁹Sn atoms.     

Magnetic properties of H+ implanted bubble garnet films by means of depth selective conversion electron Mössbauer spectroscopy

Bubble garnet films before and after 50 keV H⁺ implantation have been studied by means of DCEMS. The spintilt angle of the films as grown after etching off 1000 å was measured to be 30±2? relative to the surface normal at the top of the surface. The doses of implanted H⁺ ions were 2, 4 and 8×10¹⁶ ions/cm². Mössbauer spectra were measured after successive etching of the implanted layer. The magnetic hyperfine field was obtained as a function of depth. The implanted hydrogen distribution was also measured by the¹H(¹⁵N, αγ)¹²C reaction.     

Features of the radioactive decay of Mössbauer isotopes in the presence of an intrinsic gamma-radiation field

A limit for the concentration of radioactive nuclei (3 × 10¹⁴ 1/cm³) of the Mössbauer emitters ^119m Sn and ^125m Te below which the earlier demonstrated effect of the collective nuclear decay vanishes is experimentally found in the framework of a study aimed at the control of the decay of nuclear levels. A general theoretical concept of the phenomenon is presented. Based on this concept, the parameters of the nonexponential decay are numerically estimated. The notion of the width of the Mössbauer γ photon is introduced.     

Structural Transformations in Fe/Zr Bi- and Multilayers Induced by Ion-Beam Mixing

The Ar-ion-beam mixing of Fe/Zr bi- and multilayers is studied by conversion electron Mössbauer spectroscopy as a function of ion dose ranging from 1×10¹⁴ to 1×10¹⁷ at./cm². The mixing leads to amorphization of the Fe/Zr system. It was shown that the mixing process in bilayers depends strongly on the thickness of the Zr substrate. The amorphization is much more effective and occurs at lower ion doses in multilayers as compared to corresponding bilayers.     

Emission Mössbauer spectroscopy study of fluence dependence of paramagnetic relaxation in Mn/Fe implanted ZnO

Emission Mössbauer Spectroscopy following the implantation of radioactive precursor isotope ⁵⁷Mn⁺ (T _1/2= 1.5 min) into ZnO single crystals at ISOLDE/CERN shows that a large fraction of ⁵⁷Fe atoms produced in the ⁵⁷Mn beta decay is created as paramagnetic Fe³⁺ with relatively long spin-lattice relaxation times. Here we report on ZnO pre-implanted with ⁵⁶Fe to fluences of 2×10¹³, 5×10 ¹³ and 8 × 10¹³ ions/cm² in order to investigate the dependence of the paramagnetic relaxation rate of Fe³⁺ on fluence. The spectra are dominated by magnetic features displaying paramagnetic relaxation effects. The extracted spin-lattice relaxation rates show a slight increase with increasing ion fluence at corresponding temperatures and the area fraction of Fe³⁺ at room temperature reaches a maximum contribution of 80(3)% in the studied fluence range.     

Mössbauer characteristics of glauconitisation

Using 50 MeV Li^3?+? ion irradiation, the change induced in polycrystalline ferrites Li_0.5(1?+?x)Ti _x Al_0.1Fe_2.4???1.5x O₄ (x = 0.0 to 0.3, step–0.1)[LTAF] and Li_0.5(1?+?x)Ti _x Cr_0.1Fe_2.4???1.5x O₄ (x = 0.0 to 0.3, step–0.1; LTCF) in the electronic stopping power regime is studied. Both the systems were irradiated with the same fluence of 5 × 10¹³ ions/cm². The modifications of the structural and magnetic properties are studied by means of X-ray diffraction (XRD), magnetization, ⁵⁷Fe Mössbauer spectroscopy and low field a. c. susceptibility. The contrast in the role of Ti^4?+? in the presence of Al^3?+? and Cr^3?+? causing the formation of paramagnetic centres through Swift Heavy Ion Irradiation (SHII) induced cation rearrangement has been revealed through the comparative Mössbauer signatures of both the systems. The hyperfine interaction parameters deduced through Mössbauer spectra are also discussed before and after irradiation. The observed reduction in the saturation magnetic moment and Curie temperature after irradiation supports the partial formation of paramagnetic centres and rearrangement of cations in the lattice.     

Changes in the iron atomic state in the near-surface layers of zirconium alloys irradiated by Ar<Superscript>+</Superscript> ions

The effect of irradiation by an argon ion beam with a broad energy spectrum and an average energy of 10 keV in a dose range of (1?10) × 10¹⁸ ion cm^?2 on the state of iron atoms in the near-surface layers of zirconium alloys Э635, NSF, and Zry-2 was studied by means of conversion electron Mössbauer spectroscopy (CEMS).     

