Internal conversion study on the contact charge density of57Fe impurity atoms in Au metal

Three different internal conversion spectra were measured on the 14.4 keV transition of⁵⁷Fe in Au metals. Adaptability of our method for analysing the line intensity, i.e. the deconvolution-reconvolution method with the constant tail fraction rule was tested experimentally. The obtained 4s electron densities, 4_s(o), of Fe impurity atoms in Au agreed on four samples within the error. The weighted mean value of 4_s(o) of Fe in Au is 4.98±0.68a ₀ ^–3 . It is concluded that the method of analysis is reasonable in this type of experiment.     

Relation between internal conversion coefficient and electron density at the nucleus for spin polarized Fe electrons

An ICC computation for the 14.4 keV transition in⁵⁷Fe has been made using relativistic wavefunctions derived from spin polarized UHF wave functions of atomic iron. It is shown that ICC and electron density at the nucleus are proportional for polarized s electrons as has been found already for unpolarized electrons.     

纳米金属镝的传导电子定域化

研究不同粒径的稀土金属镝(Dy)纳米晶块体材料的电阻率随温度的变化. 电阻率包括剩余电阻率ρ_res=ρ(0)、磁散射电阻率ρ_mag(T)和声子散射电阻率ρ_pho(T). 样品的平均粒径分别为10,30,100和1000 nm. 实验发现磁散射电阻率ρ_mag(T)和声子散射电阻率ρ_{pho 关键词： 镝金属电性 定域化 能带论 无序}     

Spin-flip scattering of conduction electrons by dislocations in a metal

The spin-flip scattering of conduction electrons by dislocations in metals with a strong spin-orbit coupling is considered. Calculations are performed in terms of the model spin-orbit potential describing the spin-flip scattering of conduction electrons. It is shown that deformation of the crystal lattice in a metal leads to a change in the structure factor. The core of a rectilinear edge dislocation is calculated by the molecular dynamics method. The results obtained are compared with the experimental data on conduction-electron spin resonance (CESR) in copper.     

Scattering of conduction electrons by surface roughness in thin metal films

A fluctuation transport theory is applied to describe the extra resistivity of thin metal films due to electron scattering at rough surfaces. This scattering mechanism is described in terms of the surface profile autocorrelation. If the lateral extension of the surface structures exceeds the Fermi wavelength, the scattering can be described by a step density of terrace edges.     

Inelastic life-time of the conduction electrons in some noble metal films

Magneto-conductance measurements of thin films of Cu, Ag and Au are reported. The measurements are evaluated with the theory of weak localization and yield for the noble metals a very good agreement with the theory in the whole field range up to 5T. No adjustment of the theoretical prefactor is necessary. The magneto-conductance curves show a pronounced structure caused by spin-orbit coupling. The measurements yield the inelastic life-time and the spin-orbit coupling of the conduction electrons for Cu, Ag and Au. _i obeys a 1/T ^p law withp=1.65.     

Room temperature Compton profiles of conduction electrons in α-Ga metal

Room temperature Compton profiles of momentum distribution of conduction electrons in α -Ga metal are calculated in band model. For this purpose, the conduction electron wave functions are determined in a temperature-dependent non-local model potential. The profiles calculated along the crystallographic directions, (100), (010), and (001) are found to be nearly isotropic. This conclusion is in reasonable agreement with experimental observations     

Spin-echo measurements of the conduction electrons self-diffusion coefficient in a metal

The principle possibility of spin echo measurements of conduction electron orbital motion parameters is experimentally demonstrated, using metallic lithium as an example.     

Deformation of a charge density wave in the vicinity of a point contact with a normal metal

The current-voltage characteristics of Cu-K_0.3MoO₃ point contacts between a metal and a semiconductor with a charge density wave (CDW) are studied for various diameters of the contacts in a wide range of temperatures T and voltages V. In the interval 80 K ? T ? 150 K, the current-voltage characteristics are correctly described in the framework of a semiconductor model: screening of an external electric field causes CDW deformation, shifts the chemical potential of quasiparticles, and changes the point contact resistance. It is shown that the chemical potential is above the middle of the Peierls gap in equilibrium and approaches the middle upon an increase in temperature. The current-voltage characteristics of point contacts with a diameter d ? 100 Å exhibit a sharp decrease in resistance for |V| > V _t , which is associated with the beginning of local CDW sliding within the contact region. The V _t (d, T) dependence can be explained by the size effect in the CDW phase slip.     

Observation of a high spin polarization of secondary electrons from single crystal Fe and Co

The spin polarization of secondary electrons with nearly zero kinetic energy from Fe (100) and Co (10$\text{1}$0), excited with photons of energy between 20 and 60 eV, was found to be 45%±5% for Fe and 35%±5% for Co. This value is higher than the average valence band spin polarization P_b=n_b/n=2.2/8=27% and 1.7/9=19% for Fe and Co, respectively. With increasing kinetic energy, the spin polarization of the secondaries decreases to the value of P_b within the first 5 eV, remaining constant (within statistical error) at higher kinetic energies. As a spin dependent scattering process we propose excitations within the d-bands, which can be shown to be asymmetric with respect to the electron spin. The high net spin polarization of the slowest emitted electrons is obtained by filtering out monitory-spin electrons at the vacuum barrier.     

The charge states of iron in insulators implanted with57Co and57Fe

Single crystals of α-Al₂O₃ and LiNbO₃ were implanted with⁵⁷Co (dose: up to 2×10¹⁵ atoms/cm²) and with⁵⁷Fe (dose: 2×10¹⁵ atoms/cm²) ions. The Mössbauer spectra revealed the disordered atomic environment. Fe²⁺ and Fe³⁺ charge states were observed. The spectra were compared to the spectra of crystals doped with⁵⁷Co. It was remarkable that in the doped α-Al₂O₃ Fe³⁺ states with slow spin-spin relaxation have appeared. The CEMS study of the samples implanted with⁵⁷Fe resulted in Fe²⁺ ionic states indicating that a fraction of Co atoms can also be in Co²⁺ state.     

