On the measurement of electronic spin-scattering anisotropy in the presence of magnetic interaction effects, using the dHvA Waveshape Analysis method

We derive an expression for the harmonic content of the oscillatory magnetization (de Haas-van Alphen effect) which is valid in the most general case, when the harmonic amplitudes and the relative harmonic phases of the pure Lifshitz-Kosevitch (LK) theory are modified by an arbitrary combination of magnetic interaction (MI), spin-scattering anisotropy (SSA) and exchange shift effects. The calculation produces several conclusions which bear directly upon the possibility of generally being able to determine separately the up-spin and down-spin conduction electron lifetimes in the presence of magnetic impurities, by means of measurements of the amplitudes and relative phase of the fundamental and second harmonic dHvA oscillations. We have shown that not only does SSA shift the first and second LK harmonics in phase, by amounts₁ and₂, but SSA also shifts the second harmonic magnetic interaction component by an amount 2₁. We find that, in general, the combined effect of both MI and SSA on the observable relative phase angle, (2 ₁–₂), can either add or cancel. In the limit in which the second harmonic is dominated by the MI component it can be shown that (2 ₁–₂) goes to , regardless of the amount of SSA, so that no useful information regarding SSA can be obtained from (2 ₁–₂) in this case. Measurable quantities and measurement techniques, for the determination of SSA, are discussed briefly.Research conducted at the University of Oregon with support from the National Science Foundation (USA).     

Neutron diffraction studies of the premartensitic transformation B2 → B19′ in Ti49Ni51 single crystals

We have studied structural changes in the high-temperature B2-phase in a large single crystal at temperatures near the premartensitic transformation B2 B19. We are the first to observe an extra 1/2 (110) reflection in neutron diffraction patterns taken along the [110]_B2 direction as the sample is cooled below 420 K, but still far from the martensite start temperature (M_s=180 K). This extra reflection heralds the formation of long-range order in atomic displacements with wave vectorq=(1/2±)[110]2/a. Premartensitic diffraction effects (caused by the development and correlation of lattice waves of atomic displacements with wave vectorsq ₁2/a[1/3, 1/3, 0] andq ₁2/1[1/3, 1/3] that were clearly visible in this same single crystal before the martensitic transformation B2 R, appeared at even lower temperatures with substantially lower intensities.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 56–61, January, 1995.     

Do quasiparticles in high-Tc superconductors condense like molecules of a perfect gas in the bose-Einstein condensation?

Far IR transmission spectra of very thin YBaCuO films in the 10–40 cm^–1 range have now sufficient accuracy and reproducibility to show that the number of quasiparticles at temperature <_c, _c being the transition temperature, do not follow a ⁴ law, but rather a ^1.5 one.     

High-temperature resistivity of Ti1-X Al X alloys

We have measured the high-temperature resistivities of dilute Ti_1-x Al _x alloys withx0.135 up to 1100 K (2.6 _D , where _D is the Debye temperature). We observe that possesses a strong downward deviation from a linear temperature-dependence at high temperatures (several hundred degrees Kelvin). Eventually, saturates to a constant. This non-Bloch-Grüneisen-like behavior is compared with the predictions of current theories.     

Influence of Nonplanar Distortions of the Tetrapyrrole Macroring on the Electronic States of the Tetraphenylporphin Dication

Quantum-chemical calculations of the electronic structure of the tetraphenylporphin dication have been made by the CNDO/S method for various values of the parameter of saddle-like distortions of the porphyrin macroring of angle and the dihedral angle between the macroring planes and the phenyl rings. It is shown that the boundary highest occupied molecular orbital (HOMO) of symmetry a _2u is the most sensitive to variations in and and its order can be changed relative to another HOMO of symmetry a _1u . The behavior of the lower excited electronic singlet and triplet states depending on and has been analyzed in detail. In particular, the addition of configurations with charge transfer to the Q, B, and N states as well as to the T ₁ and T ₂ states has been determined quantitatively. An interpretation of the experimental spectra of porphyrin dications on the basis of the calculation results is given.     

