Optical and magnetooptical characterization of FeNi/Cu multilayers

A series of [FeNi(1.7 nm)/Cu(t_Cu)]₃₀/Fe(10 nm) multilayers with the range of t_Cu from 0.36nm to 4.32nm deposited on glass substrates was studied by measuring the effective optical constants n and k, saturation magnetooptical polar Kerr rotation θ _k and ellipticity η_k and evaluating the effective complex off-diagonal elements of the dielectric tensor ε _xy ^′ and ε _xy ^″ . It was found that the four primary quantities ε _xy ^′ , ε _xy ^″ , n and k vary concurrently with respect to t_Cu, while the dependences of θ _k and η _k on t_Cu differ drastically. To explain this difference the contributions of both the real and imaginary parts of the off- diagonal dielectric tensor elements and the effect of complex optical constants have to be considered. No obvious correlation was found between the variation of ñ, ε~ _xy and the oscillations of GMR of the multilayers.     

Nanoscale distortions of the lattice of a ZnSe crystal doped with 3d elements

The structure of semiconductor crystals Zn_1?x V _x ²⁺ Se (x = 0.0018) and Zn_1?x Cr _x ²⁺ Se (x = 0.0006) was studied for the first time using thermal neutron diffraction at 300 and 120 K. The diffraction patterns of the crystals were revealed to contain diffuse scattering regions near the Bragg reflections of the initial cubic lattice. The experimental results are discussed in combination with earlier obtained data on neutron diffraction and propagation of ultrasonic waves in Zn_1?x Ni _x ²⁺ Se (x = 0.0025) and Zn_1?x Cr _x ²⁺ Se (x = 0.0029). The diffuse scattering is shown to be due to nanoscale shear strains of the ZnSe lattice. The character of these strains is determined by Jahn-Teller 3d ions.     

Parametrization of two-body perturbation on atomic fine and hyperfine structure. The configuration (6p)3 in the bismuth atom

A method of simultaneous parametrization of one- and two-body interactions on atomic hyperfine structure of configurationl ^N is proposed and applied for the analysis of the configuration (6p)³ in the bismuth atom. For this purpose, the hyperfine structure splittings of the levels²D ₃ ^2/0 ,²D ₅ ^2/0 and²P ₁ ^2/0 were measured. The finally obtained values of HFS parameters are: for one-body parameters (in MHz):a _p ⁰¹ =2,537(9),a _p ¹² =5,182 (12),a′¹⁰=?2,019(10),b _p ⁰² =?3,198(53),b _p ¹¹ =2,816(54); for two-body parameters (in MHz):x _pp ^′/01 ,₂=284(3),x _pp ^′/12 ,₂=581(5),x _pf ^′/12 ,₂=170(70),x _pp ^′/02 ,₂=?359(36),x _pf ^′/02 ,₂=?33(100). The value of the quadrupole moment of the nucleus ₈₃ ²⁰⁹ Bi is also discussed.     

The potential for which E n 1 ′ 12=E n 2 ′ l1 in nonrelativistic quantum mechanics

The answer is provided to the question ‘What is the potential for which E _{n 1} ^′ l₂=E _{n 2} ^′ l₁ in nonrelativistic Quantum Mechanics?’     

Investigation of N 2 + (C 2Σ u + → X 2Σ g + fluorescence excited through auger decay of the 1s −1π* resonance

A theoretical investigation of N ₂ ⁺ (C ²Σ _u ⁺ → X ²Σ _g ⁺ molecular fluorescence excited through the Auger decay of the 1s ^?1π* resonance is carried out. The fluorescence cross sections are calculated with due regard for the dependence of the matrix element of the C → X dipole transition on the internuclear distance, the interference between channels of excitation via different vibrational levels v _r of the 1s ^?1π* resonance, the rotational structure of the fluorescence band, and the predissociation of the N ₂ ⁺ C ²Σ _u ⁺ v′ ≥3) states. The calculated cross sections are in good agreement with the experimental results of recent measurements. The results of the calculations have demonstrated that the observed dependence of the cross section of the (C ²Σ _u ⁺ (v′) → X ²Σ _g ⁺ (v″) fluorescence on the excitation energy and the fluorescence wavelength for a group of bands with equal values of the difference Δv = v′ ? v″ is associated with transitions between the vibrational levels of the electronic states involved in the excitation and subsequent cascade decay of the 1s ^?1π* resonance: N₂ (v ₀ = 0) → N*₂(1s ^?1π*(v _r)) ? N ₂ ⁺ : (C ²Σ _u ⁺ (v′) → X ²Σ _g ⁺ (v″).     

