Novel intramolecular reductive C-C coupling during borohydride reduction of a bi-enone

Borohydride reduction of the bi-enone (1) gave the structurally and mechanistically interesting compounds (4) and (5a-c) resulting from intramolecular carbon-carbon coupling.

Valence states and magnetic properties of LaNi1-xMnxO3 (for 0≤x≤0.2 and x=0.5)

Single-phase LaNi1-xMnxO3 samples in the compositional range 0coupling occurs via solvent electrons in a narrow conduction band. The conductivity changes from that of a narrow-band metal for x<0.01 to that more characteristic of diffusive motion for x>0.05, but any motional enthalpy appears to remain small ( Delta Hm approximately=0). The x=0.1 sample exhibits ferrimagnetic spin glass behaviour below 40K, and the ferromagnetic interactions increase with manganese concentration. The oxide with x=0.50 is ferromagnetic with a well defined Curie temperature.

spin Precession of a Charged Particle in a Magnetic Field Including the Effects of General Relativity

Abstract is not available.

Crystal growth and characterization of two-leg spin ladder compounds: Sr14Cu24O41 and Sr2Ca12Cu24O41

Single crystals of Sr14−xCaxCu24O41 (x=0 and 12) are grown by the travelling solvent floating zone technique using an image furnace. The grown crystals are characterized for their single crystallinity by the X-ray and Neutron Laue method. The magnetic susceptibility measurements in Sr14Cu24O41 show considerable anisotropy along the main crystallographic axes. Low-temperature specific heat measurement and DC susceptibility measurement in Ca-doped crystal showed antiferromagnetic ordering at 2.8 K at ambient pressure. High-pressure AC susceptibility measurement on Ca-doped crystal showed a sharp superconducting transition at 2 K under 40 kbars. Tc onset reached a maximum value of 9.9 K at 54 kbars. The bulk superconductivity of the sample is confirmed by the high-pressure AC calorimetry with Tc max=9.4 K and TN=5 K at 56 kbars.

Observability of conduction electron spin resonance (CESR) in superconductors

The condition for the observability of CESR in superconducting thin films is analysed taking into account the finiteness of the flux penetration depth. We have explicitly evaluated the path-dependent phase mixing factor occuring in the expression for power absorption. The calculated line width turns out to be of the order of, or larger than, the nominal resonance frequency for the experimentally realisable choice of parameters.

On the determination of energy eigenvalues and coupling strengths using duality

The Shifman-Vainshtein-Zakharov method of determining the eigenvalues and coupling strengths, from the operator product expansion, for the current correlation functions is studied in the nonrelativistic context, using the semiclassical expansion. The relationship between the low-lying eigenvalues, and the leading corrections to the imaginary-time Green function is elucidated by comparing systems which have almost identical spectra. In the case of an anharmonic oscillator it is found that with the procedure stated in the paper, that inclusion of more terms to the asymptotic expansion does not show any simple trend towards convergence to the exact values. Generalization to higher partial waves is given. In particular for the P-level of the oscillator, the procedure gives poorer results than for the S-level, although the ratio of the two comes out much better.

Investigation of biferroic properties in La0.6Sr0.4MnO3/0.7Pb(Mg1/3Nb2/3)O3â0.3PbTiO3 epitaxial bilayered heterostructures

Epitaxial bilayered thin films consisting of La0.6Sr0.4MnO3 (LSMO) and 0.7Pb(Mg1/3Nb2/3)O3â0.3PbTiO3 (PMN-PT) layers of relatively different thicknesses were fabricated on LaNiO3 coated LaAlO3 (100) single crystal substrates by pulsed laser ablation technique. The crystallinity, ferroelectric, ferromagnetic, and magnetodielectric properties have been studied for all the bilayered heterostructures. Their microstructural analysis suggested possible StranskiâKrastanov type of growth mechanism in the present case. Ferroelectric and ferromagnetic characteristics of these bilayered heterostructures over a wide range of temperatures confirmed their biferroic nature. The magnetization and ferroelectric polarization of the bilayered heterostructures were enhanced with increasing PMN-PT layer thickness owing to the effect of lattice strain. In addition, evolution of the ferroelectric and ferromagnetic properties of these heterostructures with changing thicknesses of the PMN-PT and LSMO layers indicated possible influence of several interfacial effects such as space charge, depolarization field, domain wall pinning, and spin disorder on the observed properties. Dielectric properties of these heterostructures studied over a wide range of temperatures under different magnetic field strengths suggested a possible role of elastic strain mediated magnetoelectric coupling behind the observed magnetodielectric effect in addition to the influence of rearrangement of the interfacial charge carriers under an applied magnetic field.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g = 2.085, g =2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu S bonds. The experimentally determined hyperfine constants are A =34.9×10−4 cm−1, B =26.1×10−4 cm−1, A =60.4×10−4 cm−1, B =55.5×10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the bond, the bonds are also strongly covalent. ©1973 The American Institute of Physics