Probability distribution of internal distances of a single polymer in good solvent

IfP _ij(x) is the probability distribution function of the scaled distancex between two elementsi andj of a long polymer in a good solvent, it is shown by Monte Carlo calculations that is in good agreement with out data for allx (B is a normalization constant). As a model we consider the freely jointed chain consisting ofN=160 rigid links. We estimate the exponents to ₀=0.27±0.01, ₀=2.44±0.02 (fori=1,j=N); ₁=0.55±0.06, ₁=2.60±0.15 (fori=1,j=N/2); ₂=0.9±0.1, ₂=2.48±0.06 (fori=N/4,j=3N/4). ₀ and ₀ are in agreement with ₀=1/(1-v) and ₀=(-1)/v proposed by Fisher and des Cloiseaux respectively, but we find concerning ₁ and ₂ that our estimates differ from recent -expansion calculations, by an amount of 20–30%. We analyse the crossover between the various exponents.     

A new theory on scattering of electrons due to spiral dislocations

The topologically singular lattice structure around a spiral dislocation scatters electrons in a manner much different from the deformation-potential-scattering. Thet-matrix is represented ast(k, k)=t ₀ sin (k _z/2) exp (±i _kk/2)/sin ( _kk/2) with the scattering angle _kk, the componentk _z of the wave vector parallel to the dislocation, andt ₀(Fermi energy). This kind of scattering alone does not cause a perpendicular resistivity, but in a dirty limit a specific dislocation resistivity does exist, whose relaxation time per unit length of dislocation is of the order of/(Fermi energy).Work performed within the research program of the Sonderforschungsbereich 125 Aachen-Jülich-KölnOn leave of absence from Department of Materials Science, Hiroshima University, Higashisenda-machi, Hiroshima, Japan     

Streuung spinpolarisierter Elektronen an Au(110)

Using the the spin modulated polarized electron gun based on photoemission from positive affinity GaAs the intensityI(E, , ) and asymmetry (E, , ) are measured in LEED from Au(110). The asymmetry is compared with the polarizationS(E, , ) which N. Müller obtained with a Mott detector after scattering an unpolarized electron beam from the same crystal. There is excellent agreement for the (00) beams, if the scattering plane is a mirror symmetry plane of the crystal (=0°, =90°). From the differences for the (00) and (11) beams at =35° and the (01/2) beam at =90° conditions for possible models for the reconstructed Au(110)–(1×2) surface may be derived.

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Die vorliegende Arbeit ist ein Auszug aus [1]

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Neue Addresse ab 1. Oktober 1980: B. Reihl, IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA     

Thermal atomic vibrations in Cu-Ni alloys

Copper radiation has been used in an x-ray study of the temperature dependence of the effective characteristic x-ray temperature _p(T) for the alloys of the Cu-Ni system over the temperature range 293–1073 °K and in a determination of the concentration dependence of d ln_p/dT for the alloys. It is shown that _p(c) is additive. The concentration dependence of d ln_p/dT is linear. The agreement between the experimental results and data in the literature is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 75–80, September, 1970.     

Multifractal percolation and growth in intermittent media

The Havlin-Bunde multifractal hypothesis for the probability density of a random walker is used to obtain the scaling law of thepth-order correlation function of the concentration (for percolation) and of the height (for growing surfaces) differences:c _p (r)=<|(x+r)–(x)| ^p >r p in intermittent media. It is shown that near the transition to homogeneity _p =A _p In(p/p _o)(whereA andp ₀ are some constants). Good agreement with recent experiments and computer simulations of different authors is established.     

Differential equations in the spectral parameter,Darboux transformations and a hierarchy of master symmetries for KdV

We study a certain family of Schrödinger operators whose eigenfunctions (, ) satisfy a differential equation in the spectral parameter of the formB(, )=(x). We show that the flows of a hierarchy of master symmetries for KdV are tangent to the manifolds that compose the strata of this class ofbispectral potentials. This extends and complements a result of Duistermaat and Grünbaum concerning a similar property for the Adler and Moser potentials and the flows of the KdV hierarchy.     

The temperature field in a crystal during heating by radiation

An accurate solution is given of the problem of the temperature field in a crystal when radiative heat transfer is taking place on its surface and the thermophysical characteristics depend on temperature range below the Debye temperature (T < _D).     

Direction-Dependent Free Energy Singularity of the Antiferroelectric Asymmetric Six-Vertex Model

The transition from the ordered commensurate phase to the incommensurate Gaussian phase of the antiferroelectric asymmetric six-vertex model is investigated by keeping the temperature constant below the roughening point and varying the external fields (h, v). In the (h, v) plane, the phase boundary is approached along straight lines v = k h, where (h, v) measures the displacement from the phase boundary. It is found that the free energy singularity displays the exponent 3/2 typical of the Pokrovski–Talapov transition f const(h)^3/2 for any direction other than the tangential one. In the latter case f shows a discontinuity in the third derivative.     

