Radiogenic Sn defects in ion-implanted CdTe

Radioactive^119mCd⁺ and¹¹⁹In⁺ ions have been implanted into CdTe single crystals at temperatures between 50–300K. Radiogenic defects formed with the daughter¹¹⁹Sn have been investigated by Mössbauer spectroscopy of the emitted 24 keV γ radiation. All Mössbauer spectra could be analysed consistently with three lines. These are proposed to be due to substitutional Sn on Cd sites in two different charge states and to Sn-vacancy complexes. The corresponding In-parent vacancy complexes anneal at 120K and above 300K.     

Tin-doped spinel-related oxides of composition M3O4 (M = Mn, Fe, Co)

Tin-doped compounds of spinel-related M₃O₄ (M = Fe, Mn, Co) have been studied by ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectroscopy in the temperature range of 20–600 K. The ¹¹⁹Sn Mössbauer spectra recorded down to 20 K from the non-iron-containing compounds of Co₃O₄ and Mn₃O₄ contained only doublets showing no transfer of magnetic properties from cobalt or manganese to the dopant tin ions. In contrast, the tin-doped-(FeCo)₃O₄ and (FeMn)₃O₄ gave ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectra, which showed magnetic hyperfine interactions. The Curie temperature has been estimated for the former sample.     

Internal oxidation of 5sp impurities in noble metals

The internal oxidation of ion-implanted radioactive¹¹⁹In,¹¹⁹Cd, and¹¹⁹Sb in high-purity (5N) copper, silver, and gold single crystals has been investigated. The formation of the impurity-oxygen defect structures was monitored by Mössbauer emission spectroscopy on the 24 keV-radiation from the daughter¹¹⁹Sn after the-decay of the implanted radioactive isotopes. Molecule-like complexes are formed consisting of the implanted impurity and several oxygen atoms. The various Mössbauer parameters (isomer shift, quadrupole splitting, and Debye temperature) enable a distinction between different Sn-IV and Sn-II complexes, as well as between substitutional and vacancy-associated Sn atoms, which result from the ion implantations. The evolution of oxygen complexes with temperature during isochronal annealing was studied in the temperature range 300–1000 K. The formation (around 500 K) and the disintegration (around 900 K) of the complexes, in' silver in particular, are explained on the basis of diffusion properties of oxygen. A comparison of results from oxidations due to either thermal diffusion of oxygen or due to recoil implantations from a surface-oxide layer indicates that Sn-IV complexes are invariably formed in the first case, whereas in the latter case, a mixture of Sn-IV and Sn-II complexes is formed. Relations of the present results to similar results from PAC measurements on¹¹¹Cd in silver and from Mössbauer experiments on AgSn alloys are discussed.     

Internal oxidation of sp-Impurities in silver studied by119Sn Mössbauer spectroscopy

The internal oxidation of the ion-implanted radioactive precursors¹¹⁹Cd and¹¹⁹Sb to the Mössbauer isotope¹¹⁹Sn in silver has been investigated. The oxidation is monitored by the intensity of a line in the Mössbauer spectra, which is characteristic of SnO₂ (δ=(0–0.23)mm/s relative to CaSnO₃, ΔEQ ≈ 0.5 mm/s, ? ≈ 220 K). This line is attributed to an internal oxidation of the implanted impurities by interstitially diffusing oxygen pairs. The formation and annealing kinetics of the impurity-oxygen complexes are interpreted in terms of the diffusion coefficients of oxygen and the sp-impurities in silver, respectively, and the reactivity between them. Comparison is made to Mössbauer experiments on SnAg alloys and to PAC measurements on¹¹¹cd in silver.     

119Sn Mössbauer study of the implantation behaviour of119In,119Sn,119mSn,119Sb and119mTe ions in SiC

The implantation behaviour of stable¹¹⁹Sn⁺ ions and radioactive¹¹⁹In⁺,^119mSn⁺,¹¹⁹Sb⁺ and^119mTe⁺ ions in SiC has been investigated by, respectively, conversion-electron Mössbauer spectroscopy on the 24 keV transition of¹¹⁹Sn, and by Mössbauer emission spectroscopy on the 24 keV radiation emitted by the¹¹⁹Sn daughter after the decays of the radioactive isotopes. The Mössbauer spectra could be decomposed in most cases into two groups of lines, one originating from¹¹⁹Sn atoms on substitutional Si sites, the other from various Sn-vacancy complexes distinguished by their Mössbauer parameters. Annealing experiments reveal a strong dependence of the structure of the defects and the formation and annealing kinetics on the chemical nature of the impurities. Defects formed in 297 K implantations with^119mSn and¹¹⁹Sb anneal above 500 C, resulting in a preferential location of the impurities on substitutional Si sites, whereas^119mTe atoms are efficient defect-trapping centres and no stable, substitutional fraction is observed on either lattice site. Possible structures for the Sn-vacancy complexes are discussed and comparison is made to similar defect complexes in group IV and in III–V semiconductors.     