Cation distribution of the system Zn1−xCoxFeMnO4 by x-ray,electrical conductivity and Mössbauer studies

Structural, electrical and Mössbauer studies were carried out for the system Zn_1?xCo _x Fe MnO₄. It is observed that forx?0.6, the ionic configuration of the system is Zn _1?x ²⁺ Mn _x ²⁺ [Co _x ³⁺ Mn _1?x ³⁺ Fe³⁺]O ₄ ^2? and forx?0.8 Fe³⁺ ions occupy tetrahedral site also. On the basis of electrical and Mössbauer studies a probable valence distribution of CoMnFeO₄ has been suggested. All the compounds showed positive values of thermoelectric coefficient and electrical conduction takes place by a hopping mechanism. Activation energy and thermoelectric coefficient values decreased with decrease in concentration of Zn²⁺ ions. The compounds possess low mobility values varying between 10^?7 and 10^?9 cm²/V sec.     

Spin states of cobalt and the thermodynamics of Sm1 − x Ca x CoO3 − δ solid solutions

In the rare-earth SmCoO₃ perovskite, Co³⁺ ions at low temperatures appear to be in the low-spin state with S = 0, t _2g ² e _g ⁰ . If Ca²⁺ ions partially substitute Sm³⁺ ions, oxygen deficient Sm_{1 ? x} Ca _x CoO_{3 ? δ} solid solutions with δ = x/2 appear. The oxygen deficiency leads to the formation of pyramidally coordinated cobalt ions Co _pyr ³⁺ in addition to the existing cobalt ions Co _oct ³⁺ within the oxygen octahedra. Even at low temperatures, these ions have a magnetic state, either S = 1, t _2g ⁵ e _g ¹ or S = 2, t _2g ⁴ e _g ² . At low temperatures, the magnetization of Sm_{1 ? x} Ca _x CoO_{3 ? δ} is mainly determined by the response of Co _pyr ³⁺ ions. Owing to the characteristic features of the crystal structure of the oxygen deficient perovskite, these ions form a set of nearly isolated dimers. At high temperatures, the magnetization of Sm_{1 ? x} Ca _x CoO_{3 ? δ} is mainly determined by the response of Co _oct ³⁺ ions, which exhibit a tendency to undergo the transition from the S = 0, t _2g ⁶ e _g ⁰ state to the S = 1, t _2g ⁵ e _g ¹ or S = 2, tt _2g ⁴ e _g ² state. In addition, the magnetization and specific heat of the solid solutions under study include the contribution from the rare-earth subsystem, which undergoes a magnetic ordering at low temperatures.     

The decay of the Bethe-Salpeter kernel inP(ϕ)2 quantum field models

We extend methods of high temperature expansions to show that for even weakly coupledP(?)₂ quantum field models the Bethe-Salpeter kernel has 4 particle decay. More precisely ifK denotes the Euclidean Bethe-Salpeter kernel $$|K(x_1 ,x_2 ,x_3 ,x_4 )| \leqq Oe^{ - m_0 (1 - \varepsilon )d_2 } ,$$ wherex=(x ⁰,x ¹),d ₂=2|x ₁ ⁰ +x ₂ ⁰ ?x ₃ ⁰ ?x ₄ ⁰ |+|x ₁ ⁰ ?x ₂ ⁰ |+|x ₃ ⁰ ?x ₄ ⁰ | and ε(λ)→0 as λ→0. Our methods apply to otherr particle irreducible kernels.     

Theory of nonstoichiometric ordering of Pb-containing relaxors with perovskite structure

Conditions that are imposed on the interatomic interaction and under which a certain ordered state of AB _x ^′ B _1?x ^″ perovskites arises are determined with allowance for effectively pairwise interactions and the configuration entropy of interchanges of B′ and B″ ions. It is shown that, for the interaction potential u(R) = u ₀/R ⁶, the highest temperature of ordering of the 1: 2 type (T _ord (1: 2)) corresponds to a structure observed at A ≡ Ba. The highest temperature of ordering of the 1: 1 type (T _ord (1: 1)) corresponds to a structure that typically occurs in the case of A ≡ Pb. Within the approximation used, it is found that T _ord (1: 1) > T _ord (1: 2) for all compositions and that the 1: 1-ordered phase is most stable. For models with u(R) = u ₀/R ⁿ (n = 1–6) including the interaction in the first m coordination shells (m = 3, 6, 8, 11), it is shown that the ground state of AB _x ^′ B _1?x ^″ O₃ corresponds either to a decomposed solid solution or to an ordered state similar to that observed in PbMg_1/3Nb_2/5O₃.     