Calibration of the isomer shift of119Sn from internal conversion measurement

Radioactive¹¹⁹Sb was implanted into 6 different host matrices, Y, Β-Sn, Pt, Au, Pb and CaSnO₃, and internal-conversion and Mössbauer spectra were measured for the same samples. The isomer-shift calibration constant of the Mössbauer transition of¹¹⁹Sn was derived as δR/R=(0.87±0.25)×10^?4 for R=1.2×A^1/3 fm or, δ〈r²〉=(3.6±1.0)×10^?3 fm².     

Thermal evolution of high dose iron implanted sintered alumina

Sintered plates of alumina have been implanted at room temperature with 110 keV⁵⁷Fe⁺ at a dose of 1.2×10¹⁷ ions.cm^?2. The analysis of the Conversion Electron Mössbauer Spectrum indicated that implantation introduces iron in alumina in three charge state: Fe²⁺ (two components), Fe⁴⁺ and Fe⁰ (metallic clusters). The evolution of the iron depth distribution during annealings in oxiding or in neutral atmosphere has been followed using the Rutherford backscattering spectroscopy. Up to 800°C the profile as well as the charge states of iron evolve very slowly. A drastic change occurs' for annealing temperature around 1000°C. The total amount of iron is distributed among α-Fe₂O₃ and α-(Fe_1?x Al _x )₂O₃ precipitates. Some scanning electron micrographs have allowed to locate these precipitates. For highest temperature anneals, up to 1600°C, only substitutional iron remain.     

Observation of spin-lattice relaxations of dilute Fe3+ in MgO by Mössbauer spectroscopy

We present a method to describe the temperature dependence of emission Mössbauer spectra showing slow spin-lattice relaxations of Fe^3?+? in MgO single crystals, obtained after implantation of ⁵⁷Mn at ISOLDE/CERN. The analysis is based on the Blume-Tjon model for the line-shape of relaxing paramagnetic sextets with the spin relaxation rate, τ ^???1 as a parameter. The temperature dependent spin relaxation rate of Fe^3?+? in MgO is found to increase to ~10⁸ s^???1 at 647 K by assuming a relaxation rate of τ ^???1?< 10⁶ s^???1 at 77 K. The results are in accordance with those obtained by electron paramagnetic resonance spectroscopy demonstrating the possibility of retrieving spin-lattice relaxation rates of dilute Fe^3?+? from emission Mössbauer spectroscopy of Mn/Fe-implanted oxides.     

Annealing behaviour of iron implanted zirconia

A zirconia film was implanted at room temperature with 100 keV⁵⁷Fe⁺ to a fluence of 8×10¹⁶ ions/cm². The analysis of the Conversion Electron Mössbauer spectra shows that iron is distributed among different charge states: Fe⁰ (in a form of small and large metallic iron aggregates) Fe²⁺ and Fe⁴⁺. The evolution of the iron depth profile deduced from Rutherford backscattering measurements as well as the change in the charge states of iron as a function of annealing under argon atmosphere are presented.     

Mössbauer study of the microscopic surrounding of co atoms implanted in si and ge below the full amorphization limit

Mössbauer spectroscopy on ⁵⁷Co implanted into Si and Ge at doses between 10¹¹ and 10¹⁵ atoms/cm² supports the single track amorphization model. Calculations based on linear cascade theory do not give quantitative agreement with the experiment.     

钴离子注入对二氧化钛晶体的结构和光学性能的影响

采用离子注入法制备了钴离子掺杂的金红石相TiO₂样品;离子注入能量、注量分别为40 keV(1×10¹⁶cm^-2),80 keV(5×10¹⁵,1×10¹⁶,5×10¹⁶,1×10¹⁷cm^-2),120 keV(1×10¹⁶cm^-2). 通过XRD,XPS和UV-Vis等手段对掺杂前后样品的结构和光学性能进行了表征,分析了掺杂元素在金红石TiO₂中的存在形式. XRD测试表明随着注入能量的增加晶体的损伤程度增加. UV-Vis测试表明掺杂后所有样品在可见光区的吸收增强; 并且随着注量的增加,注量为5×10¹⁵cm^-2到5×10¹⁶cm^-2范围内注入样品的光学带隙逐渐变小. 关键词： 钴 二氧化钛 离子注入 掺杂