A 57Fe and 119Sn Mössbauer study of BaFe4Sn2O11

The Mössbauer spectrum of BaFe₄Sn₂O₁₁ has been recorded for both ⁵⁷Fe and ¹¹⁹Sn isotopes at a variety of temperatures. In the paramagnetic state the ⁵⁷Fe spectra are interpreted in terms of three iron environments. Magnetic ordering begins at 77 K and is virtually complete by 4.2 K to give an average magnetic hyperfine field of 504 kG. The ¹¹⁹Sn spectra also reflect the magnetic ordering and a magnetic hyperfine field of 45 kG is transferred to the tin nuclei.     

Defect structures of ion-implanted α-tin

Single crystalline and polycrystalline -tin has been implanted at room temperature with 80-keV ions of radioactive^119m Sn,¹¹⁹Sb, and^119m Te. The radioactive nuclei decay to the Mössbauer level of¹¹⁹Sn. Mössbauer spectra of the emitted 24-keV radiation have been measured for different source temperatures by resonance counting techniques. Five individual lines in the spectra are characterized mainly by their isomer shifts and Debye temperatures. From these parameters the radiogenic¹¹⁹Sn atoms are concluded to be located in regular substitutional and interstitial lattice sites and in defect complexes. Simple models for the defects are proposed: A Sn-vacancy pair consists of Sn atoms on (nearly) substitutional sites with a dangling bond into an adjacent vacancy. In a complex oxygen-containing defect the Sn atoms have approximately a 5s ² configuration withp-bonds to two nearest neighbour atoms. Sn atoms, having an atomic 5s ² 5p ² configuration and large vibrational amplitudes, are concluded to be in non-bonding regular interstitial sites. For special implantation conditions minor fractions of SnO₂ molecules are formed in the bulk. The interstitial¹¹⁹Sn and the¹¹⁹Sn-vacancy pairs are proposed to represent elementary point defects in -tin. Conclusions are also drawn concerning the lattice location and the defects created in the implantation process of the implanted parent isotopes.     

A Mössbauer study of FeSn2 at 100 K in applied fields

⁵⁷Fe and¹¹⁹Sn Mössbauer spectra have been recorded at 100 K in applied fields of 32 and 64 kG on a FeSn₂ sample obtained by arranging single crystal needles side by side. The present work confirms that the Sn fields are anisotropic above T_t=93 K. The field model has been used to determine the magnetic structure of FeSn₂ below T_t.     

Mössbauer measurement of the hyperfine magnetic field AT sp site in Heusler alloys Rh2 Mn Z (Z=In and Sb)

We have investigated the systematics of hyperfine magnetic field on a fixed probe at the Z-site in Heusler alloys Rh₂MnZ as the valence of Z (sp element) is varied. The hmf on¹¹⁹Sn in Rh₂MnIn_.98 ¹¹⁹Sn₀₂ has been measured at 293K and 77K. In Rh₂Mn_1.12Sb_.86 ¹¹⁹Sn_.02 the hmf on¹²¹Sb has been measured at 77 K, and on¹¹⁹Sn at 293 K and 77 K. The results are compared with the hmf on¹¹⁹Sn in Rh₂Mn Ge_.98 ¹¹⁹Sn_.02 Rh₂Mn Sn, and Rh₂Mn Pb_.98 ¹¹⁹Sn_.02.Supported by the University Research Council, University of CincinnatiSupported by the Natural Sciences and Engineering Research Council of Canada     