Phase transitions in manganites with substitution of divalent ions for manganese

Experimental data are presented for the position of phase boundaries “orthorhombic-rhombohedral structure” and “semiconductor-metal” in manganites of La_{1 ? c + x} Sr _{c ? x} ²⁺ Mn_{1 ? x} Me _x ²⁺ O_{3 + γ} (Me = Mg, Zn, Ni) systems depending on the concentration of substituting divalent cations (0.15 ≤ c ≤ 0.35; 0.025 ≤ x ≤ 0.100).     

Resonance strengths,branching ratios and mean lifetimes of nuclear energy levels in23Na

The gamma decay of the²²Ne(p, y)²³Na resonances in the proton energy rangeE _p=1.0→2.0 MeV has been investigated with a 20cm³ Ge(Li) detector. Implanted targets were used. The absolute strengths of the strongest resonances were determined and the branching ratios of twenty resonance levels and several bound states are reported. Mean lifetimes of the levels atE _x=2.078 MeV (18.7±3.5 fs), 2.393 MeV (580 _?190 ⁺³⁷⁰ fs), 2.641 MeV (88 _?14 ⁺²⁰ fs), 2.985 MeV (4.0 _?1.0 ^+1.3 fs), 3.679 MeV (24 _?4 ⁺⁵ fs), 3.915 MeV (7.4 _?2.0 ^+2.5 fs) and 4.775 MeV (<2.0 fs) were obtained from measurements of the gamma ray Doppler shifts.     

90° pulsed magnetization of ferrite-garnet films with easy-plane anisotropy

The process of pulsed 90° magnetization of ferrite-garnet films was studied. These films, in addition to easy-plane anisotropy, have biaxial anisotropy in the film plane with an effective field H _K2 ? 40–55 Oe. the pulsed magnetization curve contains two portions separated by a kink observed at a field pulse amplitude H _p=H _p ^* ? 16–18 Oe. An analysis of the magnetization signals showed that the restoring torque, which is mainly caused by biaxial-anisotropy forces, is overcome in fields H _p ≥ H _p ^* and that magnetization rotation occurs. In fields H _p < H _p ^* , the magnetization vector rotates at the initial stage only and the angle of rotation ?_in is less than 25°–26°. The field H _p ^* and angle ?_in are calculated. The results of the calculations are confirmed by experimental data. In fields H _p > H _p ^* , the process of magnetization is accompanied by oscillations of the magnetization vector. In contrast to free magnetization oscillations, these oscillations are nonlinear and the frequency of the first harmonic (≈5 × 10⁸ Hz) is much lower than that for free oscillations, (7–12) × 10⁸ Hz. Oscillations are excited at a pulse rise time of ≈6 ns.     

New screening doublets in x-ray satellite spectra

Recent scrutiny of the relevant data available at present on x-ray satellite spectra in theK, L andM regions revealed the existence of two new satellite pairsα″α′ andα″α′ ₃ ′ in theKα satellite group, three pairsα′ ₂ α″,α′ ₂ α^VI andα? α ^IV in theLα satellite group, twoLβ ₂ satellite groups; viz.,β ₂ ^(b) (β ₂ ^I ,β ₂ ^II β ₂ ^(c) ) andβ ₂ ^(c) (β ₂ ^I β ₂ ^II ), two pairsγ′₁ γ′₂ andγ′₁ γ′_2′ in theLγ satellite group and also a pairβ _II β _III in theMβ satellites, which are all found to be governed by the screening doublet relationship,Δ(v/R)^1/2=constant.     

About the nature of Ni3+ magnetic centres in the LaSrAl1−xNixO4 ceramics

LaSrAl_1?x Ni _x 0₄ (x≤0.11) ceramics werer studied by EPR. It was established that Ni³⁺ ions in this compound may be in two states: a low spin one with t _2g ⁶ e _g ¹ electron configuration and high spin state with t _2g ⁵ e _g ² electron configuration. It was shown that the random distribution of La³⁺ and Sr²⁺ ions in the heavy metal sublattice leads to two kinds for each type of these centres with different degree of tetragonal distortions. The total concentration of NiO₆ isolated centres in these ceramics does not exceed 5–10 % of a total number of nickel ions at a givenx. A model, explaining these peculiarities observed in an experiment by the enhanced tendency of Ni³⁺ ions to clusterization, was proposed. It appears that even at small concentrations Ni³⁺ ions form clusters and conglomerates, whose structural characteristics of the oxygen octahedra are comparable with those in LaSrNiO₄.     