Nonlinear mode coupling of surface acoustic waves on an isotropic solid

The nonlinear mode coupling between two co-directional quasi-harmonic Rayleigh surface waves on an isotropic solid is analysed using the method of multiple scales. This procedure yields a system of six semi-linear hyperbolic partial differential equations with the same principal part governing the slow variations in the (complex) amplitudes of the two fundamental, the two second harmonic and the two combination frequency waves at the second stage of the perturbation expansion. A numerical solution of these equations for excitation by monochromatic signals at two arbitrary frequencies, indicates that there is a continuous transfer of energy back and forth among the fundamental, second harmonic and combination frequency waves due to mode coupling. The mode coupling tends to be more pronounced as the frequencies of the interacting waves approach each other.

Localised spin wave modes in a Heisenberg ferromagnet with biquadratic interaction

The presence of biquadratic exchange in a one-dimensional ferromagnetic Heisenberg chain with an impurity spin is shown to change the nature of the impurity modes and its eigenvalues considerably which can be observed experimentally.

Electron spin resonance study of copper(II) doped ferroelectric ammonium sulphate

Single crystal electron spin resonance studies of Cu2+ doped ferroelectric ammonium sulphate ((NH4)2SO4, Tc = 223 K) are reported at 300 and 77 K. The Cu2+ ion is found to enter the lattice interstitially with a trigonal bipyramidal coordination. Proton superhyperfine interaction is found for magnetic field directions close to the a-axis. Changes are observed in the 77 K recordings indicating a distortion of the trigonal bipyramid consistent with crystal structure data. An increase of the proton superhyperfine constant in the ferroelectric phase is indicative of stronger hydrogen bonding. The Cu2+ ion doped as an impurity in a trigonal bipyramid environment in a diamagnetic host lattice is reported for the first time.

Application of the Conjugate Gradient Method to a Problem on Minimum Time Orbit Transfer

This correspondence considers the problem of optimally controlling the thrust steering angle of an ion-propelled spaceship so as to effect a minimum time coplanar orbit transfer from the mean orbital distance of Earth to mean Martian and Venusian orbital distances. This problem has been modelled as a free terminal time-optimal control problem with unbounded control variable and with state variable equality constraints at the final time. The problem has been solved by the penalty function approach, using the conjugate gradient algorithm. In general, the optimal solution shows a significant departure from earlier work. In particular, the optimal control in the case of Earth-Mars orbit transfer, during the initial phase of the spaceship's flight, is found to be negative, resulting in the motion of the spaceship within the Earth's orbit for a significant fraction of the total optimized orbit transfer time. Such a feature exhibited by the optimal solution has not been reported at all by earlier investigators of this problem.

Dielectric and Electron Spin Resonance Spectroscopic Studies of Glassy Crystalline States of Organic Compounds

Dielectric studies of the glassy crystalline states of cyclohexanol, cyclohexanone, and camphor obtained by upercooling the plastic crystalline phase demonstrate the presence of characteristic a- and p-relaxations. The parameters of the a-relaxation fit the Vogel-Tammann-Fulcher (VTF) equation. ESR spin-probe studies of the glassy crystalline phase of cyclohexanol show that there is a marked decrease in the correlation time above the glasslike transition temperature. The present studies suggest the similarity between glassy crystals having long-range orientational disorder and glasses which are known to betra nslationally disordered.

Pyrrolidine ring conformations in prolyl peptides from 13C spin-lattice relaxation times

A method was developed in the framework of a bistable jump model to obtain the pyrrolidine ring conformations in proline peptides from 13C spin-lattice relaxation times. Equations are presented expressing the ring torsions in terms of the 13C spin-lattice relaxation times of the ring carbons. This method was applied to 26 pyrrolidine ring systems and acceptable conformations were obtained.

Antiferromagnetic spin-wave states in a linear chain with nearest- and next-nearest-neighbour interactions

The spectrum of short-closed chains up to N=12 are studied by exact diagonalization to obtain the spin-wave spectrum of the Hamiltonian H=2J Sigma i=1Nsi.si+1+2J alpha Sigma i=1Nsi.si+2, -1.0or=0.3 and alpha