Magnetic properties of TbMn6Sn6-xGax (x=0.0－1.2) compounds

Effects of Ga substitution for Sn on the structure and magnetic properties of TbMn₆Sn_6-xGa_x (x=0.0－1.2) compounds have been investigated by means of x-ray diffraction, magnetization measurement and ¹¹⁹Sn M?ssbauer spectroscopy. The substitution of Ga for Sn results in a decrease in lattice constants and unit-cell volumes. The magnetic ordering temperature decreases monotonically with increasing Ga content from 423 K for x=0.0 to 390 K for x=1.2. At room temperature, the easy magnetization direction changes from the c-axis to the ab-plane. This variation implies that the substitution of Ga for Sn leads to a decrease in the c-axis anisotropy of the Tb sublattice. An increase in the non-magnetic Ga concentration results in a monotonic decrease of the spontaneous magnetization M_s at room temperature. Since there are three non-equivalent Sn sites, 2c (0.33, 0.67,0), 2d (0.33, 0.67,0.5) and 2e (0,0,0.34) in the TbMn₆Sn_6-xGa_x compounds, the ¹¹⁹Sn M?ssbauer spectra of the TbMn₆Sn₆ and TbMn₆Sn_5.4Ga_0.6 compounds can be fitted by three sextets. The hyperfine fields (HFs) decrease in the order of HF(2d)>HF(2e)>HF(2c), which is in agreement with the magnetic structure.     

Magnetism of ErAgSn studied by 119Sn Mössbauer spectroscopy

Antiferromagnetic ErAgSn compound was investigated in detail by ¹¹⁹Sn Mössbauer spectroscopy in a temperature range between 2.2 and 300 K. The ¹¹⁹Sn spectra recorded below 4.2 K can be well fitted with a single main magnetic component in agreement with recent neutron diffraction studies [1]. A broad distribution of magnetic hyperfine fields observed above 4.2 K and enhanced spin correlations among Er³⁺ ions at T > T _N = 5.6 K are the remarkable features of the investigated system.     

Mössbauer spectroscopy of laser annealed tellurium implanted silicon (I).119Sn and125Te

Laser annealed Te-implanted silicon has been investigated using¹¹⁹Sn and¹²⁵Te Mössbauer spectroscopy. The¹¹⁹Sn Mössbauer spectra consist of a single lorentzian, known to be due to substitutional Sn atoms in Si, independent of the type of doping of the silicon. The results on¹²⁵Te revcal at least two different components. In heavily doped n-type Si a single line component is observed with an isomer shift of 0.15 (5) mm/s with respect to SnTe and an effective Debye temperature of 207 (3) K. Heavy p-doping leads to another single line component with an isomer shift of ?0.13 (5) mm/s and an effective Debye temperature of 232 (3) K. These components are ascribed to the neutral and doubly positive charge state of substitutional Te atoms, respectively.     

Mössbauer study of119Sn defects in silicon from ion implantations of radioactive119In

Radioactive¹¹⁹In⁺ ions (T _1/2=2.1 min) obtained from the ISOLDE facility at CERN have been implanted into silicon single crystals at room temperature. Mössbauer emission spectra from the 24 keV -radiation of the daughter¹¹⁹Sn have been measured by fast resonance-counting technique. Five independent lines, characterized by their hyperfine parameters and Debye temperatures, have been found in the spectra. From the bonding configurations, deduced for the Sn impurity atoms, these are concluded to be located in four different defects in the silicon lattice. Simple models are proposed for the defects.     

Hyperfine interaction and phase transitions in oxide films of zirconium alloys

Trimetallic Pt/Al₂O₃SnIn–Cl naphtha-reforming catalysts were prepared via co-precipitation route. Platinum and chlorine were introduced by the incipient wetness technique on the alumina support already doped with about 0.3 %wt of Sn to obtain about 0.3 %wt of Pt and 1.5 %wt of Cl. For the same Pt, Sn and Cl composition, indium loading ranged from 0.06 to 0.6 wt.%. The obtained catalysts were investigated by ¹¹⁹Sn Mössbauer spectroscopy between 95 and 300 K. Two Sn(IV), Sn(II) and Sn(0) environments have been identified and well characterized by their hyperfine parameters. The Lamb-Mössbauer factors have been determined for each environment and found to be 0.53, 0.27 and 0.31 for Sn(IV), Sn(II) and Sn(0) respectively. The addition of indium has been found to favour the formation of Pt_xSn alloys. ¹¹⁹Sn Mössbauer spectroscopy results show that addition of even small amount of In (0.06 wt.%) leads to the formation of a Pt₃Sn alloy. At higher indium loadings, higher amounts of Pt_xSn alloys of almost equal Pt and Sn atomic concentrations were detected. The increasing formation of Pt_xSn alloys with higher indium loading is in good correlation with a decrease of catalyst’s overall conversion and selectivity to C1 and C3–C4 paraffins and increase of isomerization selectivity.     