Exchange energy for conduction electrons in (ZnMn)Se derived from spin-flip Raman scattering and magnetization

Spin-flip Raman scattering, magnetization, and susceptibility data for Zn_0.97Mn_0.03Se are reported. The exchange energy N_oα = 243 ± 10 meV for the conduction electrons is obtained from an analysis of the Raman and magnetization data. At large magnetic fields (H > 60 kOe), the spin-flip energy ΔE saturates at 14 meV. At low fields ΔE does not extrapolate to zero as H → 0, which is characteristic of scattering from donor-bound electrons. The low temperature magnetization curves are fit to a modified Brillouin function. The fit gives $\text{x}\text{?}\text{/x}\text{= 0.67}$ as the fraction of active magnetic ions, and an effective temperature T_eff = T + T_o with T_o = 1.1 K. The magnetic susceptibility follows a Curie-Weiss law between T = 150 and 280 K with a Curie-Weiss temperature θ = ?33 K.     

Fe1+−Fe2+ charge transfer process after57Co decay in ZnTe

We have performed Mössbauer absorption and emission experiments on⁵⁷Fe impurities in ZnTe. A transient Fe¹⁺ charge state has been observed below 130 K in the emission spectra. The dynamics of the Fe¹⁺?Fe²⁺ charge transfer was shown to obey an activation process with an activation energy of 0.09 eV. Low temperature Raman relaxation rates within the Fe²⁺ spin-orbit levels are found to be at least 100 times faster in ZnTe than in ZnS.     

Dynamics of localized spins coupled to the conduction electrons with charge and spin currents

The dynamics of the localized spins coupled to the conduction electrons is studied theoretically in the wide range of magnitudes of the charge and spin currents including the regime which has never been explored but is now possible in terms of the pure spin-current injection methods, e.g., the spin Hall effect and spin battery. The equations of motion for the two-spin system are investigated in detail, and its phase diagram of the dynamics is presented. It is found that the dynamics depends sensitively upon the relative magnitudes of the charge and spin currents; i.e., it shows steady state, periodic motion, and even chaotic behavior. The extension to the multispin system and its implications including a possible "spin-current detector" are also discussed.     

Spin density distribution of the conduction electrons in diperylene hexafluorophosphate analysed by high-resolution NMR

High-resolution ¹³C nuclear magnetic resonance with ¹H cross polarization and ¹H decoupling under magic angle spinning is measured for the quasi-one dimensional organic conductor diperylene hexafluorophosphate (including tetrahydrofurane solvent molecules) at temperatures between 160 K and 270 K. Ab initio molecular orbital calculations are used for chemical shift analysis and for assignment of Knight shifted lines and individual carbon positions. The coexistence of neutral perylene molecules and perylene radicals in the same radical cation salt is revealed. From Knight and chemical shifts we were able to distinguish two inequivalent perylene radicals within the conducting stack. The spin density distribution of the molecular electronic wave function is determined quantitatively for these radicals. Received 29 June 1999 and Received in final form 4 November 1999     

The spin polarization of conduction electrons in ferromagnetic semiconductors

Within the framework of the s?f exchange model the exact asymptotics of the spin polarization of conduction electrons in the non-degenerate ferromagnetic semiconductor at low temperatures is calculated. It is demonstrated that the temperature dependent corrections to the total density of states are proportional to $\text{T}{}^{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$.     

Joint density of states and charge density wave in 2H-structured transition metal dichalcogenides

The joint density of states of two different 2H-structured transition metal dichalcogenides (TMDs) with and without charge density wave (CDW), Na_0.05TaS₂ and Cu_0.09NbS₂, respectively, are compared. While there is a clear maximum at the 3×3 charge density wavevector for Na_0.05TaS₂, the joint density of states for Cu_0.09NbS₂ does not show such behavior, consistent with the absence of CDW in the system. Our results illustrate that the joint density of states well represents the charge instability in 2D systems.     

Interaction of conduction electrons in solids

It is shown that the influence of the interaction of conduction electrons with phonons can be partly included in the potential energy of their interaction. The effective potential energy found is used to study the possibility of the existence of bound states of two electrons in polar, homopolar and metallic crystals.     

Elastic properties of linear charge density wave materials in the regime of nonlinear conduction

The Young's moduli E of TaS₃, (TaSe₄)₂I, and NbSe₃ are found to soften when the samples are subjected to voltages V in excess of the threshold V_T for nonlinear electrical conduction by sliding charge density waves. The voltage dependences of E are similar to the voltage dependences of the differential resistance and of the dielectric constant. The difference in stiffness for V < V_T and V >> V_T is ascribed to decoupling of distortions of the charge density wave from those of the underlying lattice.     

The propagator of conduction electrons in semiconductors with a delta-barrier or a delta-well potential II. The electron density profile

The density of the conduction electrons near a delta-barrier and near a delta-well is calculated in a one-dimensional non-degenerate semiconductor, on condition that interband transitions may be neglected. The dispersion function E(k) in the bottom part of the conduction band is fitted by a function resulting from the author's theory of the Wiener process modified by a Poisson random sequence of very short shocks [V.B., J. Phys.: Math. Gen. 25 (1992) 6027]. In an interval (which is wide enough), this function can simulate the Kane (two-band) dispersion function with the non-parabolicity parameter = 1/E _G.