Exact expressions for row correlation functions in the isotropicd=2 ising model

We present exact explicit expressions for the row spin-spin correlation functions _{00 n}0 in the isotropicd= 2 Ising model, in terms of elliptic integrals, forn 5. We also give a general structural formula for _{00 n}0.     

Measurement of the reaction γp → K0Σat photon energies up to 2.6 GeV⋆

The reaction p K⁰⁺ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross-section and the polarization of the ⁺ as a function of the kaon production angle in the centre-of-mass system, cos^c.m._K, and the photon energy. The cross-section is lower and varies less with photon energy and kaon production angle than that of p K⁺⁰. The ⁺ is polarized predominantly at cos^c.m._K 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.     

Symmetries of Einstein-Yang-Mills fields and dimensional reduction

LetE be a manifold on which a compact Lie groupS acts simply (all orbits of the same type);E can be written locally asM×S/I,M being the manifold of orbits (space-time) andI a typical isotropy group for theS action. We study the geometrical structure given by anS-invariant metric and anS-invariant Yang Mills field onE with gauge groupR. We show that there is a one to one correspondence between such structures and quadruplets of fields defined solely onM; _v is a metric onM,h are scalar fields characterizing the geometry of the orbits (internal spaces), ⁱ are other scalar fields (Higgs fields) characterizing theS invariance of the Lie(R)-valued Yang Mills field and is a Yang Mills field for the gauge groupN(I)|I×Z((I)),N(I) being the normalizer ofI inS, is a homomorphism ofI intoR associated to theS action, andZ((I)) is the centralizer of(I) inR. We express the Einstein-Yang-Mills Lagrangian ofE in terms of the component fields onM. Examples and model building recipes are given.     

Correlation functions and pressure of a nonisothermal plasma

Expressions are obtained for the correlation functions of a classical nonisothermal two-component plasma. In the limiting case _{e i} strong correlations arise because of the presence of weakly-damped waves (ion acoustic waves) with a phase velocity lying between the thermal velocities of the particles u_e /k u_i. Under such conditions the correction to the pressure because of Coulomb interaction changes sign in comparison with the case of thermodynamic equilibrium, when there are no such waves.     

Specific heat ofd-hcp and fcc lanthanum under high pressure

Specific heat measurements have been performed under pressures up to 2.5 GPa on single phased-hcp lanthanum and a mixed phase sample yielding also results on fcc La. An evaluation of the pressure dependences of the Debye temperature _D and the electronic specific heat coefficient has been possible and shows distinct differences between the two phases. While for thed-hcp phase marked variations with pressure have been found, there is hardly no change seen in fcc La. Ind-hcp La the most remarkable results are an initial increase of , which cannot be explained by the increase of the electron-phonon coupling parameter alone and, therefore, indicates an increase of the band structure density of states, as well as a strong softening of _D at higher pressures. These results are discussed in the context of the existing knowledge on lanthanum.     

Analysis of Θproduction in K<Superscript>+</Superscript>- Xe collisions

The reaction K⁺XeK⁰pX is investigated in a meson-exchange model including rescattering of the secondary protons with the aim to analyze the evidence for the ⁺(1540)-resonance reported by the DIANA Collaboration. We confirm that the kinematical cuts introduced by the DIANA Collaboration efficiently suppress the background to the K⁺nK⁰p reaction which may contribute to the ⁺(1540) production. We find that these kinematical cuts do not produce a narrow structure in the K^0p effective-mass spectra near 1540 MeV. We study the effect of a narrow ⁺-resonance of both positive and negative parity in comparison with the DIANA data. We show that the K⁺XeK⁰pX calculations without ⁺ contribution as well as the results obtained with a ⁺ width of 1 MeV are in comparably good agreement with the DIANA results. More dedicated experiments are called for to establish this exotic baryon resonance.     

Calculation and optimization of parameters of radiating distributed feedback structures

A simple method is suggested for calculation of reflection, radiation and transmission coefficients for the distributed feedback structure in the second diffraction order. The method is based on a slight difference between coefficients of reflectionR and radiationI of the surface wave for = (where is the light wavelength corresponding to a precise resonance for the grating length I) and those for =_l (where _l is the light wavelength corresponding to the resonance for the finite grating length). The simplicity of the method makes it possible to use it for optimization of the distributed feedback structure by a number of parameters. The technique can be used in the case of thin-film and diffused waveguides for both TE and TM modes.