Ag−Sn Alloys and dental amalgams: A119Sn Mössbauer,x-ray diffraction and scanning electron microscopy study

Examination has been made on aged and fresh Ag?Sn alloys and on commercial Cu?Ag?Sn dental alloys. Although x-ray diffractograms of aged Ag?Sn showed only λ Ag?Sn and free silver,¹¹⁹Sn Mössbauer spectra exhibited Sn(IV) oxide also. A low Debye temperature showed the oxide to be in intimate dynamical contact with the metallic matrix. Upon adding mercury, the phases λ₁ Ag?Hg and η′ Cu?Sn were observed in a commercial specimen. Conversion-electron spectra of a mercury-coated disk showed the presence of λ₂ Sn?Hg and a distribution of line positions smaller than that for particulate amalgams. Internal oxidation was found to prevent amalgamation.     

Local magnetic structure and anomalies of magnetic hyperfine interactions of57Fe and119Sn nuclei in lithium aluminium ferrites

The⁵⁷Fe and¹¹⁹Sn Mossbauer spectra of ordered ferrites Li_0.5Fe_2.5−xAl_xO₄∶Sn for 0.8<x<1.0 (the compensation point region) have been studied. The spin glass type magnetic structure with the spin canting angle depending on temperature and aluminium concentration is established. Anomalies in the temperature dependence of the hyperfine magnetic field at tin nuclei have been found near the compensation point of the ferrites     

Mössbauer study of the formation of impurity-vacancy complexes in copper

The formation of impurity-vacancy complexes has been studied with ion-implanted radioactive¹¹⁹Xe and its decay products, which populate the¹¹⁹Sn Mössbauer state via the decay chain¹¹⁹Xe→¹¹⁹I→¹¹⁹Te→¹¹⁹Sb→¹¹⁹Sn. The results of these implantations arecompared to those from earlier¹¹⁹In or Sbimplantations.     

119Sn Mössbauer study of the CePtSn Kondo compound

We have measured¹¹⁹Sn Mössbauer spectra of the CePtSn and (Ce_0.9La_0.1)NiSn compounds in the range from 1.5 to 293 K. In CePtSn, the spectra observed above 8 K are well explained by an electric quadrupole interaction. The spectral shape changes below 8 K due to the presence of a magnetic hyperfine field produced by the ordering of the Ce magnetic moments. We have analyzed these spectra assuming an incommensurate magnetic structure. The temperature dependence of the magnetic hyperfine field matches with anS=1/2 mean field curve with a step at 5 K. In (Ce_0.9La_0.1)NiSn, no magnetic order exists down to 1.5 K.     

金属间化合物PrMn6Sn6的结构、磁性与119Sn穆斯堡尔谱研究

采用电弧熔炼法制备了金属间化合物PrMn₆Sn₆.X射线衍射表明该化合物具有HoFe₆Sn₆型(空间群为Immm)晶体结构.磁测量表明该化合物为铁磁性，居里温度为325　K.在15—360　K范围内测量了¹¹⁹Sn穆斯堡尔谱，得到了8个Sn原子晶位的转移超精细场随温度的变化，并且讨论了Mn亚晶格与Pr亚晶格的磁有序方向. 关键词： 6Sn₆')" href="#">PrMn₆Sn₆ 穆斯堡尔谱 磁结构     

Covalency effects on implanted119Sn in group IV semiconductors studied by Mössbauer and channeling experiments

Radioactive^119mSn has been implanted with an isotope separator in single crystals of germanium, silicon, and diamond. Implantations of low doses (～10¹³ atoms/cm²) at room temperature were performed as well as of higher doses at temperatures of about 400°C. The Mössbauer spectra of these sources show mainly one line. This line originates from^119mSn on substitutional lattice sites as determined from channeling experiments with 2 MeV He⁺ ions on the same samples. The observed systematics of the isomer shifts for¹¹⁹Sn is explained on the basis of the average electronic configuration ns ^Z _snp ^Z _p characterizing chemical bonding in the host crystals. The Debye-Waller factors measured at room temperature are compared to values calculated in a high temperature approximation which accounts for impurity-host mass difference.