Jahn-Teller effect in low-spin Ni3+ in the LaAlO3 ceramic

This paper reports on an EPR study of LaAl_1?x Ni_xO₃ solid solutions with x≤0.12 made in the 4.2-to 300-K temperature range. In the X range, the broadening of the single EPR line with g _eff=2.148 was observed at temperatures below ～40 K. In the Q range, a slightly anisotropic EPR line with g _⊥ ^′ =2.145±0.002 and g _‖ ^′ =2.154±0.002 transforms to a rhombic-symmetry spectrum with g ₁=2.183±0.002, g ₂=2.143±0.002, and g ₃=2.118±0.002. It is shown that the observed low-temperature effects are due to the lowered symmetry of the complex under the combined action of the tetragonal Jahn-Teller distortions and of the trigonal component of the crystal field.     

Role of an acceptor impurity in the proton transfer in proton-conducting oxides

The influence of interaction of protons with defects (acceptor impurities, oxygen vacancies) and with each other on the proton transfer in acceptor-doped proton-conducting oxides A ^II B _1?x ^IV R _x ^III O_{3 ? δ} with the perovskite structure and in oxides A _2?x ^III R _x ^II O_{3 ? δ} with the structure of a distorted fluorite (bixbyite) has been investigated theoretically. The tracer diffusion coefficient D* and proton mobility have been calculated by the Monte Carlo method and analytically. It has been shown that the interaction of protons with defects substantially affects the magnitude and behavior of the transfer coefficients. The interaction with acceptor impurities plays the most important role. The proton mobility significantly decreases even at a low dopant concentration (x ～ 1–3 at %). The dependence of the proton conductivity σ on the impurity concentration can exhibit maxima. For oxides with the bixbyite structure including nonequivalent cation sites, the distribution of the dopant over these sites has a strong influence on the dependence σ(x). The obtained results have been used to interpret the experimental data on the proton conductivity for a number of oxides.     

Full destruction characteristics of light and heavy nuclei with 3.7-158A GeV energies

The full destruction (FD, that implies the disintegration into singly and doubly charged fragments only) characteristics are presented for some light nuclei ( ₆ ¹² C, ₈ ¹⁶ O, ₁₀ ²² Ne, and ₁₄ ²⁸ Si) with an energy of 3.7A GeV and heavy projectiles ₇₉ ¹⁹⁷ Au (10.7A GeV) and ₈₂ ²⁰⁸ Pb (158A GeV) interacting with target nuclei in a photoemulsion. It is shown that (i) the average number of fragments, the realization of various fragmentation channels, and the degree of crushing for light projectiles substantially depend on the charge of a residual nucleus and on the mass of a target nucleus; (ii) the FD probability for residual nuclei with the same charge, as well as the multiplicity of fragments for the same impact parameter of heavy nuclei, are independent of the energy; and (iii) the integral distribution of transverse momenta of doubly charged fragments is described by two exponents (the logarithmic plot exhibits a break).     

Disparity in transient field characteristics for Au ions traversing Fe and Gd hosts through measurements ofg-factors in197Au

Transient field precessions were measured for levels in the nuclides of^182,184,186W and¹⁹⁷Au as their ions simultaneously traversed polarized Fe and Gd hosts. Consistent sets of gyromagnetic ratios were inferred for the lowest 5/2⁺ and 7/2⁺ states in¹⁹⁷Au using these two ferromagnetic host media, provided that (i) the transient field for Au ions in Gd is calibrated using the W in Gd precessions (simultaneously measured) and, (ii) the transient field for Au in Fe is calibrated using the field strength and velocity dependence for Pt in Fe (previously measured). The presentg-factor results are: g(5/2 ₁ ⁺ ;¹⁹⁷Au)=0.296±0.023, g(7/2 ₁ ⁺ ;¹⁹⁷Au)=0.241±0.021, and g(5/2 ₁ ⁺ ;¹⁹⁷Au)=1.2±0.2.     

Laser Raman spectra of mixed crystals of [(NH4)1−x Kx]2 SO4

The Raman spectra of mixed crystals of [(NH₄)_1?x K _x ]₂ SO₄ in the region 50–3400 cm^?1 at 293 K and below 223 K have been reported. At room temperature 293 K, as the concentration of K⁺ ion increases in the crystal up to 50%, the frequencies of the totally symmetric vibrations of SO ₄ ^2? and NH ₄ ⁺ ions increase and thereafter the frequency of SO ₄ ^2? vibration decreases and attains the value in K₂SO₄. This change in frequency up to 50% of potassium concentration is due to the breaking of hydrogen bonds of the type N-H...O. The behaviour of Raman intensities of A _g (v ₁) mode of SO ₄ ^2? for various concentrations (x=0, 0·03, 0·11, 0·5, 0·85) suggest that the phase transition changes from first order type to one of second order. The phase transition in mixed crystals of [(NH₄)_1?x K _x ]₂ SO₄ can be a cooperative phenomenon arising from a coupling between (NH₄)⁺ ions through hydrogen bonds with the distorted SO ₄ ^2? ions in the low temperature phase.